Struct Scene 

pub struct Scene { /* private fields */ }

Top-level scene container. Holds a flat collection of grids keyed by GridId.

S2.0 only exposes registration / removal / lookup. Address math helpers (S2.x), edit API (S2.x), and rendering composition (S3) land in later sub-substages.

Implementations

impl Scene

pub fn to_snapshot(&self) -> SceneSnapshot

Capture the scene’s full state as a serde-friendly value. Each chunk is encoded via roxlap_formats::vxl::serialize; the rest is plain field data.

Grid iteration order in the produced snapshot is sorted by GridId so two snapshots of the same scene produce byte-identical output (the live HashMap iteration order would be non-deterministic).

pub fn from_snapshot(snap: &SceneSnapshot) -> Result<Self, FromSnapshotError>

Restore a Scene from a snapshot. Each chunk’s bytes are re-parsed via roxlap_formats::vxl::parse and re-armed for edits via roxlap_formats::vxl::Vxl::reserve_edit_capacity.

Errors

Returns FromSnapshotError::ChunkParse tagged with the owning grid + chunk index if any chunk’s bytes fail to parse. The partial scene is dropped — restoration is all-or-nothing.

impl Scene

pub fn save_snapshot(&self) -> Vec<u8>

Serialise the scene to the versioned snapshot wire format (QE.5b): SNAPSHOT_MAGIC + little-endian SNAPSHOT_VERSION + a bincode SceneSnapshot payload. This is the save-file API — a blob written today stays loadable by future engine versions (Self::load_snapshot dispatches on the version), which bare serde values can’t promise under positional codecs.

Hosts that want a different payload codec (JSON for debugging, postcard for size) can still serialise Self::to_snapshot’s value themselves — and then own their format’s evolution story.

Examples found in repository

examples/book_scene_graph.rs (line 152)

fn main() {
    // ANCHOR: scene_grids
    let mut scene = Scene::new();
    // A static "world" grid at the origin…
    let ground_id = scene.add_grid(GridTransform::at(DVec3::ZERO));
    // …and a second grid placed and rotated independently — its own
    // f64 world position + quaternion, same chunked voxel payload.
    let ship_id = scene.add_grid(GridTransform {
        origin: DVec3::new(300.0, -80.0, -40.0),
        rotation: DQuat::from_rotation_z(0.5),
        voxel_world_size: 1.0,
    });
    // Object grids should not paint their own (grid-local, rotating)
    // sky — leave the sky to the world grid.
    scene.grid_mut(ship_id).expect("just added").render_sky = false;
    // ANCHOR_END: scene_grids

    // ANCHOR: edits
    let ground = scene.grid_mut(ground_id).expect("just added");
    // Solid slab: grid-local voxel coords, inclusive on both ends,
    // decomposed across as many chunks as it spans (here 4×4).
    ground.set_rect(
        IVec3::new(-200, -200, 200),
        IVec3::new(199, 199, 254),
        Some(GRASS),
    );
    // `Some(colour)` inserts, `None` carves back to air.
    ground.set_sphere(IVec3::new(0, 0, 195), 12, Some(STONE));
    ground.set_rect(IVec3::new(-3, -200, 190), IVec3::new(3, 199, 196), None);
    // ANCHOR_END: edits

    // ANCHOR: queries
    // Solid tests: inside the slab, then inside the carved tunnel.
    assert!(ground.voxel_solid(IVec3::new(0, 0, 210)));
    assert!(!ground.voxel_solid(IVec3::new(0, 100, 193)));
    // Colour queries answer on surface voxels; deep interior cells
    // are untextured in the slab format and read as `None`.
    assert_eq!(ground.voxel_color(IVec3::new(50, 50, 200)), Some(GRASS));
    // ANCHOR_END: queries

    // ANCHOR: recolour
    // GOTCHA: inserting over already-solid voxels does NOT repaint
    // them — span insertion only fills air. Recolour = carve, then
    // insert.
    let (lo, hi) = (IVec3::new(20, 20, 200), IVec3::new(24, 24, 204));
    ground.set_rect(lo, hi, Some(RED));
    assert_eq!(ground.voxel_color(IVec3::new(22, 22, 200)), Some(GRASS)); // unchanged!
    ground.set_rect(lo, hi, None); // carve…
    ground.set_rect(lo, hi, Some(RED)); // …then insert
    assert_eq!(ground.voxel_color(IVec3::new(22, 22, 200)), Some(RED));
    // ANCHOR_END: recolour

    // ANCHOR: colfunc
    // A carve exposes fresh interior walls; the plain edits paint
    // them colour 0 (black). The `_with_colfunc` variants ask a
    // closure instead — it sees grid-local coordinates, so gradients
    // stay continuous across chunk seams. Here: a crater whose walls
    // darken with depth.
    ground.set_sphere_with_colfunc(IVec3::new(60, 60, 200), 8, SpanOp::Carve, |_x, _y, z| {
        let depth = (z - 192).clamp(0, 15) as u8;
        VoxColor::rgb(0x6b, 0x40 + depth * 3, 0x2f)
    });
    // ANCHOR_END: colfunc

    // ANCHOR: snapshot
    // Name grids before saving: ids survive the round-trip, but the
    // generator / store hooks are host code and cannot be serialised
    // — the name is your key for rebinding them after a load.
    scene.grid_mut(ground_id).expect("ground exists").name = Some("ground".into());
    let bytes = scene.save_snapshot(); // versioned envelope
    let restored = Scene::load_snapshot(&bytes).expect("self-authored snapshot");
    assert_eq!(restored.grid_count(), 2);
    let (_, ground2) = restored
        .grids()
        .find(|(_, g)| g.name.as_deref() == Some("ground"))
        .expect("rebind by name");
    assert_eq!(ground2.voxel_color(IVec3::new(22, 22, 200)), Some(RED));
    // ANCHOR_END: snapshot

    // ANCHOR: streaming
    // Streaming: attach a generator + radii to a grid, then pump once
    // per frame with the camera's world position. Chunks within
    // `r_active` stream in; chunks beyond `r_evict` drop out; the band
    // between is hysteresis so a camera hovering on a boundary
    // doesn't thrash.
    let stream_id = scene.add_grid(GridTransform::at(DVec3::new(0.0, 4096.0, 0.0)));
    let store = Arc::new(MemoryStore::default());
    let grid = scene.grid_mut(stream_id).expect("just added");
    grid.set_generator(Some(Arc::new(FloorGenerator)));
    grid.set_chunk_store(Some(store));
    grid.stream_radius = StreamRadius::new(256.0, 384.0);

    let camera_near = DVec3::new(0.0, 4096.0, 100.0);
    scene.pump_streaming_sync(camera_near); // real games: `pump_streaming`
    let grid = scene.grid(stream_id).expect("still there");
    assert!(grid.chunk_count() > 0); // floor streamed in around the camera
    assert!(grid.voxel_solid(IVec3::new(5, 5, 240)));
    // ANCHOR_END: streaming

    // ANCHOR: streaming_edit
    // Edit the streamed floor, walk far away, come back. The active
    // set follows the camera: the old region evicts (edited chunks
    // are handed to the ChunkStore first) while a fresh set streams
    // in around the new position. On return the store wins over the
    // generator, so the edit survives; without a store, eviction
    // would silently revert the chunk to generator output.
    scene
        .grid_mut(stream_id)
        .expect("still there")
        .set_voxel(IVec3::new(5, 5, 240), None); // dig a hole
    scene.pump_streaming_sync(camera_near + DVec3::new(0.0, 100_000.0, 0.0));
    let grid = scene.grid(stream_id).expect("still there");
    assert!(grid.chunk(IVec3::ZERO).is_none()); // home chunk evicted…
    assert!(grid.chunk_count() > 0); // …but the far region streamed in
    scene.pump_streaming_sync(camera_near);
    let grid = scene.grid(stream_id).expect("re-streamed");
    // The hole survived evict + re-stream.
    assert!(!grid.voxel_solid(IVec3::new(5, 5, 240)));
    // ANCHOR_END: streaming_edit

    // ANCHOR: grid_scale
    // Per-grid scale: `voxel_world_size` is world units per voxel. A grid
    // built with `at_scale(origin, 2.0)` has voxels twice world size — a
    // coarse "planet" — while `0.25` gives a fine detail grid; both coexist
    // at their true relative sizes. Only the world↔grid boundary scales:
    // edits + queries stay in voxels, unchanged.
    let mut scaled = Scene::new();
    let planet = scaled.add_grid(GridTransform::at_scale(DVec3::ZERO, 2.0));
    scaled
        .grid_mut(planet)
        .expect("just added")
        // Same voxel edit API — grid-local coordinates.
        .set_voxel(IVec3::new(5, 5, 10), Some(STONE));
    // Grid-local voxel z=10 sits at WORLD z = 20 (10 voxels × 2.0). A world
    // raycast down that column reports the grid-local voxel it hit AND a
    // WORLD-space `t` — so hits across grids of different scale compare
    // correctly (the raycaster marches voxels but returns world distance).
    let hit = scaled
        .raycast(DVec3::new(11.0, 11.0, 0.0), DVec3::new(0.0, 0.0, 1.0), 64.0)
        .expect("ray hits the scaled voxel");
    assert_eq!(hit.voxel, IVec3::new(5, 5, 10)); // grid-local, unscaled
    assert!((hit.t - 20.0).abs() < 1e-4); // WORLD distance: 10 voxels × 2.0
                                          // ANCHOR_END: grid_scale

    println!("book_scene_graph: all scene-graph assertions hold");
}

pub fn load_snapshot(bytes: &[u8]) -> Result<Self, SnapshotLoadError>

Load a scene from Self::save_snapshot bytes, dispatching on the embedded wire version.

Migration note: saves written before QE.5b (bare bincode of a SceneSnapshot, no envelope) fail with SnapshotLoadError::BadMagic; decode those with the engine version that wrote them and re-save.

Errors

SnapshotLoadError — bad magic, unknown version, corrupted payload, or a failing chunk restore.

Examples found in repository

examples/book_scene_graph.rs (line 153)

fn main() {
    // ANCHOR: scene_grids
    let mut scene = Scene::new();
    // A static "world" grid at the origin…
    let ground_id = scene.add_grid(GridTransform::at(DVec3::ZERO));
    // …and a second grid placed and rotated independently — its own
    // f64 world position + quaternion, same chunked voxel payload.
    let ship_id = scene.add_grid(GridTransform {
        origin: DVec3::new(300.0, -80.0, -40.0),
        rotation: DQuat::from_rotation_z(0.5),
        voxel_world_size: 1.0,
    });
    // Object grids should not paint their own (grid-local, rotating)
    // sky — leave the sky to the world grid.
    scene.grid_mut(ship_id).expect("just added").render_sky = false;
    // ANCHOR_END: scene_grids

    // ANCHOR: edits
    let ground = scene.grid_mut(ground_id).expect("just added");
    // Solid slab: grid-local voxel coords, inclusive on both ends,
    // decomposed across as many chunks as it spans (here 4×4).
    ground.set_rect(
        IVec3::new(-200, -200, 200),
        IVec3::new(199, 199, 254),
        Some(GRASS),
    );
    // `Some(colour)` inserts, `None` carves back to air.
    ground.set_sphere(IVec3::new(0, 0, 195), 12, Some(STONE));
    ground.set_rect(IVec3::new(-3, -200, 190), IVec3::new(3, 199, 196), None);
    // ANCHOR_END: edits

    // ANCHOR: queries
    // Solid tests: inside the slab, then inside the carved tunnel.
    assert!(ground.voxel_solid(IVec3::new(0, 0, 210)));
    assert!(!ground.voxel_solid(IVec3::new(0, 100, 193)));
    // Colour queries answer on surface voxels; deep interior cells
    // are untextured in the slab format and read as `None`.
    assert_eq!(ground.voxel_color(IVec3::new(50, 50, 200)), Some(GRASS));
    // ANCHOR_END: queries

    // ANCHOR: recolour
    // GOTCHA: inserting over already-solid voxels does NOT repaint
    // them — span insertion only fills air. Recolour = carve, then
    // insert.
    let (lo, hi) = (IVec3::new(20, 20, 200), IVec3::new(24, 24, 204));
    ground.set_rect(lo, hi, Some(RED));
    assert_eq!(ground.voxel_color(IVec3::new(22, 22, 200)), Some(GRASS)); // unchanged!
    ground.set_rect(lo, hi, None); // carve…
    ground.set_rect(lo, hi, Some(RED)); // …then insert
    assert_eq!(ground.voxel_color(IVec3::new(22, 22, 200)), Some(RED));
    // ANCHOR_END: recolour

    // ANCHOR: colfunc
    // A carve exposes fresh interior walls; the plain edits paint
    // them colour 0 (black). The `_with_colfunc` variants ask a
    // closure instead — it sees grid-local coordinates, so gradients
    // stay continuous across chunk seams. Here: a crater whose walls
    // darken with depth.
    ground.set_sphere_with_colfunc(IVec3::new(60, 60, 200), 8, SpanOp::Carve, |_x, _y, z| {
        let depth = (z - 192).clamp(0, 15) as u8;
        VoxColor::rgb(0x6b, 0x40 + depth * 3, 0x2f)
    });
    // ANCHOR_END: colfunc

    // ANCHOR: snapshot
    // Name grids before saving: ids survive the round-trip, but the
    // generator / store hooks are host code and cannot be serialised
    // — the name is your key for rebinding them after a load.
    scene.grid_mut(ground_id).expect("ground exists").name = Some("ground".into());
    let bytes = scene.save_snapshot(); // versioned envelope
    let restored = Scene::load_snapshot(&bytes).expect("self-authored snapshot");
    assert_eq!(restored.grid_count(), 2);
    let (_, ground2) = restored
        .grids()
        .find(|(_, g)| g.name.as_deref() == Some("ground"))
        .expect("rebind by name");
    assert_eq!(ground2.voxel_color(IVec3::new(22, 22, 200)), Some(RED));
    // ANCHOR_END: snapshot

    // ANCHOR: streaming
    // Streaming: attach a generator + radii to a grid, then pump once
    // per frame with the camera's world position. Chunks within
    // `r_active` stream in; chunks beyond `r_evict` drop out; the band
    // between is hysteresis so a camera hovering on a boundary
    // doesn't thrash.
    let stream_id = scene.add_grid(GridTransform::at(DVec3::new(0.0, 4096.0, 0.0)));
    let store = Arc::new(MemoryStore::default());
    let grid = scene.grid_mut(stream_id).expect("just added");
    grid.set_generator(Some(Arc::new(FloorGenerator)));
    grid.set_chunk_store(Some(store));
    grid.stream_radius = StreamRadius::new(256.0, 384.0);

    let camera_near = DVec3::new(0.0, 4096.0, 100.0);
    scene.pump_streaming_sync(camera_near); // real games: `pump_streaming`
    let grid = scene.grid(stream_id).expect("still there");
    assert!(grid.chunk_count() > 0); // floor streamed in around the camera
    assert!(grid.voxel_solid(IVec3::new(5, 5, 240)));
    // ANCHOR_END: streaming

    // ANCHOR: streaming_edit
    // Edit the streamed floor, walk far away, come back. The active
    // set follows the camera: the old region evicts (edited chunks
    // are handed to the ChunkStore first) while a fresh set streams
    // in around the new position. On return the store wins over the
    // generator, so the edit survives; without a store, eviction
    // would silently revert the chunk to generator output.
    scene
        .grid_mut(stream_id)
        .expect("still there")
        .set_voxel(IVec3::new(5, 5, 240), None); // dig a hole
    scene.pump_streaming_sync(camera_near + DVec3::new(0.0, 100_000.0, 0.0));
    let grid = scene.grid(stream_id).expect("still there");
    assert!(grid.chunk(IVec3::ZERO).is_none()); // home chunk evicted…
    assert!(grid.chunk_count() > 0); // …but the far region streamed in
    scene.pump_streaming_sync(camera_near);
    let grid = scene.grid(stream_id).expect("re-streamed");
    // The hole survived evict + re-stream.
    assert!(!grid.voxel_solid(IVec3::new(5, 5, 240)));
    // ANCHOR_END: streaming_edit

    // ANCHOR: grid_scale
    // Per-grid scale: `voxel_world_size` is world units per voxel. A grid
    // built with `at_scale(origin, 2.0)` has voxels twice world size — a
    // coarse "planet" — while `0.25` gives a fine detail grid; both coexist
    // at their true relative sizes. Only the world↔grid boundary scales:
    // edits + queries stay in voxels, unchanged.
    let mut scaled = Scene::new();
    let planet = scaled.add_grid(GridTransform::at_scale(DVec3::ZERO, 2.0));
    scaled
        .grid_mut(planet)
        .expect("just added")
        // Same voxel edit API — grid-local coordinates.
        .set_voxel(IVec3::new(5, 5, 10), Some(STONE));
    // Grid-local voxel z=10 sits at WORLD z = 20 (10 voxels × 2.0). A world
    // raycast down that column reports the grid-local voxel it hit AND a
    // WORLD-space `t` — so hits across grids of different scale compare
    // correctly (the raycaster marches voxels but returns world distance).
    let hit = scaled
        .raycast(DVec3::new(11.0, 11.0, 0.0), DVec3::new(0.0, 0.0, 1.0), 64.0)
        .expect("ray hits the scaled voxel");
    assert_eq!(hit.voxel, IVec3::new(5, 5, 10)); // grid-local, unscaled
    assert!((hit.t - 20.0).abs() < 1e-4); // WORLD distance: 10 voxels × 2.0
                                          // ANCHOR_END: grid_scale

    println!("book_scene_graph: all scene-graph assertions hold");
}

impl Scene

pub fn water_depth_at(&self, world: DVec3) -> Option<(GridId, f64)>

Depth of a world-space point below a water surface, in world units, with the grid that owns the deepest water at that point. None when no grid’s water contains the point.

The world↔grid boundary rule (SC) applies: the point is converted into each grid’s local voxel frame (un-rotate, un-translate, / voxel_world_size), the depth is measured along the grid’s local z (world-vertical for the usual identity/yaw-only water grids), and converted back to world units (× voxel_world_size).

Deterministic: on an exact depth tie between grids (two identity grids sharing a waterline at their seam), the smallest GridId wins — Scene::grids iterates a HashMap, so without the explicit tie-break the winner would flip between runs (and WT.2/WT.3 hang per-grid state off this id).

pub fn in_water(&self, world: DVec3) -> bool

true when the world-space point is inside any water volume. Short-circuits on the first hit — the query the swim state (WT.1) runs per actor per frame; use Self::water_depth_at only when the depth is needed.

impl Scene

pub fn new() -> Self

New empty scene — no grids.

Examples found in repository

examples/book_controller.rs (line 30)

fn build_world() -> Scene {
    let mut scene = Scene::new();
    let id = scene.add_grid(GridTransform::identity());
    let g = scene.grid_mut(id).expect("grid");
    // Ground slab: surface plane at z = 100 (+z is down, so the
    // slab fills downward).
    g.set_rect(
        IVec3::new(20, 20, 100),
        IVec3::new(140, 140, 120),
        Some(VoxColor::rgb(0x4d, 0x8a, 0x3a)),
    );
    // A 1-voxel ledge to step onto, and a wall to slide along.
    g.set_rect(
        IVec3::new(90, 20, 99),
        IVec3::new(140, 140, 99),
        Some(VoxColor::rgb(0x77, 0x66, 0x55)),
    );
    g.set_rect(
        IVec3::new(60, 70, 60),
        IVec3::new(62, 140, 99),
        Some(VoxColor::rgb(0x88, 0x44, 0x44)),
    );
    // A water curtain the veto lets the body wade through. Two
    // format facts (both pinned as engine tests): pass-through
    // geometry works up to 2 voxels thick — thicker walls grow a
    // colourless UnexposedSolid core no veto can classify — and
    // must sit ≥ 1 voxel inside the chunk (edge voxels lose their
    // side colours).
    g.set_rect(IVec3::new(40, 40, 80), IVec3::new(41, 60, 99), Some(WATER));
    scene
}

fn main() {
    let scene = build_world();

    // ANCHOR: setup
    // A walking body: a feet-positioned collision box, f64 world.
    // Distances are voxels, times seconds; +z is DOWN, so gravity is
    // positive and a jump impulse negative.
    let mut body = CharacterBody::new(CharacterDef {
        radius: 0.4,      // xy half-extent of the box
        height: 1.8,      // feet → head (toward -z)
        eye_height: 1.62, // feet → camera anchor
        step_up: 1.05,    // auto-step ledges up to 1 voxel
        solidity: Solidity {
            bedrock_blocks: false, // match your renderer's policy
            passable: Some(water_passes),
        },
        ..CharacterDef::default()
    });
    body.teleport(DVec3::new(50.0, 50.0, 95.0)); // FEET position
                                                 // ANCHOR_END: setup

    // ANCHOR: frame
    // Per frame: build a wish direction from input (unit-length or
    // zero — walk() clamps), call walk() EVERY frame (a zero wish is
    // what stops the body), then anchor the camera at the eye.
    let dt = 1.0 / 60.0;
    for frame in 0..480 {
        let input = WalkInput {
            wish: DVec3::new(1.0, 0.2, 0.0), // toward the ledge
            jump: frame == 120,              // one hop on the way
            ..WalkInput::default()           // sink (WT.1) + future fields
        };
        body.walk(&scene, dt, input);
    }
    let eye = body.eye_pos(); // = Camera::from_yaw_pitch(eye.into(), yaw, pitch)
                              // ANCHOR_END: frame

    // The trajectory the walk above promises, pinned:
    assert!(body.on_ground(), "settled after the hop");
    // It fell to the floor plane, then stepped up the 1-voxel ledge
    // (surface z = 99) while walking +x.
    assert!(body.pos().x > 90.0, "reached the ledge region");
    assert!(
        (body.pos().z - 99.0).abs() < 0.01,
        "standing on the ledge, feet at {}",
        body.pos().z
    );
    assert!(eye.z < body.pos().z, "the eye is above the feet (-z is up)");

    // Fly mode is the demos' free camera: no gravity, full-3D wish,
    // instant start/stop, still sliding along walls.
    body.set_mode(MoveMode::Fly);
    body.walk(&scene, dt, WalkInput::default());
    assert_eq!(body.vel(), DVec3::ZERO, "fly idles in place");

    // The water curtain from `build_world` is passable: probe the
    // veto directly (the same query walk() uses).
    let wading = roxlap_scene::box_overlaps_solid(
        &scene,
        DVec3::new(40.2, 50.0, 90.0),
        DVec3::new(40.8, 50.6, 91.8),
        body.def().solidity,
    );
    assert!(!wading, "water is passable under the veto");

    swim_demo();

    println!("book_controller: all controller assertions hold");
}

/// WT — the water + swimming section's snippets: a deep pool the body
/// falls into, floats in, dives through and breaches out of.
fn swim_demo() {
    // ANCHOR: water
    // Physics water is a WaterVolume on the grid — a grid-local voxel
    // AABB whose TOP face (min z — +z is down) is the surface. It is
    // independent of the voxels: fill the same region with a
    // volumetric-material shell for the visuals, or don't.
    let mut scene = Scene::new();
    let id = scene.add_grid(GridTransform::identity());
    let g = scene.grid_mut(id).expect("grid");
    // Basin floor, then 20 voxels of water above it (surface z = 100).
    g.set_rect(
        IVec3::new(20, 20, 120),
        IVec3::new(140, 140, 130),
        Some(VoxColor::rgb(0x50, 0x90, 0x50)),
    );
    g.add_water_volume(IVec3::new(20, 20, 100), IVec3::new(140, 140, 119));

    // A Walk-mode body dropped in swims AUTOMATICALLY once submerged
    // past `swim_enter_frac` of its height: buoyancy floats it to a
    // bob at the surface, `jump` strokes up, `sink` strokes down, and
    // a jump with the head above water breaches.
    let mut body = CharacterBody::new(CharacterDef::default());
    body.teleport(DVec3::new(80.0, 80.0, 115.0)); // deep in the pool
    for _ in 0..600 {
        body.walk(&scene, 1.0 / 60.0, WalkInput::default());
    }
    assert!(body.is_swimming(), "floated to the surface bob");
    assert!(!body.eye_in_water(&scene), "bobbing: the camera is dry");

    // Dive: hold `sink`. The submerged EYE is the hook for the
    // underwater feel — drive the WT.2 frame tint and the WT.3
    // listener lowpass from this one flag.
    for _ in 0..90 {
        body.walk(
            &scene,
            1.0 / 60.0,
            WalkInput {
                sink: true,
                ..WalkInput::default()
            },
        );
    }
    assert!(body.eye_in_water(&scene), "diving: tint + muffle now");
    // ANCHOR_END: water
}

examples/book_scene_graph.rs (line 85)

fn main() {
    // ANCHOR: scene_grids
    let mut scene = Scene::new();
    // A static "world" grid at the origin…
    let ground_id = scene.add_grid(GridTransform::at(DVec3::ZERO));
    // …and a second grid placed and rotated independently — its own
    // f64 world position + quaternion, same chunked voxel payload.
    let ship_id = scene.add_grid(GridTransform {
        origin: DVec3::new(300.0, -80.0, -40.0),
        rotation: DQuat::from_rotation_z(0.5),
        voxel_world_size: 1.0,
    });
    // Object grids should not paint their own (grid-local, rotating)
    // sky — leave the sky to the world grid.
    scene.grid_mut(ship_id).expect("just added").render_sky = false;
    // ANCHOR_END: scene_grids

    // ANCHOR: edits
    let ground = scene.grid_mut(ground_id).expect("just added");
    // Solid slab: grid-local voxel coords, inclusive on both ends,
    // decomposed across as many chunks as it spans (here 4×4).
    ground.set_rect(
        IVec3::new(-200, -200, 200),
        IVec3::new(199, 199, 254),
        Some(GRASS),
    );
    // `Some(colour)` inserts, `None` carves back to air.
    ground.set_sphere(IVec3::new(0, 0, 195), 12, Some(STONE));
    ground.set_rect(IVec3::new(-3, -200, 190), IVec3::new(3, 199, 196), None);
    // ANCHOR_END: edits

    // ANCHOR: queries
    // Solid tests: inside the slab, then inside the carved tunnel.
    assert!(ground.voxel_solid(IVec3::new(0, 0, 210)));
    assert!(!ground.voxel_solid(IVec3::new(0, 100, 193)));
    // Colour queries answer on surface voxels; deep interior cells
    // are untextured in the slab format and read as `None`.
    assert_eq!(ground.voxel_color(IVec3::new(50, 50, 200)), Some(GRASS));
    // ANCHOR_END: queries

    // ANCHOR: recolour
    // GOTCHA: inserting over already-solid voxels does NOT repaint
    // them — span insertion only fills air. Recolour = carve, then
    // insert.
    let (lo, hi) = (IVec3::new(20, 20, 200), IVec3::new(24, 24, 204));
    ground.set_rect(lo, hi, Some(RED));
    assert_eq!(ground.voxel_color(IVec3::new(22, 22, 200)), Some(GRASS)); // unchanged!
    ground.set_rect(lo, hi, None); // carve…
    ground.set_rect(lo, hi, Some(RED)); // …then insert
    assert_eq!(ground.voxel_color(IVec3::new(22, 22, 200)), Some(RED));
    // ANCHOR_END: recolour

    // ANCHOR: colfunc
    // A carve exposes fresh interior walls; the plain edits paint
    // them colour 0 (black). The `_with_colfunc` variants ask a
    // closure instead — it sees grid-local coordinates, so gradients
    // stay continuous across chunk seams. Here: a crater whose walls
    // darken with depth.
    ground.set_sphere_with_colfunc(IVec3::new(60, 60, 200), 8, SpanOp::Carve, |_x, _y, z| {
        let depth = (z - 192).clamp(0, 15) as u8;
        VoxColor::rgb(0x6b, 0x40 + depth * 3, 0x2f)
    });
    // ANCHOR_END: colfunc

    // ANCHOR: snapshot
    // Name grids before saving: ids survive the round-trip, but the
    // generator / store hooks are host code and cannot be serialised
    // — the name is your key for rebinding them after a load.
    scene.grid_mut(ground_id).expect("ground exists").name = Some("ground".into());
    let bytes = scene.save_snapshot(); // versioned envelope
    let restored = Scene::load_snapshot(&bytes).expect("self-authored snapshot");
    assert_eq!(restored.grid_count(), 2);
    let (_, ground2) = restored
        .grids()
        .find(|(_, g)| g.name.as_deref() == Some("ground"))
        .expect("rebind by name");
    assert_eq!(ground2.voxel_color(IVec3::new(22, 22, 200)), Some(RED));
    // ANCHOR_END: snapshot

    // ANCHOR: streaming
    // Streaming: attach a generator + radii to a grid, then pump once
    // per frame with the camera's world position. Chunks within
    // `r_active` stream in; chunks beyond `r_evict` drop out; the band
    // between is hysteresis so a camera hovering on a boundary
    // doesn't thrash.
    let stream_id = scene.add_grid(GridTransform::at(DVec3::new(0.0, 4096.0, 0.0)));
    let store = Arc::new(MemoryStore::default());
    let grid = scene.grid_mut(stream_id).expect("just added");
    grid.set_generator(Some(Arc::new(FloorGenerator)));
    grid.set_chunk_store(Some(store));
    grid.stream_radius = StreamRadius::new(256.0, 384.0);

    let camera_near = DVec3::new(0.0, 4096.0, 100.0);
    scene.pump_streaming_sync(camera_near); // real games: `pump_streaming`
    let grid = scene.grid(stream_id).expect("still there");
    assert!(grid.chunk_count() > 0); // floor streamed in around the camera
    assert!(grid.voxel_solid(IVec3::new(5, 5, 240)));
    // ANCHOR_END: streaming

    // ANCHOR: streaming_edit
    // Edit the streamed floor, walk far away, come back. The active
    // set follows the camera: the old region evicts (edited chunks
    // are handed to the ChunkStore first) while a fresh set streams
    // in around the new position. On return the store wins over the
    // generator, so the edit survives; without a store, eviction
    // would silently revert the chunk to generator output.
    scene
        .grid_mut(stream_id)
        .expect("still there")
        .set_voxel(IVec3::new(5, 5, 240), None); // dig a hole
    scene.pump_streaming_sync(camera_near + DVec3::new(0.0, 100_000.0, 0.0));
    let grid = scene.grid(stream_id).expect("still there");
    assert!(grid.chunk(IVec3::ZERO).is_none()); // home chunk evicted…
    assert!(grid.chunk_count() > 0); // …but the far region streamed in
    scene.pump_streaming_sync(camera_near);
    let grid = scene.grid(stream_id).expect("re-streamed");
    // The hole survived evict + re-stream.
    assert!(!grid.voxel_solid(IVec3::new(5, 5, 240)));
    // ANCHOR_END: streaming_edit

    // ANCHOR: grid_scale
    // Per-grid scale: `voxel_world_size` is world units per voxel. A grid
    // built with `at_scale(origin, 2.0)` has voxels twice world size — a
    // coarse "planet" — while `0.25` gives a fine detail grid; both coexist
    // at their true relative sizes. Only the world↔grid boundary scales:
    // edits + queries stay in voxels, unchanged.
    let mut scaled = Scene::new();
    let planet = scaled.add_grid(GridTransform::at_scale(DVec3::ZERO, 2.0));
    scaled
        .grid_mut(planet)
        .expect("just added")
        // Same voxel edit API — grid-local coordinates.
        .set_voxel(IVec3::new(5, 5, 10), Some(STONE));
    // Grid-local voxel z=10 sits at WORLD z = 20 (10 voxels × 2.0). A world
    // raycast down that column reports the grid-local voxel it hit AND a
    // WORLD-space `t` — so hits across grids of different scale compare
    // correctly (the raycaster marches voxels but returns world distance).
    let hit = scaled
        .raycast(DVec3::new(11.0, 11.0, 0.0), DVec3::new(0.0, 0.0, 1.0), 64.0)
        .expect("ray hits the scaled voxel");
    assert_eq!(hit.voxel, IVec3::new(5, 5, 10)); // grid-local, unscaled
    assert!((hit.t - 20.0).abs() < 1e-4); // WORLD distance: 10 voxels × 2.0
                                          // ANCHOR_END: grid_scale

    println!("book_scene_graph: all scene-graph assertions hold");
}

pub fn grid_count(&self) -> usize

Number of grids currently registered.

Examples found in repository

examples/book_scene_graph.rs (line 154)

fn main() {
    // ANCHOR: scene_grids
    let mut scene = Scene::new();
    // A static "world" grid at the origin…
    let ground_id = scene.add_grid(GridTransform::at(DVec3::ZERO));
    // …and a second grid placed and rotated independently — its own
    // f64 world position + quaternion, same chunked voxel payload.
    let ship_id = scene.add_grid(GridTransform {
        origin: DVec3::new(300.0, -80.0, -40.0),
        rotation: DQuat::from_rotation_z(0.5),
        voxel_world_size: 1.0,
    });
    // Object grids should not paint their own (grid-local, rotating)
    // sky — leave the sky to the world grid.
    scene.grid_mut(ship_id).expect("just added").render_sky = false;
    // ANCHOR_END: scene_grids

    // ANCHOR: edits
    let ground = scene.grid_mut(ground_id).expect("just added");
    // Solid slab: grid-local voxel coords, inclusive on both ends,
    // decomposed across as many chunks as it spans (here 4×4).
    ground.set_rect(
        IVec3::new(-200, -200, 200),
        IVec3::new(199, 199, 254),
        Some(GRASS),
    );
    // `Some(colour)` inserts, `None` carves back to air.
    ground.set_sphere(IVec3::new(0, 0, 195), 12, Some(STONE));
    ground.set_rect(IVec3::new(-3, -200, 190), IVec3::new(3, 199, 196), None);
    // ANCHOR_END: edits

    // ANCHOR: queries
    // Solid tests: inside the slab, then inside the carved tunnel.
    assert!(ground.voxel_solid(IVec3::new(0, 0, 210)));
    assert!(!ground.voxel_solid(IVec3::new(0, 100, 193)));
    // Colour queries answer on surface voxels; deep interior cells
    // are untextured in the slab format and read as `None`.
    assert_eq!(ground.voxel_color(IVec3::new(50, 50, 200)), Some(GRASS));
    // ANCHOR_END: queries

    // ANCHOR: recolour
    // GOTCHA: inserting over already-solid voxels does NOT repaint
    // them — span insertion only fills air. Recolour = carve, then
    // insert.
    let (lo, hi) = (IVec3::new(20, 20, 200), IVec3::new(24, 24, 204));
    ground.set_rect(lo, hi, Some(RED));
    assert_eq!(ground.voxel_color(IVec3::new(22, 22, 200)), Some(GRASS)); // unchanged!
    ground.set_rect(lo, hi, None); // carve…
    ground.set_rect(lo, hi, Some(RED)); // …then insert
    assert_eq!(ground.voxel_color(IVec3::new(22, 22, 200)), Some(RED));
    // ANCHOR_END: recolour

    // ANCHOR: colfunc
    // A carve exposes fresh interior walls; the plain edits paint
    // them colour 0 (black). The `_with_colfunc` variants ask a
    // closure instead — it sees grid-local coordinates, so gradients
    // stay continuous across chunk seams. Here: a crater whose walls
    // darken with depth.
    ground.set_sphere_with_colfunc(IVec3::new(60, 60, 200), 8, SpanOp::Carve, |_x, _y, z| {
        let depth = (z - 192).clamp(0, 15) as u8;
        VoxColor::rgb(0x6b, 0x40 + depth * 3, 0x2f)
    });
    // ANCHOR_END: colfunc

    // ANCHOR: snapshot
    // Name grids before saving: ids survive the round-trip, but the
    // generator / store hooks are host code and cannot be serialised
    // — the name is your key for rebinding them after a load.
    scene.grid_mut(ground_id).expect("ground exists").name = Some("ground".into());
    let bytes = scene.save_snapshot(); // versioned envelope
    let restored = Scene::load_snapshot(&bytes).expect("self-authored snapshot");
    assert_eq!(restored.grid_count(), 2);
    let (_, ground2) = restored
        .grids()
        .find(|(_, g)| g.name.as_deref() == Some("ground"))
        .expect("rebind by name");
    assert_eq!(ground2.voxel_color(IVec3::new(22, 22, 200)), Some(RED));
    // ANCHOR_END: snapshot

    // ANCHOR: streaming
    // Streaming: attach a generator + radii to a grid, then pump once
    // per frame with the camera's world position. Chunks within
    // `r_active` stream in; chunks beyond `r_evict` drop out; the band
    // between is hysteresis so a camera hovering on a boundary
    // doesn't thrash.
    let stream_id = scene.add_grid(GridTransform::at(DVec3::new(0.0, 4096.0, 0.0)));
    let store = Arc::new(MemoryStore::default());
    let grid = scene.grid_mut(stream_id).expect("just added");
    grid.set_generator(Some(Arc::new(FloorGenerator)));
    grid.set_chunk_store(Some(store));
    grid.stream_radius = StreamRadius::new(256.0, 384.0);

    let camera_near = DVec3::new(0.0, 4096.0, 100.0);
    scene.pump_streaming_sync(camera_near); // real games: `pump_streaming`
    let grid = scene.grid(stream_id).expect("still there");
    assert!(grid.chunk_count() > 0); // floor streamed in around the camera
    assert!(grid.voxel_solid(IVec3::new(5, 5, 240)));
    // ANCHOR_END: streaming

    // ANCHOR: streaming_edit
    // Edit the streamed floor, walk far away, come back. The active
    // set follows the camera: the old region evicts (edited chunks
    // are handed to the ChunkStore first) while a fresh set streams
    // in around the new position. On return the store wins over the
    // generator, so the edit survives; without a store, eviction
    // would silently revert the chunk to generator output.
    scene
        .grid_mut(stream_id)
        .expect("still there")
        .set_voxel(IVec3::new(5, 5, 240), None); // dig a hole
    scene.pump_streaming_sync(camera_near + DVec3::new(0.0, 100_000.0, 0.0));
    let grid = scene.grid(stream_id).expect("still there");
    assert!(grid.chunk(IVec3::ZERO).is_none()); // home chunk evicted…
    assert!(grid.chunk_count() > 0); // …but the far region streamed in
    scene.pump_streaming_sync(camera_near);
    let grid = scene.grid(stream_id).expect("re-streamed");
    // The hole survived evict + re-stream.
    assert!(!grid.voxel_solid(IVec3::new(5, 5, 240)));
    // ANCHOR_END: streaming_edit

    // ANCHOR: grid_scale
    // Per-grid scale: `voxel_world_size` is world units per voxel. A grid
    // built with `at_scale(origin, 2.0)` has voxels twice world size — a
    // coarse "planet" — while `0.25` gives a fine detail grid; both coexist
    // at their true relative sizes. Only the world↔grid boundary scales:
    // edits + queries stay in voxels, unchanged.
    let mut scaled = Scene::new();
    let planet = scaled.add_grid(GridTransform::at_scale(DVec3::ZERO, 2.0));
    scaled
        .grid_mut(planet)
        .expect("just added")
        // Same voxel edit API — grid-local coordinates.
        .set_voxel(IVec3::new(5, 5, 10), Some(STONE));
    // Grid-local voxel z=10 sits at WORLD z = 20 (10 voxels × 2.0). A world
    // raycast down that column reports the grid-local voxel it hit AND a
    // WORLD-space `t` — so hits across grids of different scale compare
    // correctly (the raycaster marches voxels but returns world distance).
    let hit = scaled
        .raycast(DVec3::new(11.0, 11.0, 0.0), DVec3::new(0.0, 0.0, 1.0), 64.0)
        .expect("ray hits the scaled voxel");
    assert_eq!(hit.voxel, IVec3::new(5, 5, 10)); // grid-local, unscaled
    assert!((hit.t - 20.0).abs() < 1e-4); // WORLD distance: 10 voxels × 2.0
                                          // ANCHOR_END: grid_scale

    println!("book_scene_graph: all scene-graph assertions hold");
}

pub fn add_grid(&mut self, transform: GridTransform) -> GridId

Register a new grid. Returns its fresh, unique GridId.

SC — debug-asserts transform.voxel_world_size is finite and > 0 (catches a direct GridTransform { .. } literal that bypasses GridTransform::at_scale); a 0 breaks the scaled marcher.

Examples found in repository

examples/book_controller.rs (line 31)

fn build_world() -> Scene {
    let mut scene = Scene::new();
    let id = scene.add_grid(GridTransform::identity());
    let g = scene.grid_mut(id).expect("grid");
    // Ground slab: surface plane at z = 100 (+z is down, so the
    // slab fills downward).
    g.set_rect(
        IVec3::new(20, 20, 100),
        IVec3::new(140, 140, 120),
        Some(VoxColor::rgb(0x4d, 0x8a, 0x3a)),
    );
    // A 1-voxel ledge to step onto, and a wall to slide along.
    g.set_rect(
        IVec3::new(90, 20, 99),
        IVec3::new(140, 140, 99),
        Some(VoxColor::rgb(0x77, 0x66, 0x55)),
    );
    g.set_rect(
        IVec3::new(60, 70, 60),
        IVec3::new(62, 140, 99),
        Some(VoxColor::rgb(0x88, 0x44, 0x44)),
    );
    // A water curtain the veto lets the body wade through. Two
    // format facts (both pinned as engine tests): pass-through
    // geometry works up to 2 voxels thick — thicker walls grow a
    // colourless UnexposedSolid core no veto can classify — and
    // must sit ≥ 1 voxel inside the chunk (edge voxels lose their
    // side colours).
    g.set_rect(IVec3::new(40, 40, 80), IVec3::new(41, 60, 99), Some(WATER));
    scene
}

fn main() {
    let scene = build_world();

    // ANCHOR: setup
    // A walking body: a feet-positioned collision box, f64 world.
    // Distances are voxels, times seconds; +z is DOWN, so gravity is
    // positive and a jump impulse negative.
    let mut body = CharacterBody::new(CharacterDef {
        radius: 0.4,      // xy half-extent of the box
        height: 1.8,      // feet → head (toward -z)
        eye_height: 1.62, // feet → camera anchor
        step_up: 1.05,    // auto-step ledges up to 1 voxel
        solidity: Solidity {
            bedrock_blocks: false, // match your renderer's policy
            passable: Some(water_passes),
        },
        ..CharacterDef::default()
    });
    body.teleport(DVec3::new(50.0, 50.0, 95.0)); // FEET position
                                                 // ANCHOR_END: setup

    // ANCHOR: frame
    // Per frame: build a wish direction from input (unit-length or
    // zero — walk() clamps), call walk() EVERY frame (a zero wish is
    // what stops the body), then anchor the camera at the eye.
    let dt = 1.0 / 60.0;
    for frame in 0..480 {
        let input = WalkInput {
            wish: DVec3::new(1.0, 0.2, 0.0), // toward the ledge
            jump: frame == 120,              // one hop on the way
            ..WalkInput::default()           // sink (WT.1) + future fields
        };
        body.walk(&scene, dt, input);
    }
    let eye = body.eye_pos(); // = Camera::from_yaw_pitch(eye.into(), yaw, pitch)
                              // ANCHOR_END: frame

    // The trajectory the walk above promises, pinned:
    assert!(body.on_ground(), "settled after the hop");
    // It fell to the floor plane, then stepped up the 1-voxel ledge
    // (surface z = 99) while walking +x.
    assert!(body.pos().x > 90.0, "reached the ledge region");
    assert!(
        (body.pos().z - 99.0).abs() < 0.01,
        "standing on the ledge, feet at {}",
        body.pos().z
    );
    assert!(eye.z < body.pos().z, "the eye is above the feet (-z is up)");

    // Fly mode is the demos' free camera: no gravity, full-3D wish,
    // instant start/stop, still sliding along walls.
    body.set_mode(MoveMode::Fly);
    body.walk(&scene, dt, WalkInput::default());
    assert_eq!(body.vel(), DVec3::ZERO, "fly idles in place");

    // The water curtain from `build_world` is passable: probe the
    // veto directly (the same query walk() uses).
    let wading = roxlap_scene::box_overlaps_solid(
        &scene,
        DVec3::new(40.2, 50.0, 90.0),
        DVec3::new(40.8, 50.6, 91.8),
        body.def().solidity,
    );
    assert!(!wading, "water is passable under the veto");

    swim_demo();

    println!("book_controller: all controller assertions hold");
}

/// WT — the water + swimming section's snippets: a deep pool the body
/// falls into, floats in, dives through and breaches out of.
fn swim_demo() {
    // ANCHOR: water
    // Physics water is a WaterVolume on the grid — a grid-local voxel
    // AABB whose TOP face (min z — +z is down) is the surface. It is
    // independent of the voxels: fill the same region with a
    // volumetric-material shell for the visuals, or don't.
    let mut scene = Scene::new();
    let id = scene.add_grid(GridTransform::identity());
    let g = scene.grid_mut(id).expect("grid");
    // Basin floor, then 20 voxels of water above it (surface z = 100).
    g.set_rect(
        IVec3::new(20, 20, 120),
        IVec3::new(140, 140, 130),
        Some(VoxColor::rgb(0x50, 0x90, 0x50)),
    );
    g.add_water_volume(IVec3::new(20, 20, 100), IVec3::new(140, 140, 119));

    // A Walk-mode body dropped in swims AUTOMATICALLY once submerged
    // past `swim_enter_frac` of its height: buoyancy floats it to a
    // bob at the surface, `jump` strokes up, `sink` strokes down, and
    // a jump with the head above water breaches.
    let mut body = CharacterBody::new(CharacterDef::default());
    body.teleport(DVec3::new(80.0, 80.0, 115.0)); // deep in the pool
    for _ in 0..600 {
        body.walk(&scene, 1.0 / 60.0, WalkInput::default());
    }
    assert!(body.is_swimming(), "floated to the surface bob");
    assert!(!body.eye_in_water(&scene), "bobbing: the camera is dry");

    // Dive: hold `sink`. The submerged EYE is the hook for the
    // underwater feel — drive the WT.2 frame tint and the WT.3
    // listener lowpass from this one flag.
    for _ in 0..90 {
        body.walk(
            &scene,
            1.0 / 60.0,
            WalkInput {
                sink: true,
                ..WalkInput::default()
            },
        );
    }
    assert!(body.eye_in_water(&scene), "diving: tint + muffle now");
    // ANCHOR_END: water
}

examples/book_scene_graph.rs (line 87)

fn main() {
    // ANCHOR: scene_grids
    let mut scene = Scene::new();
    // A static "world" grid at the origin…
    let ground_id = scene.add_grid(GridTransform::at(DVec3::ZERO));
    // …and a second grid placed and rotated independently — its own
    // f64 world position + quaternion, same chunked voxel payload.
    let ship_id = scene.add_grid(GridTransform {
        origin: DVec3::new(300.0, -80.0, -40.0),
        rotation: DQuat::from_rotation_z(0.5),
        voxel_world_size: 1.0,
    });
    // Object grids should not paint their own (grid-local, rotating)
    // sky — leave the sky to the world grid.
    scene.grid_mut(ship_id).expect("just added").render_sky = false;
    // ANCHOR_END: scene_grids

    // ANCHOR: edits
    let ground = scene.grid_mut(ground_id).expect("just added");
    // Solid slab: grid-local voxel coords, inclusive on both ends,
    // decomposed across as many chunks as it spans (here 4×4).
    ground.set_rect(
        IVec3::new(-200, -200, 200),
        IVec3::new(199, 199, 254),
        Some(GRASS),
    );
    // `Some(colour)` inserts, `None` carves back to air.
    ground.set_sphere(IVec3::new(0, 0, 195), 12, Some(STONE));
    ground.set_rect(IVec3::new(-3, -200, 190), IVec3::new(3, 199, 196), None);
    // ANCHOR_END: edits

    // ANCHOR: queries
    // Solid tests: inside the slab, then inside the carved tunnel.
    assert!(ground.voxel_solid(IVec3::new(0, 0, 210)));
    assert!(!ground.voxel_solid(IVec3::new(0, 100, 193)));
    // Colour queries answer on surface voxels; deep interior cells
    // are untextured in the slab format and read as `None`.
    assert_eq!(ground.voxel_color(IVec3::new(50, 50, 200)), Some(GRASS));
    // ANCHOR_END: queries

    // ANCHOR: recolour
    // GOTCHA: inserting over already-solid voxels does NOT repaint
    // them — span insertion only fills air. Recolour = carve, then
    // insert.
    let (lo, hi) = (IVec3::new(20, 20, 200), IVec3::new(24, 24, 204));
    ground.set_rect(lo, hi, Some(RED));
    assert_eq!(ground.voxel_color(IVec3::new(22, 22, 200)), Some(GRASS)); // unchanged!
    ground.set_rect(lo, hi, None); // carve…
    ground.set_rect(lo, hi, Some(RED)); // …then insert
    assert_eq!(ground.voxel_color(IVec3::new(22, 22, 200)), Some(RED));
    // ANCHOR_END: recolour

    // ANCHOR: colfunc
    // A carve exposes fresh interior walls; the plain edits paint
    // them colour 0 (black). The `_with_colfunc` variants ask a
    // closure instead — it sees grid-local coordinates, so gradients
    // stay continuous across chunk seams. Here: a crater whose walls
    // darken with depth.
    ground.set_sphere_with_colfunc(IVec3::new(60, 60, 200), 8, SpanOp::Carve, |_x, _y, z| {
        let depth = (z - 192).clamp(0, 15) as u8;
        VoxColor::rgb(0x6b, 0x40 + depth * 3, 0x2f)
    });
    // ANCHOR_END: colfunc

    // ANCHOR: snapshot
    // Name grids before saving: ids survive the round-trip, but the
    // generator / store hooks are host code and cannot be serialised
    // — the name is your key for rebinding them after a load.
    scene.grid_mut(ground_id).expect("ground exists").name = Some("ground".into());
    let bytes = scene.save_snapshot(); // versioned envelope
    let restored = Scene::load_snapshot(&bytes).expect("self-authored snapshot");
    assert_eq!(restored.grid_count(), 2);
    let (_, ground2) = restored
        .grids()
        .find(|(_, g)| g.name.as_deref() == Some("ground"))
        .expect("rebind by name");
    assert_eq!(ground2.voxel_color(IVec3::new(22, 22, 200)), Some(RED));
    // ANCHOR_END: snapshot

    // ANCHOR: streaming
    // Streaming: attach a generator + radii to a grid, then pump once
    // per frame with the camera's world position. Chunks within
    // `r_active` stream in; chunks beyond `r_evict` drop out; the band
    // between is hysteresis so a camera hovering on a boundary
    // doesn't thrash.
    let stream_id = scene.add_grid(GridTransform::at(DVec3::new(0.0, 4096.0, 0.0)));
    let store = Arc::new(MemoryStore::default());
    let grid = scene.grid_mut(stream_id).expect("just added");
    grid.set_generator(Some(Arc::new(FloorGenerator)));
    grid.set_chunk_store(Some(store));
    grid.stream_radius = StreamRadius::new(256.0, 384.0);

    let camera_near = DVec3::new(0.0, 4096.0, 100.0);
    scene.pump_streaming_sync(camera_near); // real games: `pump_streaming`
    let grid = scene.grid(stream_id).expect("still there");
    assert!(grid.chunk_count() > 0); // floor streamed in around the camera
    assert!(grid.voxel_solid(IVec3::new(5, 5, 240)));
    // ANCHOR_END: streaming

    // ANCHOR: streaming_edit
    // Edit the streamed floor, walk far away, come back. The active
    // set follows the camera: the old region evicts (edited chunks
    // are handed to the ChunkStore first) while a fresh set streams
    // in around the new position. On return the store wins over the
    // generator, so the edit survives; without a store, eviction
    // would silently revert the chunk to generator output.
    scene
        .grid_mut(stream_id)
        .expect("still there")
        .set_voxel(IVec3::new(5, 5, 240), None); // dig a hole
    scene.pump_streaming_sync(camera_near + DVec3::new(0.0, 100_000.0, 0.0));
    let grid = scene.grid(stream_id).expect("still there");
    assert!(grid.chunk(IVec3::ZERO).is_none()); // home chunk evicted…
    assert!(grid.chunk_count() > 0); // …but the far region streamed in
    scene.pump_streaming_sync(camera_near);
    let grid = scene.grid(stream_id).expect("re-streamed");
    // The hole survived evict + re-stream.
    assert!(!grid.voxel_solid(IVec3::new(5, 5, 240)));
    // ANCHOR_END: streaming_edit

    // ANCHOR: grid_scale
    // Per-grid scale: `voxel_world_size` is world units per voxel. A grid
    // built with `at_scale(origin, 2.0)` has voxels twice world size — a
    // coarse "planet" — while `0.25` gives a fine detail grid; both coexist
    // at their true relative sizes. Only the world↔grid boundary scales:
    // edits + queries stay in voxels, unchanged.
    let mut scaled = Scene::new();
    let planet = scaled.add_grid(GridTransform::at_scale(DVec3::ZERO, 2.0));
    scaled
        .grid_mut(planet)
        .expect("just added")
        // Same voxel edit API — grid-local coordinates.
        .set_voxel(IVec3::new(5, 5, 10), Some(STONE));
    // Grid-local voxel z=10 sits at WORLD z = 20 (10 voxels × 2.0). A world
    // raycast down that column reports the grid-local voxel it hit AND a
    // WORLD-space `t` — so hits across grids of different scale compare
    // correctly (the raycaster marches voxels but returns world distance).
    let hit = scaled
        .raycast(DVec3::new(11.0, 11.0, 0.0), DVec3::new(0.0, 0.0, 1.0), 64.0)
        .expect("ray hits the scaled voxel");
    assert_eq!(hit.voxel, IVec3::new(5, 5, 10)); // grid-local, unscaled
    assert!((hit.t - 20.0).abs() < 1e-4); // WORLD distance: 10 voxels × 2.0
                                          // ANCHOR_END: grid_scale

    println!("book_scene_graph: all scene-graph assertions hold");
}

pub fn remove_grid(&mut self, id: GridId) -> Option<Grid>

Remove a grid by id. Returns the removed Grid (so the caller can reclaim its chunks) or None if the id wasn’t registered. Removed ids are not reissued.

pub fn grid(&self, id: GridId) -> Option<&Grid>

Borrow a registered grid.

Examples found in repository

examples/book_scene_graph.rs (line 177)

fn main() {
    // ANCHOR: scene_grids
    let mut scene = Scene::new();
    // A static "world" grid at the origin…
    let ground_id = scene.add_grid(GridTransform::at(DVec3::ZERO));
    // …and a second grid placed and rotated independently — its own
    // f64 world position + quaternion, same chunked voxel payload.
    let ship_id = scene.add_grid(GridTransform {
        origin: DVec3::new(300.0, -80.0, -40.0),
        rotation: DQuat::from_rotation_z(0.5),
        voxel_world_size: 1.0,
    });
    // Object grids should not paint their own (grid-local, rotating)
    // sky — leave the sky to the world grid.
    scene.grid_mut(ship_id).expect("just added").render_sky = false;
    // ANCHOR_END: scene_grids

    // ANCHOR: edits
    let ground = scene.grid_mut(ground_id).expect("just added");
    // Solid slab: grid-local voxel coords, inclusive on both ends,
    // decomposed across as many chunks as it spans (here 4×4).
    ground.set_rect(
        IVec3::new(-200, -200, 200),
        IVec3::new(199, 199, 254),
        Some(GRASS),
    );
    // `Some(colour)` inserts, `None` carves back to air.
    ground.set_sphere(IVec3::new(0, 0, 195), 12, Some(STONE));
    ground.set_rect(IVec3::new(-3, -200, 190), IVec3::new(3, 199, 196), None);
    // ANCHOR_END: edits

    // ANCHOR: queries
    // Solid tests: inside the slab, then inside the carved tunnel.
    assert!(ground.voxel_solid(IVec3::new(0, 0, 210)));
    assert!(!ground.voxel_solid(IVec3::new(0, 100, 193)));
    // Colour queries answer on surface voxels; deep interior cells
    // are untextured in the slab format and read as `None`.
    assert_eq!(ground.voxel_color(IVec3::new(50, 50, 200)), Some(GRASS));
    // ANCHOR_END: queries

    // ANCHOR: recolour
    // GOTCHA: inserting over already-solid voxels does NOT repaint
    // them — span insertion only fills air. Recolour = carve, then
    // insert.
    let (lo, hi) = (IVec3::new(20, 20, 200), IVec3::new(24, 24, 204));
    ground.set_rect(lo, hi, Some(RED));
    assert_eq!(ground.voxel_color(IVec3::new(22, 22, 200)), Some(GRASS)); // unchanged!
    ground.set_rect(lo, hi, None); // carve…
    ground.set_rect(lo, hi, Some(RED)); // …then insert
    assert_eq!(ground.voxel_color(IVec3::new(22, 22, 200)), Some(RED));
    // ANCHOR_END: recolour

    // ANCHOR: colfunc
    // A carve exposes fresh interior walls; the plain edits paint
    // them colour 0 (black). The `_with_colfunc` variants ask a
    // closure instead — it sees grid-local coordinates, so gradients
    // stay continuous across chunk seams. Here: a crater whose walls
    // darken with depth.
    ground.set_sphere_with_colfunc(IVec3::new(60, 60, 200), 8, SpanOp::Carve, |_x, _y, z| {
        let depth = (z - 192).clamp(0, 15) as u8;
        VoxColor::rgb(0x6b, 0x40 + depth * 3, 0x2f)
    });
    // ANCHOR_END: colfunc

    // ANCHOR: snapshot
    // Name grids before saving: ids survive the round-trip, but the
    // generator / store hooks are host code and cannot be serialised
    // — the name is your key for rebinding them after a load.
    scene.grid_mut(ground_id).expect("ground exists").name = Some("ground".into());
    let bytes = scene.save_snapshot(); // versioned envelope
    let restored = Scene::load_snapshot(&bytes).expect("self-authored snapshot");
    assert_eq!(restored.grid_count(), 2);
    let (_, ground2) = restored
        .grids()
        .find(|(_, g)| g.name.as_deref() == Some("ground"))
        .expect("rebind by name");
    assert_eq!(ground2.voxel_color(IVec3::new(22, 22, 200)), Some(RED));
    // ANCHOR_END: snapshot

    // ANCHOR: streaming
    // Streaming: attach a generator + radii to a grid, then pump once
    // per frame with the camera's world position. Chunks within
    // `r_active` stream in; chunks beyond `r_evict` drop out; the band
    // between is hysteresis so a camera hovering on a boundary
    // doesn't thrash.
    let stream_id = scene.add_grid(GridTransform::at(DVec3::new(0.0, 4096.0, 0.0)));
    let store = Arc::new(MemoryStore::default());
    let grid = scene.grid_mut(stream_id).expect("just added");
    grid.set_generator(Some(Arc::new(FloorGenerator)));
    grid.set_chunk_store(Some(store));
    grid.stream_radius = StreamRadius::new(256.0, 384.0);

    let camera_near = DVec3::new(0.0, 4096.0, 100.0);
    scene.pump_streaming_sync(camera_near); // real games: `pump_streaming`
    let grid = scene.grid(stream_id).expect("still there");
    assert!(grid.chunk_count() > 0); // floor streamed in around the camera
    assert!(grid.voxel_solid(IVec3::new(5, 5, 240)));
    // ANCHOR_END: streaming

    // ANCHOR: streaming_edit
    // Edit the streamed floor, walk far away, come back. The active
    // set follows the camera: the old region evicts (edited chunks
    // are handed to the ChunkStore first) while a fresh set streams
    // in around the new position. On return the store wins over the
    // generator, so the edit survives; without a store, eviction
    // would silently revert the chunk to generator output.
    scene
        .grid_mut(stream_id)
        .expect("still there")
        .set_voxel(IVec3::new(5, 5, 240), None); // dig a hole
    scene.pump_streaming_sync(camera_near + DVec3::new(0.0, 100_000.0, 0.0));
    let grid = scene.grid(stream_id).expect("still there");
    assert!(grid.chunk(IVec3::ZERO).is_none()); // home chunk evicted…
    assert!(grid.chunk_count() > 0); // …but the far region streamed in
    scene.pump_streaming_sync(camera_near);
    let grid = scene.grid(stream_id).expect("re-streamed");
    // The hole survived evict + re-stream.
    assert!(!grid.voxel_solid(IVec3::new(5, 5, 240)));
    // ANCHOR_END: streaming_edit

    // ANCHOR: grid_scale
    // Per-grid scale: `voxel_world_size` is world units per voxel. A grid
    // built with `at_scale(origin, 2.0)` has voxels twice world size — a
    // coarse "planet" — while `0.25` gives a fine detail grid; both coexist
    // at their true relative sizes. Only the world↔grid boundary scales:
    // edits + queries stay in voxels, unchanged.
    let mut scaled = Scene::new();
    let planet = scaled.add_grid(GridTransform::at_scale(DVec3::ZERO, 2.0));
    scaled
        .grid_mut(planet)
        .expect("just added")
        // Same voxel edit API — grid-local coordinates.
        .set_voxel(IVec3::new(5, 5, 10), Some(STONE));
    // Grid-local voxel z=10 sits at WORLD z = 20 (10 voxels × 2.0). A world
    // raycast down that column reports the grid-local voxel it hit AND a
    // WORLD-space `t` — so hits across grids of different scale compare
    // correctly (the raycaster marches voxels but returns world distance).
    let hit = scaled
        .raycast(DVec3::new(11.0, 11.0, 0.0), DVec3::new(0.0, 0.0, 1.0), 64.0)
        .expect("ray hits the scaled voxel");
    assert_eq!(hit.voxel, IVec3::new(5, 5, 10)); // grid-local, unscaled
    assert!((hit.t - 20.0).abs() < 1e-4); // WORLD distance: 10 voxels × 2.0
                                          // ANCHOR_END: grid_scale

    println!("book_scene_graph: all scene-graph assertions hold");
}

pub fn grid_mut(&mut self, id: GridId) -> Option<&mut Grid>

Mutably borrow a registered grid.

Examples found in repository

examples/book_controller.rs (line 32)

fn build_world() -> Scene {
    let mut scene = Scene::new();
    let id = scene.add_grid(GridTransform::identity());
    let g = scene.grid_mut(id).expect("grid");
    // Ground slab: surface plane at z = 100 (+z is down, so the
    // slab fills downward).
    g.set_rect(
        IVec3::new(20, 20, 100),
        IVec3::new(140, 140, 120),
        Some(VoxColor::rgb(0x4d, 0x8a, 0x3a)),
    );
    // A 1-voxel ledge to step onto, and a wall to slide along.
    g.set_rect(
        IVec3::new(90, 20, 99),
        IVec3::new(140, 140, 99),
        Some(VoxColor::rgb(0x77, 0x66, 0x55)),
    );
    g.set_rect(
        IVec3::new(60, 70, 60),
        IVec3::new(62, 140, 99),
        Some(VoxColor::rgb(0x88, 0x44, 0x44)),
    );
    // A water curtain the veto lets the body wade through. Two
    // format facts (both pinned as engine tests): pass-through
    // geometry works up to 2 voxels thick — thicker walls grow a
    // colourless UnexposedSolid core no veto can classify — and
    // must sit ≥ 1 voxel inside the chunk (edge voxels lose their
    // side colours).
    g.set_rect(IVec3::new(40, 40, 80), IVec3::new(41, 60, 99), Some(WATER));
    scene
}

fn main() {
    let scene = build_world();

    // ANCHOR: setup
    // A walking body: a feet-positioned collision box, f64 world.
    // Distances are voxels, times seconds; +z is DOWN, so gravity is
    // positive and a jump impulse negative.
    let mut body = CharacterBody::new(CharacterDef {
        radius: 0.4,      // xy half-extent of the box
        height: 1.8,      // feet → head (toward -z)
        eye_height: 1.62, // feet → camera anchor
        step_up: 1.05,    // auto-step ledges up to 1 voxel
        solidity: Solidity {
            bedrock_blocks: false, // match your renderer's policy
            passable: Some(water_passes),
        },
        ..CharacterDef::default()
    });
    body.teleport(DVec3::new(50.0, 50.0, 95.0)); // FEET position
                                                 // ANCHOR_END: setup

    // ANCHOR: frame
    // Per frame: build a wish direction from input (unit-length or
    // zero — walk() clamps), call walk() EVERY frame (a zero wish is
    // what stops the body), then anchor the camera at the eye.
    let dt = 1.0 / 60.0;
    for frame in 0..480 {
        let input = WalkInput {
            wish: DVec3::new(1.0, 0.2, 0.0), // toward the ledge
            jump: frame == 120,              // one hop on the way
            ..WalkInput::default()           // sink (WT.1) + future fields
        };
        body.walk(&scene, dt, input);
    }
    let eye = body.eye_pos(); // = Camera::from_yaw_pitch(eye.into(), yaw, pitch)
                              // ANCHOR_END: frame

    // The trajectory the walk above promises, pinned:
    assert!(body.on_ground(), "settled after the hop");
    // It fell to the floor plane, then stepped up the 1-voxel ledge
    // (surface z = 99) while walking +x.
    assert!(body.pos().x > 90.0, "reached the ledge region");
    assert!(
        (body.pos().z - 99.0).abs() < 0.01,
        "standing on the ledge, feet at {}",
        body.pos().z
    );
    assert!(eye.z < body.pos().z, "the eye is above the feet (-z is up)");

    // Fly mode is the demos' free camera: no gravity, full-3D wish,
    // instant start/stop, still sliding along walls.
    body.set_mode(MoveMode::Fly);
    body.walk(&scene, dt, WalkInput::default());
    assert_eq!(body.vel(), DVec3::ZERO, "fly idles in place");

    // The water curtain from `build_world` is passable: probe the
    // veto directly (the same query walk() uses).
    let wading = roxlap_scene::box_overlaps_solid(
        &scene,
        DVec3::new(40.2, 50.0, 90.0),
        DVec3::new(40.8, 50.6, 91.8),
        body.def().solidity,
    );
    assert!(!wading, "water is passable under the veto");

    swim_demo();

    println!("book_controller: all controller assertions hold");
}

/// WT — the water + swimming section's snippets: a deep pool the body
/// falls into, floats in, dives through and breaches out of.
fn swim_demo() {
    // ANCHOR: water
    // Physics water is a WaterVolume on the grid — a grid-local voxel
    // AABB whose TOP face (min z — +z is down) is the surface. It is
    // independent of the voxels: fill the same region with a
    // volumetric-material shell for the visuals, or don't.
    let mut scene = Scene::new();
    let id = scene.add_grid(GridTransform::identity());
    let g = scene.grid_mut(id).expect("grid");
    // Basin floor, then 20 voxels of water above it (surface z = 100).
    g.set_rect(
        IVec3::new(20, 20, 120),
        IVec3::new(140, 140, 130),
        Some(VoxColor::rgb(0x50, 0x90, 0x50)),
    );
    g.add_water_volume(IVec3::new(20, 20, 100), IVec3::new(140, 140, 119));

    // A Walk-mode body dropped in swims AUTOMATICALLY once submerged
    // past `swim_enter_frac` of its height: buoyancy floats it to a
    // bob at the surface, `jump` strokes up, `sink` strokes down, and
    // a jump with the head above water breaches.
    let mut body = CharacterBody::new(CharacterDef::default());
    body.teleport(DVec3::new(80.0, 80.0, 115.0)); // deep in the pool
    for _ in 0..600 {
        body.walk(&scene, 1.0 / 60.0, WalkInput::default());
    }
    assert!(body.is_swimming(), "floated to the surface bob");
    assert!(!body.eye_in_water(&scene), "bobbing: the camera is dry");

    // Dive: hold `sink`. The submerged EYE is the hook for the
    // underwater feel — drive the WT.2 frame tint and the WT.3
    // listener lowpass from this one flag.
    for _ in 0..90 {
        body.walk(
            &scene,
            1.0 / 60.0,
            WalkInput {
                sink: true,
                ..WalkInput::default()
            },
        );
    }
    assert!(body.eye_in_water(&scene), "diving: tint + muffle now");
    // ANCHOR_END: water
}

examples/book_scene_graph.rs (line 97)

fn main() {
    // ANCHOR: scene_grids
    let mut scene = Scene::new();
    // A static "world" grid at the origin…
    let ground_id = scene.add_grid(GridTransform::at(DVec3::ZERO));
    // …and a second grid placed and rotated independently — its own
    // f64 world position + quaternion, same chunked voxel payload.
    let ship_id = scene.add_grid(GridTransform {
        origin: DVec3::new(300.0, -80.0, -40.0),
        rotation: DQuat::from_rotation_z(0.5),
        voxel_world_size: 1.0,
    });
    // Object grids should not paint their own (grid-local, rotating)
    // sky — leave the sky to the world grid.
    scene.grid_mut(ship_id).expect("just added").render_sky = false;
    // ANCHOR_END: scene_grids

    // ANCHOR: edits
    let ground = scene.grid_mut(ground_id).expect("just added");
    // Solid slab: grid-local voxel coords, inclusive on both ends,
    // decomposed across as many chunks as it spans (here 4×4).
    ground.set_rect(
        IVec3::new(-200, -200, 200),
        IVec3::new(199, 199, 254),
        Some(GRASS),
    );
    // `Some(colour)` inserts, `None` carves back to air.
    ground.set_sphere(IVec3::new(0, 0, 195), 12, Some(STONE));
    ground.set_rect(IVec3::new(-3, -200, 190), IVec3::new(3, 199, 196), None);
    // ANCHOR_END: edits

    // ANCHOR: queries
    // Solid tests: inside the slab, then inside the carved tunnel.
    assert!(ground.voxel_solid(IVec3::new(0, 0, 210)));
    assert!(!ground.voxel_solid(IVec3::new(0, 100, 193)));
    // Colour queries answer on surface voxels; deep interior cells
    // are untextured in the slab format and read as `None`.
    assert_eq!(ground.voxel_color(IVec3::new(50, 50, 200)), Some(GRASS));
    // ANCHOR_END: queries

    // ANCHOR: recolour
    // GOTCHA: inserting over already-solid voxels does NOT repaint
    // them — span insertion only fills air. Recolour = carve, then
    // insert.
    let (lo, hi) = (IVec3::new(20, 20, 200), IVec3::new(24, 24, 204));
    ground.set_rect(lo, hi, Some(RED));
    assert_eq!(ground.voxel_color(IVec3::new(22, 22, 200)), Some(GRASS)); // unchanged!
    ground.set_rect(lo, hi, None); // carve…
    ground.set_rect(lo, hi, Some(RED)); // …then insert
    assert_eq!(ground.voxel_color(IVec3::new(22, 22, 200)), Some(RED));
    // ANCHOR_END: recolour

    // ANCHOR: colfunc
    // A carve exposes fresh interior walls; the plain edits paint
    // them colour 0 (black). The `_with_colfunc` variants ask a
    // closure instead — it sees grid-local coordinates, so gradients
    // stay continuous across chunk seams. Here: a crater whose walls
    // darken with depth.
    ground.set_sphere_with_colfunc(IVec3::new(60, 60, 200), 8, SpanOp::Carve, |_x, _y, z| {
        let depth = (z - 192).clamp(0, 15) as u8;
        VoxColor::rgb(0x6b, 0x40 + depth * 3, 0x2f)
    });
    // ANCHOR_END: colfunc

    // ANCHOR: snapshot
    // Name grids before saving: ids survive the round-trip, but the
    // generator / store hooks are host code and cannot be serialised
    // — the name is your key for rebinding them after a load.
    scene.grid_mut(ground_id).expect("ground exists").name = Some("ground".into());
    let bytes = scene.save_snapshot(); // versioned envelope
    let restored = Scene::load_snapshot(&bytes).expect("self-authored snapshot");
    assert_eq!(restored.grid_count(), 2);
    let (_, ground2) = restored
        .grids()
        .find(|(_, g)| g.name.as_deref() == Some("ground"))
        .expect("rebind by name");
    assert_eq!(ground2.voxel_color(IVec3::new(22, 22, 200)), Some(RED));
    // ANCHOR_END: snapshot

    // ANCHOR: streaming
    // Streaming: attach a generator + radii to a grid, then pump once
    // per frame with the camera's world position. Chunks within
    // `r_active` stream in; chunks beyond `r_evict` drop out; the band
    // between is hysteresis so a camera hovering on a boundary
    // doesn't thrash.
    let stream_id = scene.add_grid(GridTransform::at(DVec3::new(0.0, 4096.0, 0.0)));
    let store = Arc::new(MemoryStore::default());
    let grid = scene.grid_mut(stream_id).expect("just added");
    grid.set_generator(Some(Arc::new(FloorGenerator)));
    grid.set_chunk_store(Some(store));
    grid.stream_radius = StreamRadius::new(256.0, 384.0);

    let camera_near = DVec3::new(0.0, 4096.0, 100.0);
    scene.pump_streaming_sync(camera_near); // real games: `pump_streaming`
    let grid = scene.grid(stream_id).expect("still there");
    assert!(grid.chunk_count() > 0); // floor streamed in around the camera
    assert!(grid.voxel_solid(IVec3::new(5, 5, 240)));
    // ANCHOR_END: streaming

    // ANCHOR: streaming_edit
    // Edit the streamed floor, walk far away, come back. The active
    // set follows the camera: the old region evicts (edited chunks
    // are handed to the ChunkStore first) while a fresh set streams
    // in around the new position. On return the store wins over the
    // generator, so the edit survives; without a store, eviction
    // would silently revert the chunk to generator output.
    scene
        .grid_mut(stream_id)
        .expect("still there")
        .set_voxel(IVec3::new(5, 5, 240), None); // dig a hole
    scene.pump_streaming_sync(camera_near + DVec3::new(0.0, 100_000.0, 0.0));
    let grid = scene.grid(stream_id).expect("still there");
    assert!(grid.chunk(IVec3::ZERO).is_none()); // home chunk evicted…
    assert!(grid.chunk_count() > 0); // …but the far region streamed in
    scene.pump_streaming_sync(camera_near);
    let grid = scene.grid(stream_id).expect("re-streamed");
    // The hole survived evict + re-stream.
    assert!(!grid.voxel_solid(IVec3::new(5, 5, 240)));
    // ANCHOR_END: streaming_edit

    // ANCHOR: grid_scale
    // Per-grid scale: `voxel_world_size` is world units per voxel. A grid
    // built with `at_scale(origin, 2.0)` has voxels twice world size — a
    // coarse "planet" — while `0.25` gives a fine detail grid; both coexist
    // at their true relative sizes. Only the world↔grid boundary scales:
    // edits + queries stay in voxels, unchanged.
    let mut scaled = Scene::new();
    let planet = scaled.add_grid(GridTransform::at_scale(DVec3::ZERO, 2.0));
    scaled
        .grid_mut(planet)
        .expect("just added")
        // Same voxel edit API — grid-local coordinates.
        .set_voxel(IVec3::new(5, 5, 10), Some(STONE));
    // Grid-local voxel z=10 sits at WORLD z = 20 (10 voxels × 2.0). A world
    // raycast down that column reports the grid-local voxel it hit AND a
    // WORLD-space `t` — so hits across grids of different scale compare
    // correctly (the raycaster marches voxels but returns world distance).
    let hit = scaled
        .raycast(DVec3::new(11.0, 11.0, 0.0), DVec3::new(0.0, 0.0, 1.0), 64.0)
        .expect("ray hits the scaled voxel");
    assert_eq!(hit.voxel, IVec3::new(5, 5, 10)); // grid-local, unscaled
    assert!((hit.t - 20.0).abs() < 1e-4); // WORLD distance: 10 voxels × 2.0
                                          // ANCHOR_END: grid_scale

    println!("book_scene_graph: all scene-graph assertions hold");
}

pub fn grids(&self) -> impl Iterator<Item = (GridId, &Grid)>

Iterator over all (id, grid) pairs in registration order is not guaranteed — the underlying map is a HashMap. Callers that need a stable order must sort by GridId.

Examples found in repository

examples/book_scene_graph.rs (line 156)

fn main() {
    // ANCHOR: scene_grids
    let mut scene = Scene::new();
    // A static "world" grid at the origin…
    let ground_id = scene.add_grid(GridTransform::at(DVec3::ZERO));
    // …and a second grid placed and rotated independently — its own
    // f64 world position + quaternion, same chunked voxel payload.
    let ship_id = scene.add_grid(GridTransform {
        origin: DVec3::new(300.0, -80.0, -40.0),
        rotation: DQuat::from_rotation_z(0.5),
        voxel_world_size: 1.0,
    });
    // Object grids should not paint their own (grid-local, rotating)
    // sky — leave the sky to the world grid.
    scene.grid_mut(ship_id).expect("just added").render_sky = false;
    // ANCHOR_END: scene_grids

    // ANCHOR: edits
    let ground = scene.grid_mut(ground_id).expect("just added");
    // Solid slab: grid-local voxel coords, inclusive on both ends,
    // decomposed across as many chunks as it spans (here 4×4).
    ground.set_rect(
        IVec3::new(-200, -200, 200),
        IVec3::new(199, 199, 254),
        Some(GRASS),
    );
    // `Some(colour)` inserts, `None` carves back to air.
    ground.set_sphere(IVec3::new(0, 0, 195), 12, Some(STONE));
    ground.set_rect(IVec3::new(-3, -200, 190), IVec3::new(3, 199, 196), None);
    // ANCHOR_END: edits

    // ANCHOR: queries
    // Solid tests: inside the slab, then inside the carved tunnel.
    assert!(ground.voxel_solid(IVec3::new(0, 0, 210)));
    assert!(!ground.voxel_solid(IVec3::new(0, 100, 193)));
    // Colour queries answer on surface voxels; deep interior cells
    // are untextured in the slab format and read as `None`.
    assert_eq!(ground.voxel_color(IVec3::new(50, 50, 200)), Some(GRASS));
    // ANCHOR_END: queries

    // ANCHOR: recolour
    // GOTCHA: inserting over already-solid voxels does NOT repaint
    // them — span insertion only fills air. Recolour = carve, then
    // insert.
    let (lo, hi) = (IVec3::new(20, 20, 200), IVec3::new(24, 24, 204));
    ground.set_rect(lo, hi, Some(RED));
    assert_eq!(ground.voxel_color(IVec3::new(22, 22, 200)), Some(GRASS)); // unchanged!
    ground.set_rect(lo, hi, None); // carve…
    ground.set_rect(lo, hi, Some(RED)); // …then insert
    assert_eq!(ground.voxel_color(IVec3::new(22, 22, 200)), Some(RED));
    // ANCHOR_END: recolour

    // ANCHOR: colfunc
    // A carve exposes fresh interior walls; the plain edits paint
    // them colour 0 (black). The `_with_colfunc` variants ask a
    // closure instead — it sees grid-local coordinates, so gradients
    // stay continuous across chunk seams. Here: a crater whose walls
    // darken with depth.
    ground.set_sphere_with_colfunc(IVec3::new(60, 60, 200), 8, SpanOp::Carve, |_x, _y, z| {
        let depth = (z - 192).clamp(0, 15) as u8;
        VoxColor::rgb(0x6b, 0x40 + depth * 3, 0x2f)
    });
    // ANCHOR_END: colfunc

    // ANCHOR: snapshot
    // Name grids before saving: ids survive the round-trip, but the
    // generator / store hooks are host code and cannot be serialised
    // — the name is your key for rebinding them after a load.
    scene.grid_mut(ground_id).expect("ground exists").name = Some("ground".into());
    let bytes = scene.save_snapshot(); // versioned envelope
    let restored = Scene::load_snapshot(&bytes).expect("self-authored snapshot");
    assert_eq!(restored.grid_count(), 2);
    let (_, ground2) = restored
        .grids()
        .find(|(_, g)| g.name.as_deref() == Some("ground"))
        .expect("rebind by name");
    assert_eq!(ground2.voxel_color(IVec3::new(22, 22, 200)), Some(RED));
    // ANCHOR_END: snapshot

    // ANCHOR: streaming
    // Streaming: attach a generator + radii to a grid, then pump once
    // per frame with the camera's world position. Chunks within
    // `r_active` stream in; chunks beyond `r_evict` drop out; the band
    // between is hysteresis so a camera hovering on a boundary
    // doesn't thrash.
    let stream_id = scene.add_grid(GridTransform::at(DVec3::new(0.0, 4096.0, 0.0)));
    let store = Arc::new(MemoryStore::default());
    let grid = scene.grid_mut(stream_id).expect("just added");
    grid.set_generator(Some(Arc::new(FloorGenerator)));
    grid.set_chunk_store(Some(store));
    grid.stream_radius = StreamRadius::new(256.0, 384.0);

    let camera_near = DVec3::new(0.0, 4096.0, 100.0);
    scene.pump_streaming_sync(camera_near); // real games: `pump_streaming`
    let grid = scene.grid(stream_id).expect("still there");
    assert!(grid.chunk_count() > 0); // floor streamed in around the camera
    assert!(grid.voxel_solid(IVec3::new(5, 5, 240)));
    // ANCHOR_END: streaming

    // ANCHOR: streaming_edit
    // Edit the streamed floor, walk far away, come back. The active
    // set follows the camera: the old region evicts (edited chunks
    // are handed to the ChunkStore first) while a fresh set streams
    // in around the new position. On return the store wins over the
    // generator, so the edit survives; without a store, eviction
    // would silently revert the chunk to generator output.
    scene
        .grid_mut(stream_id)
        .expect("still there")
        .set_voxel(IVec3::new(5, 5, 240), None); // dig a hole
    scene.pump_streaming_sync(camera_near + DVec3::new(0.0, 100_000.0, 0.0));
    let grid = scene.grid(stream_id).expect("still there");
    assert!(grid.chunk(IVec3::ZERO).is_none()); // home chunk evicted…
    assert!(grid.chunk_count() > 0); // …but the far region streamed in
    scene.pump_streaming_sync(camera_near);
    let grid = scene.grid(stream_id).expect("re-streamed");
    // The hole survived evict + re-stream.
    assert!(!grid.voxel_solid(IVec3::new(5, 5, 240)));
    // ANCHOR_END: streaming_edit

    // ANCHOR: grid_scale
    // Per-grid scale: `voxel_world_size` is world units per voxel. A grid
    // built with `at_scale(origin, 2.0)` has voxels twice world size — a
    // coarse "planet" — while `0.25` gives a fine detail grid; both coexist
    // at their true relative sizes. Only the world↔grid boundary scales:
    // edits + queries stay in voxels, unchanged.
    let mut scaled = Scene::new();
    let planet = scaled.add_grid(GridTransform::at_scale(DVec3::ZERO, 2.0));
    scaled
        .grid_mut(planet)
        .expect("just added")
        // Same voxel edit API — grid-local coordinates.
        .set_voxel(IVec3::new(5, 5, 10), Some(STONE));
    // Grid-local voxel z=10 sits at WORLD z = 20 (10 voxels × 2.0). A world
    // raycast down that column reports the grid-local voxel it hit AND a
    // WORLD-space `t` — so hits across grids of different scale compare
    // correctly (the raycaster marches voxels but returns world distance).
    let hit = scaled
        .raycast(DVec3::new(11.0, 11.0, 0.0), DVec3::new(0.0, 0.0, 1.0), 64.0)
        .expect("ray hits the scaled voxel");
    assert_eq!(hit.voxel, IVec3::new(5, 5, 10)); // grid-local, unscaled
    assert!((hit.t - 20.0).abs() < 1e-4); // WORLD distance: 10 voxels × 2.0
                                          // ANCHOR_END: grid_scale

    println!("book_scene_graph: all scene-graph assertions hold");
}

pub fn grids_mut(&mut self) -> impl Iterator<Item = (GridId, &mut Grid)>

Mutable iterator over all (id, grid) pairs. Yield order is not guaranteed (HashMap-backed).

pub fn resolve_voxel( &self, world: DVec3, ray_dir: DVec3, ) -> Option<(GridId, IVec3)>

Resolve a world-space surface hit to the owning grid + its grid-local voxel — the picking back half. ray_dir is the view direction the hit was found along (need not be normalised); the point is nudged half a voxel along it, past the surface and into the solid cell, before each grid’s Grid::voxel_solid test. Returns the first grid that is solid there (transform-correct for rotated/translated grids), or None if none claims it.

Backend-agnostic: pair with a renderer depth read to turn a click into a voxel — world = cam.pos + t · normalize(ray_dir), then resolve_voxel(world, ray_dir). roxlap-render’s SceneRenderer::pick wires exactly that.

pub fn raycast( &self, origin: DVec3, dir: DVec3, max_dist: f64, ) -> Option<RayHit>

Cast a world-space ray and return the nearest solid voxel hit across all grids, or None if nothing solid lies within max_dist. Renderer-independent (no depth buffer, no camera) — the primitive for line-of-sight, projectiles, AI probing, and off-screen / backend-agnostic picking.

dir need not be normalised. Each grid’s ray is transformed into the grid’s local frame (so rotated / translated grids are handled exactly) and marched with a voxel DDA against Grid::voxel_solid; the closest hit by world distance t wins. The step budget is bounded by max_dist, so empty space is safe but not free — a chunk-level skip is a future optimisation if hot.

Examples found in repository

examples/book_scene_graph.rs (line 221)

fn main() {
    // ANCHOR: scene_grids
    let mut scene = Scene::new();
    // A static "world" grid at the origin…
    let ground_id = scene.add_grid(GridTransform::at(DVec3::ZERO));
    // …and a second grid placed and rotated independently — its own
    // f64 world position + quaternion, same chunked voxel payload.
    let ship_id = scene.add_grid(GridTransform {
        origin: DVec3::new(300.0, -80.0, -40.0),
        rotation: DQuat::from_rotation_z(0.5),
        voxel_world_size: 1.0,
    });
    // Object grids should not paint their own (grid-local, rotating)
    // sky — leave the sky to the world grid.
    scene.grid_mut(ship_id).expect("just added").render_sky = false;
    // ANCHOR_END: scene_grids

    // ANCHOR: edits
    let ground = scene.grid_mut(ground_id).expect("just added");
    // Solid slab: grid-local voxel coords, inclusive on both ends,
    // decomposed across as many chunks as it spans (here 4×4).
    ground.set_rect(
        IVec3::new(-200, -200, 200),
        IVec3::new(199, 199, 254),
        Some(GRASS),
    );
    // `Some(colour)` inserts, `None` carves back to air.
    ground.set_sphere(IVec3::new(0, 0, 195), 12, Some(STONE));
    ground.set_rect(IVec3::new(-3, -200, 190), IVec3::new(3, 199, 196), None);
    // ANCHOR_END: edits

    // ANCHOR: queries
    // Solid tests: inside the slab, then inside the carved tunnel.
    assert!(ground.voxel_solid(IVec3::new(0, 0, 210)));
    assert!(!ground.voxel_solid(IVec3::new(0, 100, 193)));
    // Colour queries answer on surface voxels; deep interior cells
    // are untextured in the slab format and read as `None`.
    assert_eq!(ground.voxel_color(IVec3::new(50, 50, 200)), Some(GRASS));
    // ANCHOR_END: queries

    // ANCHOR: recolour
    // GOTCHA: inserting over already-solid voxels does NOT repaint
    // them — span insertion only fills air. Recolour = carve, then
    // insert.
    let (lo, hi) = (IVec3::new(20, 20, 200), IVec3::new(24, 24, 204));
    ground.set_rect(lo, hi, Some(RED));
    assert_eq!(ground.voxel_color(IVec3::new(22, 22, 200)), Some(GRASS)); // unchanged!
    ground.set_rect(lo, hi, None); // carve…
    ground.set_rect(lo, hi, Some(RED)); // …then insert
    assert_eq!(ground.voxel_color(IVec3::new(22, 22, 200)), Some(RED));
    // ANCHOR_END: recolour

    // ANCHOR: colfunc
    // A carve exposes fresh interior walls; the plain edits paint
    // them colour 0 (black). The `_with_colfunc` variants ask a
    // closure instead — it sees grid-local coordinates, so gradients
    // stay continuous across chunk seams. Here: a crater whose walls
    // darken with depth.
    ground.set_sphere_with_colfunc(IVec3::new(60, 60, 200), 8, SpanOp::Carve, |_x, _y, z| {
        let depth = (z - 192).clamp(0, 15) as u8;
        VoxColor::rgb(0x6b, 0x40 + depth * 3, 0x2f)
    });
    // ANCHOR_END: colfunc

    // ANCHOR: snapshot
    // Name grids before saving: ids survive the round-trip, but the
    // generator / store hooks are host code and cannot be serialised
    // — the name is your key for rebinding them after a load.
    scene.grid_mut(ground_id).expect("ground exists").name = Some("ground".into());
    let bytes = scene.save_snapshot(); // versioned envelope
    let restored = Scene::load_snapshot(&bytes).expect("self-authored snapshot");
    assert_eq!(restored.grid_count(), 2);
    let (_, ground2) = restored
        .grids()
        .find(|(_, g)| g.name.as_deref() == Some("ground"))
        .expect("rebind by name");
    assert_eq!(ground2.voxel_color(IVec3::new(22, 22, 200)), Some(RED));
    // ANCHOR_END: snapshot

    // ANCHOR: streaming
    // Streaming: attach a generator + radii to a grid, then pump once
    // per frame with the camera's world position. Chunks within
    // `r_active` stream in; chunks beyond `r_evict` drop out; the band
    // between is hysteresis so a camera hovering on a boundary
    // doesn't thrash.
    let stream_id = scene.add_grid(GridTransform::at(DVec3::new(0.0, 4096.0, 0.0)));
    let store = Arc::new(MemoryStore::default());
    let grid = scene.grid_mut(stream_id).expect("just added");
    grid.set_generator(Some(Arc::new(FloorGenerator)));
    grid.set_chunk_store(Some(store));
    grid.stream_radius = StreamRadius::new(256.0, 384.0);

    let camera_near = DVec3::new(0.0, 4096.0, 100.0);
    scene.pump_streaming_sync(camera_near); // real games: `pump_streaming`
    let grid = scene.grid(stream_id).expect("still there");
    assert!(grid.chunk_count() > 0); // floor streamed in around the camera
    assert!(grid.voxel_solid(IVec3::new(5, 5, 240)));
    // ANCHOR_END: streaming

    // ANCHOR: streaming_edit
    // Edit the streamed floor, walk far away, come back. The active
    // set follows the camera: the old region evicts (edited chunks
    // are handed to the ChunkStore first) while a fresh set streams
    // in around the new position. On return the store wins over the
    // generator, so the edit survives; without a store, eviction
    // would silently revert the chunk to generator output.
    scene
        .grid_mut(stream_id)
        .expect("still there")
        .set_voxel(IVec3::new(5, 5, 240), None); // dig a hole
    scene.pump_streaming_sync(camera_near + DVec3::new(0.0, 100_000.0, 0.0));
    let grid = scene.grid(stream_id).expect("still there");
    assert!(grid.chunk(IVec3::ZERO).is_none()); // home chunk evicted…
    assert!(grid.chunk_count() > 0); // …but the far region streamed in
    scene.pump_streaming_sync(camera_near);
    let grid = scene.grid(stream_id).expect("re-streamed");
    // The hole survived evict + re-stream.
    assert!(!grid.voxel_solid(IVec3::new(5, 5, 240)));
    // ANCHOR_END: streaming_edit

    // ANCHOR: grid_scale
    // Per-grid scale: `voxel_world_size` is world units per voxel. A grid
    // built with `at_scale(origin, 2.0)` has voxels twice world size — a
    // coarse "planet" — while `0.25` gives a fine detail grid; both coexist
    // at their true relative sizes. Only the world↔grid boundary scales:
    // edits + queries stay in voxels, unchanged.
    let mut scaled = Scene::new();
    let planet = scaled.add_grid(GridTransform::at_scale(DVec3::ZERO, 2.0));
    scaled
        .grid_mut(planet)
        .expect("just added")
        // Same voxel edit API — grid-local coordinates.
        .set_voxel(IVec3::new(5, 5, 10), Some(STONE));
    // Grid-local voxel z=10 sits at WORLD z = 20 (10 voxels × 2.0). A world
    // raycast down that column reports the grid-local voxel it hit AND a
    // WORLD-space `t` — so hits across grids of different scale compare
    // correctly (the raycaster marches voxels but returns world distance).
    let hit = scaled
        .raycast(DVec3::new(11.0, 11.0, 0.0), DVec3::new(0.0, 0.0, 1.0), 64.0)
        .expect("ray hits the scaled voxel");
    assert_eq!(hit.voxel, IVec3::new(5, 5, 10)); // grid-local, unscaled
    assert!((hit.t - 20.0).abs() < 1e-4); // WORLD distance: 10 voxels × 2.0
                                          // ANCHOR_END: grid_scale

    println!("book_scene_graph: all scene-graph assertions hold");
}

pub fn set_streaming_threads(&mut self, n: usize)

Configure the number of worker threads in the dedicated streaming pool (S7.3).

Lazily applied — the pool itself is constructed on the first Self::pump_streaming call. If the pool was already built (i.e. a previous pump_streaming already dispatched at least one task), it gets dropped and rebuilt. Dropping the old pool blocks until all of its in-flight tasks finish (rayon’s contract); any results those tasks sent are still drained by the next pump_streaming because the channel survives the rebuild.

The streaming pool is separate from rayon’s global pool (which R12 multicore rendering uses), so chunk generation doesn’t compete with render threads. Sensible values are 1 to ~4 — generation work is CPU-bound but should leave most of the box for everything else.

On wasm32 this is a no-op (no rayon pool available); pump_streaming runs synchronously there.

Panics

Panics on native if n == 0 (zero-thread pools are not supported; the scene crate’s S7.1 helper already disallows the equivalent for StreamRadius::r_active < 0).

pub fn pump_streaming(&mut self, camera_world_pos: DVec3)

Asynchronous streaming pump (S7.3).

On native, dispatches missing-chunk generations onto a dedicated rayon pool, drains any results that arrived since the last pump, runs the eviction pass, and tracks in-flight tasks in each grid’s Grid::pending_gen set. The drain uses the per-chunk version counter from S7.2 to discard results whose chunk was edited mid-generation.

On wasm32 this short-circuits to Self::pump_streaming_sync — no thread pool is available there, but the same per-grid stream-in / evict semantics apply.

Call once per frame from the render thread. Cheap when nothing changed (early-exit on disabled grids, try_recv loops empty fast).

pub fn pump_streaming_sync(&mut self, camera_world_pos: DVec3)

Synchronous streaming pump (S7.1).

For each grid with a non-StreamRadius::DISABLED policy:

1. Project the world-space camera into grid-local coords (inverse rotation + origin subtract).
2. Stream in any chunk whose AABB-to-camera distance is <= r_active, calling Grid::ensure_chunk_generated. No-ops gracefully if the grid has no generator attached (so callers can use the eviction half of streaming on a purely-edited grid).
3. Evict any chunk whose AABB-to-camera distance exceeds r_evict from the grid’s chunk map. Eviction also clears the cached BillboardCache (the bounding sphere may shrink, invalidating impostor projections; the next Far-tier render rebuilds lazily).

Both passes use the f64 grid-local position so rotation + non-axis-aligned grids stream and evict correctly. The generate path is blocking — S7.3 will move it to a background rayon pool with pump_streaming (non-blocking). Callers that want the async variant in S7.0/S7.1 stages should keep r_active small.

Examples found in repository

examples/book_scene_graph.rs (line 176)

fn main() {
    // ANCHOR: scene_grids
    let mut scene = Scene::new();
    // A static "world" grid at the origin…
    let ground_id = scene.add_grid(GridTransform::at(DVec3::ZERO));
    // …and a second grid placed and rotated independently — its own
    // f64 world position + quaternion, same chunked voxel payload.
    let ship_id = scene.add_grid(GridTransform {
        origin: DVec3::new(300.0, -80.0, -40.0),
        rotation: DQuat::from_rotation_z(0.5),
        voxel_world_size: 1.0,
    });
    // Object grids should not paint their own (grid-local, rotating)
    // sky — leave the sky to the world grid.
    scene.grid_mut(ship_id).expect("just added").render_sky = false;
    // ANCHOR_END: scene_grids

    // ANCHOR: edits
    let ground = scene.grid_mut(ground_id).expect("just added");
    // Solid slab: grid-local voxel coords, inclusive on both ends,
    // decomposed across as many chunks as it spans (here 4×4).
    ground.set_rect(
        IVec3::new(-200, -200, 200),
        IVec3::new(199, 199, 254),
        Some(GRASS),
    );
    // `Some(colour)` inserts, `None` carves back to air.
    ground.set_sphere(IVec3::new(0, 0, 195), 12, Some(STONE));
    ground.set_rect(IVec3::new(-3, -200, 190), IVec3::new(3, 199, 196), None);
    // ANCHOR_END: edits

    // ANCHOR: queries
    // Solid tests: inside the slab, then inside the carved tunnel.
    assert!(ground.voxel_solid(IVec3::new(0, 0, 210)));
    assert!(!ground.voxel_solid(IVec3::new(0, 100, 193)));
    // Colour queries answer on surface voxels; deep interior cells
    // are untextured in the slab format and read as `None`.
    assert_eq!(ground.voxel_color(IVec3::new(50, 50, 200)), Some(GRASS));
    // ANCHOR_END: queries

    // ANCHOR: recolour
    // GOTCHA: inserting over already-solid voxels does NOT repaint
    // them — span insertion only fills air. Recolour = carve, then
    // insert.
    let (lo, hi) = (IVec3::new(20, 20, 200), IVec3::new(24, 24, 204));
    ground.set_rect(lo, hi, Some(RED));
    assert_eq!(ground.voxel_color(IVec3::new(22, 22, 200)), Some(GRASS)); // unchanged!
    ground.set_rect(lo, hi, None); // carve…
    ground.set_rect(lo, hi, Some(RED)); // …then insert
    assert_eq!(ground.voxel_color(IVec3::new(22, 22, 200)), Some(RED));
    // ANCHOR_END: recolour

    // ANCHOR: colfunc
    // A carve exposes fresh interior walls; the plain edits paint
    // them colour 0 (black). The `_with_colfunc` variants ask a
    // closure instead — it sees grid-local coordinates, so gradients
    // stay continuous across chunk seams. Here: a crater whose walls
    // darken with depth.
    ground.set_sphere_with_colfunc(IVec3::new(60, 60, 200), 8, SpanOp::Carve, |_x, _y, z| {
        let depth = (z - 192).clamp(0, 15) as u8;
        VoxColor::rgb(0x6b, 0x40 + depth * 3, 0x2f)
    });
    // ANCHOR_END: colfunc

    // ANCHOR: snapshot
    // Name grids before saving: ids survive the round-trip, but the
    // generator / store hooks are host code and cannot be serialised
    // — the name is your key for rebinding them after a load.
    scene.grid_mut(ground_id).expect("ground exists").name = Some("ground".into());
    let bytes = scene.save_snapshot(); // versioned envelope
    let restored = Scene::load_snapshot(&bytes).expect("self-authored snapshot");
    assert_eq!(restored.grid_count(), 2);
    let (_, ground2) = restored
        .grids()
        .find(|(_, g)| g.name.as_deref() == Some("ground"))
        .expect("rebind by name");
    assert_eq!(ground2.voxel_color(IVec3::new(22, 22, 200)), Some(RED));
    // ANCHOR_END: snapshot

    // ANCHOR: streaming
    // Streaming: attach a generator + radii to a grid, then pump once
    // per frame with the camera's world position. Chunks within
    // `r_active` stream in; chunks beyond `r_evict` drop out; the band
    // between is hysteresis so a camera hovering on a boundary
    // doesn't thrash.
    let stream_id = scene.add_grid(GridTransform::at(DVec3::new(0.0, 4096.0, 0.0)));
    let store = Arc::new(MemoryStore::default());
    let grid = scene.grid_mut(stream_id).expect("just added");
    grid.set_generator(Some(Arc::new(FloorGenerator)));
    grid.set_chunk_store(Some(store));
    grid.stream_radius = StreamRadius::new(256.0, 384.0);

    let camera_near = DVec3::new(0.0, 4096.0, 100.0);
    scene.pump_streaming_sync(camera_near); // real games: `pump_streaming`
    let grid = scene.grid(stream_id).expect("still there");
    assert!(grid.chunk_count() > 0); // floor streamed in around the camera
    assert!(grid.voxel_solid(IVec3::new(5, 5, 240)));
    // ANCHOR_END: streaming

    // ANCHOR: streaming_edit
    // Edit the streamed floor, walk far away, come back. The active
    // set follows the camera: the old region evicts (edited chunks
    // are handed to the ChunkStore first) while a fresh set streams
    // in around the new position. On return the store wins over the
    // generator, so the edit survives; without a store, eviction
    // would silently revert the chunk to generator output.
    scene
        .grid_mut(stream_id)
        .expect("still there")
        .set_voxel(IVec3::new(5, 5, 240), None); // dig a hole
    scene.pump_streaming_sync(camera_near + DVec3::new(0.0, 100_000.0, 0.0));
    let grid = scene.grid(stream_id).expect("still there");
    assert!(grid.chunk(IVec3::ZERO).is_none()); // home chunk evicted…
    assert!(grid.chunk_count() > 0); // …but the far region streamed in
    scene.pump_streaming_sync(camera_near);
    let grid = scene.grid(stream_id).expect("re-streamed");
    // The hole survived evict + re-stream.
    assert!(!grid.voxel_solid(IVec3::new(5, 5, 240)));
    // ANCHOR_END: streaming_edit

    // ANCHOR: grid_scale
    // Per-grid scale: `voxel_world_size` is world units per voxel. A grid
    // built with `at_scale(origin, 2.0)` has voxels twice world size — a
    // coarse "planet" — while `0.25` gives a fine detail grid; both coexist
    // at their true relative sizes. Only the world↔grid boundary scales:
    // edits + queries stay in voxels, unchanged.
    let mut scaled = Scene::new();
    let planet = scaled.add_grid(GridTransform::at_scale(DVec3::ZERO, 2.0));
    scaled
        .grid_mut(planet)
        .expect("just added")
        // Same voxel edit API — grid-local coordinates.
        .set_voxel(IVec3::new(5, 5, 10), Some(STONE));
    // Grid-local voxel z=10 sits at WORLD z = 20 (10 voxels × 2.0). A world
    // raycast down that column reports the grid-local voxel it hit AND a
    // WORLD-space `t` — so hits across grids of different scale compare
    // correctly (the raycaster marches voxels but returns world distance).
    let hit = scaled
        .raycast(DVec3::new(11.0, 11.0, 0.0), DVec3::new(0.0, 0.0, 1.0), 64.0)
        .expect("ray hits the scaled voxel");
    assert_eq!(hit.voxel, IVec3::new(5, 5, 10)); // grid-local, unscaled
    assert!((hit.t - 20.0).abs() < 1e-4); // WORLD distance: 10 voxels × 2.0
                                          // ANCHOR_END: grid_scale

    println!("book_scene_graph: all scene-graph assertions hold");
}

Trait Implementations

impl Debug for Scene

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Scene

fn default() -> Scene

Returns the “default value” for a type.