material_playground/

material-playground.rs

//! One scene, every knob live: `Sky` pairs a whole scene's sky with its
//! sun. `Dawn`, `Noon`, `Dusk` and `Night` each pair a gradient with a
//! sun of its own color and direction; six loaded images each pair with
//! a sun that fits it, from a bright sky's own bright sun to two space
//! images lit by none; `Default` is the engine's own grey sky and white
//! sun. The lamp and the spotlight add their own light beside it, and a
//! material and the post chain read from sliders too.
//!
//! Hold the right mouse button and drag to look around, `W`/`A`/`S`/`D`
//! to move along the view and to its side, `Space`/`Left Shift` up and
//! down, and the wheel to scale how far each move goes; the `eye` stays
//! above the ground plane wherever it moves.
//!
//! The ground draws the shading, relief and emissive map pairs, left
//! plain and right checked on or off, the front sphere whose material a
//! set of sliders resolves new each frame, a row where each sphere's own
//! roughness rises so what the sky reflects reads apart across it, a
//! cloth displaced by a wave and drawn from both its sides, and a
//! pulsing sphere beside three pillars a light can shadow. The controls
//! stay in a side area of fixed width, not the bare UI layer, so the
//! flat grey default sky does not read as a slab under a row that spans
//! the whole window.

use mirage_engine::prelude::*;

/// Ground plane's side length, in meters.
const GROUND_SIZE: f32 = 18.0;

/// A pair's two halves are drawn this far either side of its row's center,
/// in meters.
const PAIR_HALF_SPACING: f32 = 1.0;

/// Depth, along `z`, of each map pair.
const SHADING_Z: f32 = 3.4;
const RELIEF_Z: f32 = 1.8;
const EMISSIVE_Z: f32 = 0.2;

/// A sphere's radius, so its center is a radius above the ground.
const SPHERE_RADIUS: f32 = 0.5;
/// An emissive cube's edge length.
const CUBE_SIZE: f32 = 0.85;

/// The front sphere's position and scale, ahead of every pair and larger,
/// so its live material reads apart from them.
const FRONT_POSITION: Vec3 = Vec3::new(0.0, 0.7, -1.6);
const FRONT_SCALE: f32 = 1.4;

/// Sphere density every built sphere in this scene shares.
const SPHERE_SUBDIVISIONS: u32 = 3;

/// How many draws the reflection row makes, and the meters between their
/// centers.
const REFLECT_ROW_COUNT: usize = 5;
const REFLECT_ROW_SPACING: f32 = 1.5;
const REFLECT_ROW_Z: f32 = -1.6;
const REFLECT_ROW_RADIUS: f32 = 0.55;

const GROUND_COLOR: Color = Color::rgb(0.24, 0.25, 0.22);
const SHADING_TINT: Color = Color::rgb(0.55, 0.55, 0.6);
const RELIEF_TINT: Color = Color::rgb(0.5, 0.45, 0.35);
const EMISSIVE_BASE: Color = Color::rgb(0.04, 0.04, 0.05);
const EMISSIVE_GLOW: Color = Color::rgb(3.2, 2.2, 0.7);

/// Texel side length of every generated map: coarse enough that each
/// checker cell reads as a distinct part on a sphere or a cube face.
const MAP_SIZE: UVec2 = UVec2::new(64, 64);

/// Checker cell width, in texels, for the shading map.
const SHADING_CELL: u32 = 8;
/// The shading checker's two states: occlusion, roughness and metallic —
/// one square low across all three, the other full across all three.
const SHADING_LOW: [u8; 3] = [70, 40, 15];
const SHADING_HIGH: [u8; 3] = [255, 225, 235];

/// Checker cell width, in texels, for the emissive map.
const EMISSIVE_CELL: u32 = 6;

/// Wave count the relief's texture repeats across its map, and the peak
/// slope of its surface, in height over distance.
const BUMP_WAVES: f32 = 6.0;
const BUMP_SLOPE: f32 = 1.15;

/// `BannerCloth`'s width and height, in meters.
const BANNER_WIDTH: f32 = 1.1;
const BANNER_HEIGHT: f32 = 0.7;

/// Columns `BannerCloth` splits into, so its wave curves smoothly.
const BANNER_COLUMNS: u32 = 10;

/// Where the pillars, the pole, the cloth and the pulsing sphere are
/// placed, added to every one of their own positions: apart from the
/// pairs and the reflection row, so a light's shadow has clear ground to
/// land on.
const OUTPOST: Vec3 = Vec3::new(-4.6, 0.0, -0.8);

const PILLARS: [(Vec3, Vec3); 3] = [
    (Vec3::new(-1.8, 0.6, -0.6), Vec3::new(0.6, 1.2, 0.6)),
    (Vec3::new(0.4, 0.4, -1.6), Vec3::new(0.5, 0.8, 0.5)),
    (Vec3::new(1.7, 0.9, 0.4), Vec3::new(0.55, 1.8, 0.55)),
];

const POLE_POSITION: Vec3 = Vec3::new(-2.6, 1.0, 0.4);
const POLE_SCALE: Vec3 = Vec3::new(0.12, 2.0, 0.12);
const BANNER_MOUNT: Vec3 = Vec3::new(-2.54, 1.55, 0.46);

const FIELD_ORB_POSITION: Vec3 = Vec3::new(1.3, 1.1, 1.6);
const FIELD_ORB_SCALE: f32 = 0.7;

/// The lamp's fixed position and reach, in meters.
const LAMP_POSITION: Vec3 = Vec3::new(2.4, 1.4, -3.0);
const LAMP_RANGE: f32 = 5.0;

/// The spotlight's fixed placement: where it is placed, which way its
/// cone points, its reach in meters and its width in radians.
const SPOT_POSITION: Vec3 = Vec3::new(-3.4, 3.0, 1.6);
const SPOT_DIRECTION: Vec3 = Vec3::new(0.55, -1.0, -1.0);
const SPOT_RANGE: f32 = 7.0;
const SPOT_ANGLE: f32 = 0.5;

/// The camera's vertical field of view, in degrees.
const CAMERA_FOV: f32 = 46.0;
/// Where the camera starts, and the `yaw` and the pitch, in radians, it
/// starts turned to.
const START_EYE: Vec3 = Vec3::new(-0.6, 2.2, 9.0);
const START_YAW: f32 = 0.0;
const START_PITCH: f32 = -0.15;
/// How far short of straight up or down the pitch may turn, in radians,
/// where a turn alone reads as nothing.
const PITCH_LIMIT: f32 = 1.5;
/// The `eye`'s least height above the ground plane, in meters: held above
/// zero so a move can never take it below.
const MIN_EYE_HEIGHT: f32 = 0.3;
/// Radians the pointer's own motion turns the view by, per physical
/// pixel it crosses, before the axis it reads through bounds it: a drag
/// across the whole window turns about a quarter turn.
const LOOK_SENSITIVITY: f32 = core::f32::consts::FRAC_PI_2 / 1280.0;
/// Meters a move key covers per second, at [`Playground::speed_scale`]'s
/// own default.
const MOVE_SPEED: f32 = 4.0;
/// The factor one full wheel step multiplies the move speed apart from.
const SPEED_STEP: f32 = 1.5;
/// The move speed's own least and most, as a factor of [`MOVE_SPEED`].
const MIN_SPEED_SCALE: f32 = 0.2;
const MAX_SPEED_SCALE: f32 = 5.0;

/// Bloom this scene starts at, past the engine's own default: enough that
/// [`EMISSIVE_GLOW`] and the brightest lights scatter right away.
const START_BLOOM: f32 = 0.25;
const START_EXPOSURE: f32 = 1.0;

/// The sky a frame that keeps [`Sky::Default`] draws and is lit by: the
/// same flat grey the engine falls back to when a frame sets none.
const DEFAULT_SKY: Color = Color::rgb(0.1, 0.1, 0.1);

/// The fraction of its own light each loaded sky lands and reflects,
/// through [`SkyboxData::lit_by`]: the bright images fixed low, since an
/// image read too bright under the frame's own lights at its default
/// `1.0`; the dim images fixed more, since the scene read too dark under
/// them at the bright images' value.
const CLEAR_SKY_LIGHT: f32 = 0.35;
const CLASSIC_SKY_LIGHT: f32 = 0.35;
const DAWN_SKY_LIGHT: f32 = 0.3;
const SINISTER_SKY_LIGHT: f32 = 0.6;
const LIGHT_BLUE_STARS_LIGHT: f32 = 0.8;
const BLUE_STARS_LIGHT: f32 = 0.8;

/// The shading pair's plain half: a sphere given the shared shading
/// material and no map.
#[derive(Catalog, Clone, Copy, PartialEq, Eq, Hash)]
struct ShadingPlain;

impl Mesh for ShadingPlain {
    fn build(&self, assets: &Assets) -> MeshData {
        sphere_with_material(assets, shading_material())
    }
}

/// The shading pair's mapped half: the same sphere and material, with its
/// shading map (occlusion, roughness and metallic) baked in.
#[derive(Catalog, Clone, Copy, PartialEq, Eq, Hash)]
struct ShadingMapped;

impl Mesh for ShadingMapped {
    fn build(&self, assets: &Assets) -> MeshData {
        sphere_with_material(assets, shading_material()).with_shading(shading_checker())
    }
}

/// The relief pair's plain half.
#[derive(Catalog, Clone, Copy, PartialEq, Eq, Hash)]
struct ReliefPlain;

impl Mesh for ReliefPlain {
    fn build(&self, assets: &Assets) -> MeshData {
        sphere_with_material(assets, relief_material())
    }
}

/// The relief pair's mapped half: the same sphere and material, with its
/// relief map baked in.
#[derive(Catalog, Clone, Copy, PartialEq, Eq, Hash)]
struct ReliefMapped;

impl Mesh for ReliefMapped {
    fn build(&self, assets: &Assets) -> MeshData {
        sphere_with_material(assets, relief_material()).with_relief(relief_bumps())
    }
}

/// The emissive pair's plain half.
#[derive(Catalog, Clone, Copy, PartialEq, Eq, Hash)]
struct EmissivePlain;

impl Mesh for EmissivePlain {
    fn build(&self, assets: &Assets) -> MeshData {
        cube_with_material(assets, emissive_material())
    }
}

/// The emissive pair's mapped half: the same cube and material, with its
/// emissive map baked in.
#[derive(Catalog, Clone, Copy, PartialEq, Eq, Hash)]
struct EmissiveMapped;

impl Mesh for EmissiveMapped {
    fn build(&self, assets: &Assets) -> MeshData {
        cube_with_material(assets, emissive_material()).with_emissive_map(emissive_checker())
    }
}

/// The front sphere: a draw overrides its material new every frame, in
/// place of a baked one.
#[derive(Catalog, Clone, Copy, PartialEq, Eq, Hash)]
struct Front;

impl Mesh for Front {
    fn build(&self, assets: &Assets) -> MeshData {
        Sphere {
            subdivisions: SPHERE_SUBDIVISIONS,
        }
        .build(assets)
    }
}

/// `BannerCloth`: a mesh split into columns along its span and placed at
/// its `x = 0` edge, so `Banner`'s wave curves it, not a single flat
/// quad. Its triangles are built twice: once as authored and once in the
/// other order, with the normal turned around, so the cloth draws from
/// both sides however its wave curves it.
#[derive(Catalog, Clone, Copy, PartialEq, Eq, Hash)]
struct BannerCloth;

impl Mesh for BannerCloth {
    fn build(&self, _: &Assets) -> MeshData {
        banner_mesh()
    }
}

// Everything this game draws: the ground plane, each map pair's plain and
// mapped half, the front sphere with its own live material, the built-in
// primitives the reflection row and the pillars beside it place per draw,
// and the displaced cloth.
meshes! {
    enum Shape {
        Plane,
        Sphere,
        Cube,
        ShadingPlain,
        ShadingMapped,
        ReliefPlain,
        ReliefMapped,
        EmissivePlain,
        EmissiveMapped,
        Front,
        BannerCloth,
    }
}

fn sphere_with_material(assets: &Assets, material: Material) -> MeshData {
    Sphere {
        subdivisions: SPHERE_SUBDIVISIONS,
    }
    .build(assets)
    .with_material(material)
}

fn cube_with_material(assets: &Assets, material: Material) -> MeshData {
    Cube.build(assets).with_material(material)
}

fn shading_material() -> Material {
    Material::lit(SHADING_TINT).roughness(0.5).metallic(0.5)
}

fn relief_material() -> Material {
    Material::lit(RELIEF_TINT).roughness(0.35)
}

fn emissive_material() -> Material {
    Material::color(EMISSIVE_BASE).emissive(EMISSIVE_GLOW)
}

/// A shading map whose checker goes between low occlusion, roughness and
/// metallic and full occlusion, roughness and metallic, so all three read
/// apart across [`ShadingMapped`].
fn shading_checker() -> ShadingData {
    ShadingData::rgba8(
        MAP_SIZE,
        checker_pixels(MAP_SIZE, SHADING_CELL, SHADING_LOW, SHADING_HIGH),
    )
}

/// An emissive map whose checker goes between full glow and none, so
/// [`EMISSIVE_GLOW`] shapes across [`EmissiveMapped`] instead of casting
/// whole.
fn emissive_checker() -> TextureData {
    TextureData::rgba8(
        MAP_SIZE,
        checker_pixels(MAP_SIZE, EMISSIVE_CELL, [0, 0, 0], [255, 255, 255]),
    )
}

fn checker_pixels(size: UVec2, cell: u32, low: [u8; 3], high: [u8; 3]) -> Vec<u8> {
    let mut pixels = Vec::with_capacity((size.x * size.y * 4) as usize);
    for y in 0..size.y {
        for x in 0..size.x {
            let on = ((x / cell) + (y / cell)).is_multiple_of(2);
            let [red, green, blue] = if on { high } else { low };
            pixels.extend_from_slice(&[red, green, blue, u8::MAX]);
        }
    }
    pixels
}

/// A relief whose normals turn across a wave that repeats over the map:
/// each texel's slope comes from the partial derivatives of a
/// `sin(u) * sin(v)` height field at `BUMP_SLOPE`'s peak, computed at that
/// texel and not sampled from any other.
fn relief_bumps() -> ReliefData {
    let size = MAP_SIZE;
    let turns = core::f32::consts::TAU * BUMP_WAVES;
    let mut pixels = Vec::with_capacity((size.x * size.y * 4) as usize);
    for y in 0..size.y {
        for x in 0..size.x {
            let u = (x as f32 + 0.5) / size.x as f32;
            let v = (y as f32 + 0.5) / size.y as f32;
            let slope_u = BUMP_SLOPE * (turns * u).cos() * (turns * v).sin();
            let slope_v = BUMP_SLOPE * (turns * u).sin() * (turns * v).cos();
            let normal = Vec3::new(-slope_u, -slope_v, 1.0).normalize();
            let encode = |signed: f32| ((signed * 0.5 + 0.5) * 255.0).round() as u8;
            pixels.extend_from_slice(&[encode(normal.x), encode(normal.y), encode(normal.z), 0]);
        }
    }
    ReliefData::normals(size, pixels)
}

/// `BannerCloth`'s vertices and indices, built twice over: the columns as
/// authored, facing `+Z`, and the same columns again facing `-Z`, their
/// triangles in the other order so both draw front side out.
fn banner_mesh() -> MeshData {
    let mut vertices = Vec::with_capacity(((BANNER_COLUMNS + 1) * 4) as usize);
    for normal in [Vec3::Z, Vec3::NEG_Z] {
        for column in 0..=BANNER_COLUMNS {
            let u = column as f32 / BANNER_COLUMNS as f32;
            let x = u * BANNER_WIDTH;
            for v in [0.0, 1.0] {
                vertices.push(Vertex::new(
                    Vec3::new(x, -v * BANNER_HEIGHT, 0.0),
                    normal,
                    Vec2::new(u, v),
                ));
            }
        }
    }

    let side = BANNER_COLUMNS + 1;
    let mut indices = Vec::with_capacity((BANNER_COLUMNS * 12) as usize);
    for column in 0..BANNER_COLUMNS {
        let top_left = column * 2;
        let bottom_left = top_left + 1;
        let top_right = top_left + 2;
        let bottom_right = top_left + 3;
        indices.extend([
            bottom_left,
            bottom_right,
            top_right,
            bottom_left,
            top_right,
            top_left,
        ]);

        let back = side * 2;
        indices.extend([
            back + top_right,
            back + bottom_right,
            back + bottom_left,
            back + top_left,
            back + top_right,
            back + bottom_left,
        ]);
    }

    MeshData::new(vertices, indices)
}

/// Displaced by a wave that grows away from its `x = 0` edge; casts the
/// shadow of where it was placed, unmoved by its own wave. Its one value
/// is the clock its wave slides on.
#[derive(Default, ShaderValues)]
struct Banner {
    time: f32,
}

impl SurfaceStyle for Banner {
    const PASS: DrawPass = DrawPass::Opaque;
    const DISPLACE: Option<&'static str> = Some(include_str!("material_playground_banner.wgsl"));
}

/// A surface that reads no light of the scene's own: it draws its own
/// pulsing tint, added over what is behind it, through the color it pulses
/// through and the clock the pulse is timed by.
#[derive(Default, ShaderValues)]
struct Field {
    tint: Color,
    time: f32,
}

impl SurfaceStyle for Field {
    const PASS: DrawPass = DrawPass::Additive;
    const SURFACE: Option<&'static str> = Some(include_str!("material_playground_field.wgsl"));
}

surface_styles! { enum Looks { Banner, Field } }

/// A whole scene lighting choice: it names a sky and, kept with it, the
/// sun that lights the scene, so a choice cannot leave the two apart.
/// `Dawn`, `Noon`, `Dusk` and `Night` each pair a gradient with a sun of
/// its own color and direction; `Clear`, `Classic`, `ImageDawn` and
/// `Sinister` each pair a loaded image with a sun that fits it, and
/// `LightBlueStars` and `BlueStars` pair a loaded space image with none;
/// `Default` is the engine's own grey sky and white sun.
///
/// [`Skyboxes`] proves every value at startup, so it must be [`Eq`] and
/// [`Hash`] over a fixed [`Skyboxes::catalog`] — a sky and sun a player
/// set to any color and direction live could never meet, since `f32` is
/// neither. This fixed, named set is the shape this file chose in its
/// place: the side area offers it as one row, and shows the chosen sky's
/// own light and its sun's own strength as text, read only, rather than
/// controls a game could not build from. See this example's report for
/// what that choice costs.
#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
enum Sky {
    Dawn,
    Noon,
    Dusk,
    Night,
    Clear,
    Classic,
    ImageDawn,
    Sinister,
    LightBlueStars,
    BlueStars,
    Default,
}

impl Sky {
    const ALL: [Sky; 11] = [
        Self::Dawn,
        Self::Noon,
        Self::Dusk,
        Self::Night,
        Self::Clear,
        Self::Classic,
        Self::ImageDawn,
        Self::Sinister,
        Self::LightBlueStars,
        Self::BlueStars,
        Self::Default,
    ];

    fn name(self) -> &'static str {
        match self {
            Self::Dawn => "dawn",
            Self::Noon => "noon",
            Self::Dusk => "dusk",
            Self::Night => "night",
            Self::Clear => "clear day",
            Self::Classic => "classic",
            Self::ImageDawn => "dawn image",
            Self::Sinister => "sinister night",
            Self::LightBlueStars => "light blue stars",
            Self::BlueStars => "blue stars",
            Self::Default => "default",
        }
    }

    /// The fraction of its own light this sky lands and reflects, through
    /// [`SkyboxData::lit_by`]: fixed per choice, so a bright one does not
    /// read too bright, and a dark one does not read too dark, under the
    /// frame's own lights.
    fn light(self) -> f32 {
        match self {
            Self::Dawn => 0.4,
            Self::Noon => 0.5,
            Self::Dusk => 0.35,
            Self::Night => 0.3,
            Self::Clear => CLEAR_SKY_LIGHT,
            Self::Classic => CLASSIC_SKY_LIGHT,
            Self::ImageDawn => DAWN_SKY_LIGHT,
            Self::Sinister => SINISTER_SKY_LIGHT,
            Self::LightBlueStars => LIGHT_BLUE_STARS_LIGHT,
            Self::BlueStars => BLUE_STARS_LIGHT,
            Self::Default => 1.0,
        }
    }

    /// The sun this choice pairs with its sky: direction, color and
    /// strength resolved together, so a choice cannot leave them apart.
    /// `None` for the two space images, which pair with no sun at all.
    fn sun(self) -> Option<(Vec3, Color, f32)> {
        match self {
            Self::Dawn => Some((
                Vec3::new(-1.0, -0.15, 0.05),
                Color::rgb(1.0, 0.7, 0.45),
                1.4,
            )),
            Self::Noon => Some((
                Vec3::new(-0.15, -1.0, -0.1),
                Color::rgb(1.0, 1.0, 0.98),
                1.6,
            )),
            Self::Dusk => Some((
                Vec3::new(1.0, -0.15, 0.05),
                Color::rgb(1.0, 0.55, 0.25),
                1.2,
            )),
            Self::Night => Some((
                Vec3::new(-0.3, -0.7, -0.6),
                Color::rgb(0.55, 0.65, 0.85),
                0.15,
            )),
            Self::Clear => Some((
                Vec3::new(-0.2, -1.0, -0.15),
                Color::rgb(1.0, 0.98, 0.9),
                1.5,
            )),
            Self::Classic => Some((
                Vec3::new(-0.4, -0.9, -0.2),
                Color::rgb(1.0, 0.95, 0.85),
                1.3,
            )),
            Self::ImageDawn => Some((Vec3::new(-1.0, -0.2, 0.1), Color::rgb(1.0, 0.75, 0.5), 1.1)),
            Self::Sinister => Some((Vec3::new(0.4, -0.5, -0.7), Color::rgb(0.4, 0.5, 0.75), 0.1)),
            Self::LightBlueStars | Self::BlueStars => None,
            Self::Default => Some((Vec3::new(-0.4, -1.0, -0.6), Color::WHITE, 1.0)),
        }
    }

    /// The color the sky reads under the horizon, through
    /// [`SkyboxData::with_ground`]: the floor as lit under this choice's own
    /// sun and [`Self::light`], so it moves with them, not only with the
    /// image. `None` for the gradient skies and `Default`, which need no
    /// ground, and for the two space images, which hold space below the
    /// horizon as well.
    fn ground(self) -> Option<Color> {
        match self {
            Self::Clear => Some(Color::rgb(0.501, 0.517, 0.449)),
            Self::Classic => Some(Color::rgb(0.420, 0.405, 0.379)),
            Self::ImageDawn => Some(Color::rgb(0.073, 0.053, 0.032)),
            Self::Sinister => Some(Color::rgb(0.012, 0.014, 0.020)),
            Self::Dawn
            | Self::Noon
            | Self::Dusk
            | Self::Night
            | Self::LightBlueStars
            | Self::BlueStars
            | Self::Default => None,
        }
    }
}

impl Catalog for Sky {
    fn catalog() -> Vec<Self> {
        Self::ALL.to_vec()
    }
}

impl Skyboxes for Sky {
    fn build(&self, assets: &Assets) -> SkyboxData {
        let sky = match self {
            Self::Dawn => SkyboxData::gradient(
                Color::rgb(0.55, 0.55, 0.75),
                Color::rgb(0.95, 0.6, 0.35),
                Color::rgb(0.12, 0.08, 0.06),
            ),
            Self::Noon => SkyboxData::gradient(
                Color::rgb(0.2, 0.45, 0.85),
                Color::rgb(0.75, 0.82, 0.9),
                Color::rgb(0.3, 0.3, 0.28),
            ),
            Self::Dusk => SkyboxData::gradient(
                Color::rgb(0.18, 0.1, 0.3),
                Color::rgb(0.85, 0.35, 0.2),
                Color::rgb(0.03, 0.02, 0.03),
            ),
            Self::Night => SkyboxData::gradient(
                Color::rgb(0.02, 0.02, 0.06),
                Color::rgb(0.05, 0.05, 0.1),
                Color::rgb(0.0, 0.0, 0.0),
            ),
            Self::Clear => assets.skybox("sky-clear"),
            Self::Classic => assets.skybox("sky-classic"),
            Self::ImageDawn => assets.skybox("sky-dawn"),
            Self::Sinister => assets.skybox("sky-sinister"),
            Self::LightBlueStars => assets.skybox("sky-stars-lightblue"),
            Self::BlueStars => assets.skybox("sky-stars-blue"),
            Self::Default => SkyboxData::gradient(DEFAULT_SKY, DEFAULT_SKY, DEFAULT_SKY),
        };
        let sky = match self.ground() {
            Some(ground) => sky.with_ground(ground),
            None => sky,
        };

        sky.lit_by(self.light())
    }
}

/// `color` scaled by `strength`, the value a [`Light`] reads.
fn scaled(color: Color, strength: f32) -> Color {
    Color::rgb(
        color.red * strength,
        color.green * strength,
        color.blue * strength,
    )
}

/// One light's color and strength, held apart from the position that
/// names it, plus whether it casts.
#[derive(Clone, Copy)]
struct Glow {
    color: Color,
    strength: f32,
    shadow: bool,
}

impl Glow {
    /// `color` scaled by `strength`, the value a [`Light`] reads.
    fn scaled(self) -> Color {
        scaled(self.color, self.strength)
    }
}

/// Every key and button this game reads apart from the UI: held, `Look`
/// turns the camera by the pointer's own motion, `Forward`/`Back`/
/// `Left`/`Right` move it along the view and to its side, and `Up`/
/// `Down` move it along the world's own up.
#[derive(InputButtonAction, Clone, Copy, PartialEq)]
enum Move {
    Forward,
    Back,
    Left,
    Right,
    Up,
    Down,
    Look,
}

impl InputButtonAction for Move {
    fn bindings(&self) -> Vec<ButtonBinding> {
        match self {
            Self::Forward => vec![Key::W.into()],
            Self::Back => vec![Key::S.into()],
            Self::Left => vec![Key::A.into()],
            Self::Right => vec![Key::D.into()],
            Self::Up => vec![Key::Space.into()],
            Self::Down => vec![Key::LeftShift.into()],
            Self::Look => vec![MouseButton::Right.into()],
        }
    }
}

/// The pointer's own motion, read only while [`Move::Look`] is held.
#[derive(InputAxis2Action, Clone, Copy, PartialEq)]
enum Turn {
    Look,
}

impl InputAxis2Action for Turn {
    fn bindings(&self) -> Vec<Axis2Binding> {
        match self {
            Self::Look => vec![Axis2Binding::pointer().scale(LOOK_SENSITIVITY)],
        }
    }
}

/// How far the wheel moved this frame, read to scale the move speed.
#[derive(InputAxisAction, Clone, Copy, PartialEq)]
enum Speed {
    Wheel,
}

impl InputAxisAction for Speed {
    fn bindings(&self) -> Vec<AxisBinding> {
        match self {
            Self::Wheel => vec![AxisBinding::from(WheelDelta::Up).scale(4.0)],
        }
    }
}

struct Controls;

impl InputActions for Controls {
    type Button = Move;
    type Axis = Speed;
    type Axis2 = Turn;
}

struct Playground {
    eye: Vec3,
    yaw: f32,
    pitch: f32,
    speed_scale: f32,

    sky: Sky,
    sun_shadow: bool,

    lamp: Glow,
    spotlight: Glow,

    front_tint: Color,
    front_roughness: f32,
    front_metallic: f32,
    shading_map_on: bool,
    relief_map_on: bool,
    emissive_map_on: bool,

    exposure: f32,
    bloom: f32,
}

impl Playground {
    fn init(ctx: &mut InitContext<'_, Self>) -> Result<Self, Error> {
        let _ = ctx;
        Ok(Self {
            eye: START_EYE,
            yaw: START_YAW,
            pitch: START_PITCH,
            speed_scale: 1.0,

            sky: Sky::Default,
            sun_shadow: true,

            lamp: Glow {
                color: Color::rgb(0.9, 0.55, 0.3),
                strength: 3.0,
                shadow: false,
            },
            spotlight: Glow {
                color: Color::rgb(0.4, 0.6, 1.0),
                strength: 6.0,
                shadow: true,
            },

            front_tint: Color::rgb(0.7, 0.25, 0.2),
            front_roughness: 0.4,
            front_metallic: 0.0,
            shading_map_on: true,
            relief_map_on: true,
            emissive_map_on: true,

            exposure: START_EXPOSURE,
            bloom: START_BLOOM,
        })
    }

    /// This frame's forward direction, from `yaw` (turning around the
    /// world's own up) and `pitch` (turning up or down).
    fn forward(&self) -> Vec3 {
        Vec3::new(
            -self.pitch.cos() * self.yaw.sin(),
            self.pitch.sin(),
            -self.pitch.cos() * self.yaw.cos(),
        )
    }

    /// The camera this frame draws from: `eye` looking along `forward`.
    fn camera(&self) -> Camera {
        Camera::new(
            View::look_at(self.eye, self.eye + self.forward()),
            Projection::perspective(CAMERA_FOV),
        )
    }

    /// A held `Move::Look` (the right mouse button) turns the camera by
    /// the pointer's own motion, the same way it moves: dragging right
    /// turns the view right and left turns it left, dragging down turns
    /// it to look further down at the scene, dragging up back toward the
    /// horizon. `W`/`A`/`S`/`D` move along the view and to its side,
    /// `Space`/`Left Shift` up and down, and the wheel scales how far
    /// each move goes. The `eye` is held above the ground plane wherever
    /// it moves.
    fn fly_camera(&mut self, ctx: &mut FrameContext<'_, Self>) {
        if !ctx.ui_wants_pointer() && ctx.down(Move::Look) {
            let look = ctx.axis2(Turn::Look);
            self.yaw -= look.x;
            self.pitch = (self.pitch + look.y).clamp(-PITCH_LIMIT, PITCH_LIMIT);
        }

        let wheel = ctx.axis(Speed::Wheel);
        if !ctx.ui_wants_pointer() && wheel != 0.0 {
            self.speed_scale =
                (self.speed_scale * SPEED_STEP.powf(wheel)).clamp(MIN_SPEED_SCALE, MAX_SPEED_SCALE);
        }

        let forward = self.forward();
        let right = Vec3::new(self.yaw.cos(), 0.0, -self.yaw.sin());
        let mut move_by = Vec3::ZERO;
        if ctx.down(Move::Forward) {
            move_by += forward;
        }
        if ctx.down(Move::Back) {
            move_by -= forward;
        }
        if ctx.down(Move::Right) {
            move_by += right;
        }
        if ctx.down(Move::Left) {
            move_by -= right;
        }
        if ctx.down(Move::Up) {
            move_by += Vec3::Y;
        }
        if ctx.down(Move::Down) {
            move_by -= Vec3::Y;
        }
        if move_by.length_squared() > 1.0 {
            move_by = move_by.normalize();
        }

        self.eye += move_by * MOVE_SPEED * self.speed_scale * ctx.dt().as_secs_f32();
        self.eye.y = self.eye.y.max(MIN_EYE_HEIGHT);
    }

    /// The material [`Front`] draws with, resolved new from its sliders
    /// every frame — the override [`Instance::material`] takes, in place
    /// of a baked one.
    fn front_material(&self) -> Material {
        Material::lit(self.front_tint)
            .roughness(self.front_roughness)
            .metallic(self.front_metallic)
    }

    /// Every draw this game makes: the ground, each map pair, the front
    /// sphere, the reflection row and the pillars beside it.
    fn draw_scene(&self, ctx: &mut FrameContext<'_, Self>) {
        ctx.draw(
            Plane
                .at(Transform::from_scale(Vec3::new(
                    GROUND_SIZE,
                    1.0,
                    GROUND_SIZE,
                )))
                .material(Material::lit(GROUND_COLOR).roughness(0.9)),
        );

        Self::draw_pair(
            ctx,
            SHADING_Z,
            SPHERE_RADIUS,
            ShadingPlain.at(Vec3::ZERO).into_set(),
            ShadingMapped.at(Vec3::ZERO).into_set(),
            self.shading_map_on,
        );
        Self::draw_pair(
            ctx,
            RELIEF_Z,
            SPHERE_RADIUS,
            ReliefPlain.at(Vec3::ZERO).into_set(),
            ReliefMapped.at(Vec3::ZERO).into_set(),
            self.relief_map_on,
        );
        Self::draw_pair(
            ctx,
            EMISSIVE_Z,
            CUBE_SIZE / 2.0,
            EmissivePlain.at(Vec3::ZERO).into_set(),
            EmissiveMapped.at(Vec3::ZERO).into_set(),
            self.emissive_map_on,
        );

        ctx.draw(
            Front
                .at(Transform::from_scale_rotation_translation(
                    Vec3::splat(FRONT_SCALE),
                    Quat::IDENTITY,
                    FRONT_POSITION,
                ))
                .material(self.front_material()),
        );

        self.draw_reflect_row(ctx);
        self.draw_outpost(ctx);
    }

    /// One pair at depth `z`, its centers `height` above the ground: `plain`
    /// on the left always, and on the right `mapped` where `mapped_on` is
    /// set, `plain` again where it is not — the same position drawing the
    /// same base material with and without the map.
    fn draw_pair(
        ctx: &mut FrameContext<'_, Self>,
        z: f32,
        height: f32,
        plain: Instance<Shape, Looks>,
        mapped: Instance<Shape, Looks>,
        mapped_on: bool,
    ) {
        ctx.draw(plain.clone().at(Vec3::new(-PAIR_HALF_SPACING, height, z)));
        let right = if mapped_on { mapped } else { plain };
        ctx.draw(right.at(Vec3::new(PAIR_HALF_SPACING, height, z)));
    }

    /// A row of built-in `Sphere` draws at rising roughness, each
    /// `metallic(1.0)` with its tint white, so what draws is the sky's own
    /// reflection alone.
    fn draw_reflect_row(&self, ctx: &mut FrameContext<'_, Self>) {
        let start = -REFLECT_ROW_SPACING * (REFLECT_ROW_COUNT as f32 - 1.0) / 2.0;
        for index in 0..REFLECT_ROW_COUNT {
            let x = start + index as f32 * REFLECT_ROW_SPACING;
            let roughness = index as f32 / (REFLECT_ROW_COUNT as f32 - 1.0);
            ctx.draw(
                Sphere {
                    subdivisions: SPHERE_SUBDIVISIONS,
                }
                .at(Transform::from_scale_rotation_translation(
                    Vec3::splat(REFLECT_ROW_RADIUS * 2.0),
                    Quat::IDENTITY,
                    Vec3::new(x, REFLECT_ROW_RADIUS, REFLECT_ROW_Z),
                ))
                .material(
                    Material::lit(Color::WHITE)
                        .roughness(roughness)
                        .metallic(1.0),
                ),
            );
        }
    }

    /// Three pillars and a pole a light can shadow, beside `Banner`'s
    /// displaced cloth and `Field`'s pulsing sphere — [`OUTPOST`] moves the
    /// whole group clear of the rest of the scene.
    fn draw_outpost(&self, ctx: &mut FrameContext<'_, Self>) {
        let clock = ctx.elapsed().as_secs_f32();

        for &(position, scale) in &PILLARS {
            ctx.draw(
                Cube.at(Transform::from_scale_rotation_translation(
                    scale,
                    Quat::IDENTITY,
                    OUTPOST + position,
                ))
                .material(Material::lit(Color::rgb(0.55, 0.5, 0.45))),
            );
        }

        ctx.draw(
            Cube.at(Transform::from_scale_rotation_translation(
                POLE_SCALE,
                Quat::IDENTITY,
                OUTPOST + POLE_POSITION,
            ))
            .material(Material::lit(Color::rgb(0.3, 0.24, 0.18))),
        );

        ctx.set_surface_style(Banner { time: clock });
        ctx.draw(
            BannerCloth
                .at(Transform::from_translation(OUTPOST + BANNER_MOUNT))
                .material(Material::lit(Color::rgb(0.75, 0.12, 0.12)))
                .surface_style::<Banner>(),
        );

        ctx.set_surface_style(Field {
            tint: Color::rgb(0.25, 0.75, 1.0),
            time: clock,
        });
        ctx.draw(
            Sphere { subdivisions: 2 }
                .at(Transform::from_scale_rotation_translation(
                    Vec3::splat(FIELD_ORB_SCALE),
                    Quat::IDENTITY,
                    OUTPOST + FIELD_ORB_POSITION,
                ))
                .material(Material::color(Color::BLACK))
                .surface_style::<Field>(),
        );
    }

    /// This frame's sun, lamp and spotlight, each `.shadow()` where its own
    /// flag is set. The sun's direction, color and strength come from the
    /// chosen [`Sky`], and is absent where the choice pairs with none; only
    /// its shadow flag is the player's own.
    fn lights(&self) -> Vec<Light> {
        let lamp = Light::point(LAMP_POSITION, self.lamp.scaled(), LAMP_RANGE);
        let spotlight = Light::spot(Spot {
            position: SPOT_POSITION,
            direction: SPOT_DIRECTION,
            color: self.spotlight.scaled(),
            range: SPOT_RANGE,
            angle: SPOT_ANGLE,
        });

        let mut lights = vec![
            if self.lamp.shadow {
                lamp.shadow()
            } else {
                lamp
            },
            if self.spotlight.shadow {
                spotlight.shadow()
            } else {
                spotlight
            },
        ];

        if let Some((direction, color, strength)) = self.sky.sun() {
            let sun = Light::directional(direction, scaled(color, strength));
            lights.push(if self.sun_shadow { sun.shadow() } else { sun });
        }

        lights
    }

    /// Every live knob, in a side area of fixed width so the scene stays
    /// visible beside it — the default sky reads as flat grey, so a
    /// control added straight to the bare UI layer would read as a slab
    /// across the window.
    fn controls(&mut self, ctx: &mut FrameContext<'_, Self>) {
        let tonemap = ctx.config().tonemap();
        let antialiasing = ctx.config().antialiasing();
        let shadow_resolution = ctx.config().shadow_resolution();

        ctx.ui(|ui| {
            egui::Panel::right("controls")
                .resizable(false)
                .default_size(300.0)
                .show(ui, |ui| {
                    egui::ScrollArea::vertical().show(ui, |ui| {
                        ui.label(
                            "right mouse button to look, W/A/S/D to move, \
                             space/shift up and down, wheel to scale speed",
                        );
                        ui.separator();
                        self.lighting_controls(ui);
                        ui.separator();
                        self.light_controls(ui);
                        ui.separator();
                        self.material_controls(ui);
                        ui.separator();
                        ui.label(format!(
                            "tone map {tonemap:?} \u{b7} antialiasing {antialiasing} \u{b7} \
                             shadow {shadow_resolution}px: set at startup, not live"
                        ));
                        ui.add(egui::Slider::new(&mut self.exposure, 0.1..=3.0).text("exposure"));
                        ui.add(egui::Slider::new(&mut self.bloom, 0.0..=1.0).text("bloom"));
                    });
                });
        });
    }

    fn lighting_controls(&mut self, ui: &mut egui::Ui) {
        ui.heading("lighting");
        for choice in Sky::ALL {
            ui.radio_value(&mut self.sky, choice, choice.name());
        }
        ui.label(format!("sky light {:.2}: set at startup", self.sky.light()));

        match self.sky.sun() {
            Some((_, color, strength)) => {
                color_swatch(ui, "sun", color);
                ui.label(format!("sun strength {strength:.2}: set by the choice"));
                ui.checkbox(&mut self.sun_shadow, "sun shadow");
            }
            None => {
                ui.label("no sun: set by the choice");
            }
        }
    }

    fn light_controls(&mut self, ui: &mut egui::Ui) {
        ui.heading("lights");
        glow_controls(ui, "lamp", &mut self.lamp);
        glow_controls(ui, "spotlight", &mut self.spotlight);
    }

    fn material_controls(&mut self, ui: &mut egui::Ui) {
        ui.heading("material");
        color_row(ui, "tint", &mut self.front_tint);
        ui.add(egui::Slider::new(&mut self.front_roughness, 0.0..=1.0).text("roughness"));
        ui.add(egui::Slider::new(&mut self.front_metallic, 0.0..=1.0).text("metallic"));
        ui.checkbox(
            &mut self.shading_map_on,
            "shading map: occlusion \u{b7} roughness \u{b7} metallic",
        );
        ui.checkbox(&mut self.relief_map_on, "relief map: bump normals");
        ui.checkbox(&mut self.emissive_map_on, "emissive map: per-texel glow");
    }
}

/// One light's own controls: a color, its strength and a shadow flag.
fn glow_controls(ui: &mut egui::Ui, label: &str, glow: &mut Glow) {
    ui.label(label);
    color_row(ui, "color", &mut glow.color);
    ui.add(egui::Slider::new(&mut glow.strength, 0.0..=8.0).text("strength"));
    ui.checkbox(&mut glow.shadow, "shadow");
}

/// One named control over `color`'s red, green and blue channels; alpha
/// stays `1.0`.
fn color_row(ui: &mut egui::Ui, label: &str, color: &mut Color) {
    let mut rgb = [color.red, color.green, color.blue];
    ui.horizontal(|ui| {
        ui.label(label);
        if ui.color_edit_button_rgb(&mut rgb).changed() {
            *color = Color::rgb(rgb[0], rgb[1], rgb[2]);
        }
    });
}

/// `color` shown, not changed: the sun's own color, resolved from the
/// chosen [`Sky`] and not a control the player sets on its own.
fn color_swatch(ui: &mut egui::Ui, label: &str, color: Color) {
    let mut rgb = [color.red, color.green, color.blue];
    ui.horizontal(|ui| {
        ui.label(label);
        ui.add_enabled_ui(false, |ui| {
            ui.color_edit_button_rgb(&mut rgb);
        });
    });
}

impl Game for Playground {
    type Meshes = Shape;
    type Sounds = NoSounds;
    type InputActions = Controls;
    type Skyboxes = Sky;
    type SurfaceStyles = Looks;
    type PostEffects = ();

    fn tick(&mut self, _ctx: &mut TickContext<'_, Self>) {}

    fn frame(&mut self, ctx: &mut FrameContext<'_, Self>) {
        self.fly_camera(ctx);
        ctx.set_camera(self.camera());
        ctx.set_skybox(self.sky);
        for light in self.lights() {
            ctx.light(light);
        }
        ctx.set_exposure(self.exposure);
        ctx.set_bloom(self.bloom);

        self.draw_scene(ctx);
        self.controls(ctx);
    }
}

fn main() {
    let config = Config::new("Mirage: material playground")
        .with_size(1280, 720)
        .with_assets([
            "examples/assets/sky-clear.png",
            "examples/assets/sky-classic.png",
            "examples/assets/sky-dawn.png",
            "examples/assets/sky-sinister.png",
            "examples/assets/sky-stars-lightblue.png",
            "examples/assets/sky-stars-blue.png",
        ]);

    run(config, Playground::init);
}