scena 1.7.2

A Rust-native scene-graph renderer with typed scene state, glTF assets, and explicit prepare/render lifecycles.
Documentation
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use std::collections::BTreeMap;

use super::super::super::error_diagnostic;
use super::super::common::{
    authored_color, positive_f64, primitive_size2, primitive_size3, u32_at_least, vec3,
};
use crate::geometry::{GeometryDesc, GeometryTopology, GeometryVertex};
use crate::scene::recipe::{
    SceneRecipeColorV1, SceneRecipeDiagnosticV1, SceneRecipeGeometryV1, SceneRecipeMeshV1,
    SceneRecipePrimitiveV1,
};
use crate::{Color, Vec3};

const SUPPORTED_PRIMITIVE_KINDS: &str =
    "box, plane, sphere, cylinder, cone, disc, torus, wedge, line, polyline, arrow, grid, axes";

pub(super) fn authored_geometry(
    recipe: &SceneRecipeGeometryV1,
    colors: &BTreeMap<String, SceneRecipeColorV1>,
) -> Result<(String, GeometryDesc), Box<SceneRecipeDiagnosticV1>> {
    if let Some(mesh) = &recipe.mesh {
        return authored_mesh(mesh, colors).map(|geometry| ("mesh".to_owned(), geometry));
    }
    let Some(primitive) = &recipe.primitive else {
        return Err(Box::new(error_diagnostic(
            "$",
            "missing_geometry_source",
            "geometry must include primitive or mesh",
            "emit either primitive:{...} or mesh:{...}",
        )));
    };
    match primitive.kind.as_str() {
        "box" => {
            let [width, height, depth] = primitive_size3(primitive).ok_or_else(|| {
                Box::new(error_diagnostic(
                    "$",
                    "invalid_primitive",
                    "box primitive requires a finite positive size",
                    "emit primitive:{kind:\"box\",size:[width,height,depth]}",
                ))
            })?;
            let bevel = primitive_bevel(primitive, width.min(height).min(depth) * 0.5)?;
            let geometry = if bevel > 0.0 {
                GeometryDesc::box_xyz_with_bevel(
                    width as f32,
                    height as f32,
                    depth as f32,
                    bevel as f32,
                )
            } else {
                GeometryDesc::box_xyz(width as f32, height as f32, depth as f32)
            };
            Ok(("box".to_owned(), geometry))
        }
        "plane" => {
            let [width, depth] = primitive_size2(primitive).ok_or_else(|| {
                Box::new(error_diagnostic(
                    "$",
                    "invalid_primitive",
                    "plane primitive requires finite positive size",
                    "emit primitive:{kind:\"plane\",size:[width,depth]}",
                ))
            })?;
            Ok((
                "plane".to_owned(),
                GeometryDesc::plane(width as f32, depth as f32),
            ))
        }
        "sphere" => {
            let radius = positive_f64(primitive.radius).ok_or_else(|| {
                Box::new(error_diagnostic(
                    "$",
                    "invalid_primitive",
                    "sphere primitive requires a finite positive radius",
                    "emit primitive:{kind:\"sphere\",radius}",
                ))
            })?;
            Ok((
                "sphere".to_owned(),
                GeometryDesc::sphere(
                    radius as f32,
                    primitive.segments.unwrap_or(64),
                    primitive.rings.unwrap_or(48),
                ),
            ))
        }
        "cylinder" => {
            let radius = positive_f64(primitive.radius).ok_or_else(|| {
                Box::new(error_diagnostic(
                    "$",
                    "invalid_primitive",
                    "cylinder primitive requires a finite positive radius",
                    "emit primitive:{kind:\"cylinder\",radius,height}",
                ))
            })?;
            let height = positive_f64(primitive.height).ok_or_else(|| {
                Box::new(error_diagnostic(
                    "$",
                    "invalid_primitive",
                    "cylinder primitive requires a finite positive height",
                    "emit primitive:{kind:\"cylinder\",radius,height}",
                ))
            })?;
            let bevel = primitive_bevel(primitive, radius.min(height * 0.5))?;
            let segments = primitive.segments.unwrap_or(32);
            let geometry = if bevel > 0.0 {
                GeometryDesc::cylinder_with_bevel(
                    radius as f32,
                    height as f32,
                    segments,
                    bevel as f32,
                )
            } else {
                GeometryDesc::cylinder(radius as f32, height as f32, segments)
            };
            Ok(("cylinder".to_owned(), geometry))
        }
        "cone" => {
            let radius = positive_f64(primitive.radius).ok_or_else(|| {
                Box::new(error_diagnostic(
                    "$",
                    "invalid_primitive",
                    "cone primitive requires a finite positive radius",
                    "emit primitive:{kind:\"cone\",radius,height,segments?}",
                ))
            })?;
            let height = positive_f64(primitive.height).ok_or_else(|| {
                Box::new(error_diagnostic(
                    "$",
                    "invalid_primitive",
                    "cone primitive requires a finite positive height",
                    "emit primitive:{kind:\"cone\",radius,height,segments?}",
                ))
            })?;
            let segments = u32_at_least(primitive.segments, 32, 3).ok_or_else(|| {
                Box::new(error_diagnostic(
                    "$",
                    "invalid_primitive",
                    "cone primitive segments must be at least 3",
                    "emit segments:3 or larger",
                ))
            })?;
            Ok((
                "cone".to_owned(),
                GeometryDesc::cone(radius as f32, height as f32, segments),
            ))
        }
        "disc" => {
            let radius = positive_f64(primitive.radius).ok_or_else(|| {
                Box::new(error_diagnostic(
                    "$",
                    "invalid_primitive",
                    "disc primitive requires a finite positive radius",
                    "emit primitive:{kind:\"disc\",radius,segments?}",
                ))
            })?;
            let segments = u32_at_least(primitive.segments, 32, 3).ok_or_else(|| {
                Box::new(error_diagnostic(
                    "$",
                    "invalid_primitive",
                    "disc primitive segments must be at least 3",
                    "emit segments:3 or larger",
                ))
            })?;
            Ok((
                "disc".to_owned(),
                GeometryDesc::disc(radius as f32, segments),
            ))
        }
        "torus" => {
            let major_radius = positive_f64(primitive.major_radius).ok_or_else(|| {
                Box::new(error_diagnostic(
                    "$",
                    "invalid_primitive",
                    "torus primitive requires a finite positive major_radius",
                    "emit primitive:{kind:\"torus\",major_radius,minor_radius}",
                ))
            })?;
            let minor_radius = positive_f64(primitive.minor_radius).ok_or_else(|| {
                Box::new(error_diagnostic(
                    "$",
                    "invalid_primitive",
                    "torus primitive requires a finite positive minor_radius",
                    "emit primitive:{kind:\"torus\",major_radius,minor_radius}",
                ))
            })?;
            if minor_radius >= major_radius {
                return Err(Box::new(error_diagnostic(
                    "$",
                    "invalid_primitive",
                    "torus minor_radius must be smaller than major_radius",
                    "use a tube radius below the torus major radius",
                )));
            }
            let segments = u32_at_least(primitive.segments, 32, 3).ok_or_else(|| {
                Box::new(error_diagnostic(
                    "$",
                    "invalid_primitive",
                    "torus primitive segments must be at least 3",
                    "emit segments:3 or larger",
                ))
            })?;
            let rings = u32_at_least(primitive.rings, 12, 3).ok_or_else(|| {
                Box::new(error_diagnostic(
                    "$",
                    "invalid_primitive",
                    "torus primitive rings must be at least 3",
                    "emit rings:3 or larger",
                ))
            })?;
            Ok((
                "torus".to_owned(),
                GeometryDesc::torus(major_radius as f32, minor_radius as f32, segments, rings),
            ))
        }
        "wedge" => {
            let [width, height, depth] = primitive_size3(primitive).ok_or_else(|| {
                Box::new(error_diagnostic(
                    "$",
                    "invalid_primitive",
                    "wedge primitive requires a finite positive size",
                    "emit primitive:{kind:\"wedge\",size:[width,height,depth]}",
                ))
            })?;
            Ok((
                "wedge".to_owned(),
                GeometryDesc::wedge(width as f32, height as f32, depth as f32),
            ))
        }
        "line" => {
            let start = primitive.start.ok_or_else(|| {
                Box::new(error_diagnostic(
                    "$",
                    "invalid_primitive",
                    "line primitive requires start",
                    "emit start:[x,y,z]",
                ))
            })?;
            let end = primitive.end.ok_or_else(|| {
                Box::new(error_diagnostic(
                    "$",
                    "invalid_primitive",
                    "line primitive requires end",
                    "emit end:[x,y,z]",
                ))
            })?;
            Ok((
                "line".to_owned(),
                GeometryDesc::line(vec3(start), vec3(end)),
            ))
        }
        "polyline" => Ok((
            "polyline".to_owned(),
            GeometryDesc::polyline(
                &primitive
                    .points
                    .iter()
                    .copied()
                    .map(vec3)
                    .collect::<Vec<_>>(),
            ),
        )),
        "arrow" => {
            let start = primitive.start.ok_or_else(|| {
                Box::new(error_diagnostic(
                    "$",
                    "invalid_primitive",
                    "arrow primitive requires start",
                    "emit start:[x,y,z]",
                ))
            })?;
            let end = primitive.end.ok_or_else(|| {
                Box::new(error_diagnostic(
                    "$",
                    "invalid_primitive",
                    "arrow primitive requires end",
                    "emit end:[x,y,z]",
                ))
            })?;
            Ok((
                "arrow".to_owned(),
                GeometryDesc::arrow(vec3(start), vec3(end)),
            ))
        }
        "grid" => {
            let size = positive_f64(
                primitive
                    .size
                    .as_ref()
                    .and_then(|size| size.first().copied()),
            )
            .or_else(|| positive_f64(primitive.length))
            .ok_or_else(|| {
                Box::new(error_diagnostic(
                    "$",
                    "invalid_primitive",
                    "grid primitive requires a finite positive size",
                    "emit primitive:{kind:\"grid\",size:[size],divisions?}",
                ))
            })?;
            Ok((
                "grid".to_owned(),
                GeometryDesc::grid(size as f32, primitive.divisions.unwrap_or(10)),
            ))
        }
        "axes" => {
            let length = positive_f64(primitive.length).ok_or_else(|| {
                Box::new(error_diagnostic(
                    "$",
                    "invalid_primitive",
                    "axes primitive requires a finite positive length",
                    "emit primitive:{kind:\"axes\",length}",
                ))
            })?;
            Ok(("axes".to_owned(), GeometryDesc::axes(length as f32)))
        }
        kind => Err(Box::new(error_diagnostic(
            "$",
            "unsupported_feature",
            format!("primitive kind '{kind}' is not supported"),
            format!("use one of: {SUPPORTED_PRIMITIVE_KINDS}"),
        ))),
    }
}

fn primitive_bevel(
    primitive: &SceneRecipePrimitiveV1,
    max_exclusive: f64,
) -> Result<f64, Box<SceneRecipeDiagnosticV1>> {
    match (primitive.bevel, primitive.fillet) {
        (Some(_), Some(_)) => Err(Box::new(error_diagnostic(
            "$",
            "invalid_primitive",
            "primitive may specify bevel or fillet, not both",
            "remove one bevel alias",
        ))),
        (Some(value), None) | (None, Some(value)) => {
            if !value.is_finite() || value <= 0.0 {
                return Err(Box::new(error_diagnostic(
                    "$",
                    "invalid_primitive",
                    "primitive bevel must be a finite positive distance",
                    "use a small bevel in meters below half the smallest primitive dimension",
                )));
            }
            if value >= max_exclusive {
                return Err(Box::new(error_diagnostic(
                    "$",
                    "invalid_primitive",
                    "primitive bevel must be smaller than half the limiting dimension",
                    "reduce bevel or enlarge the primitive",
                )));
            }
            Ok(value)
        }
        (None, None) => Ok(0.0),
    }
}

fn authored_mesh(
    mesh: &SceneRecipeMeshV1,
    colors: &BTreeMap<String, SceneRecipeColorV1>,
) -> Result<GeometryDesc, Box<SceneRecipeDiagnosticV1>> {
    let topology = match mesh.topology.as_str() {
        "triangles" => GeometryTopology::Triangles,
        "lines" => GeometryTopology::Lines,
        _ => {
            return Err(Box::new(error_diagnostic(
                "$",
                "unsupported_feature",
                format!("mesh topology '{}' is not supported", mesh.topology),
                "use topology:\"triangles\" or topology:\"lines\"",
            )));
        }
    };
    let vertices = mesh
        .positions
        .iter()
        .enumerate()
        .map(|(index, position)| GeometryVertex {
            position: vec3(*position),
            normal: mesh
                .normals
                .get(index)
                .copied()
                .map(vec3)
                .unwrap_or(Vec3::new(0.0, 1.0, 0.0)),
        })
        .collect::<Vec<_>>();
    let colors = if mesh.colors.is_empty() {
        vec![Color::WHITE; vertices.len()]
    } else {
        mesh.colors
            .iter()
            .map(|color| authored_color(colors, color).map_err(|diagnostic| *diagnostic))
            .collect::<Result<Vec<_>, _>>()
            .map_err(Box::new)?
    };
    let uvs = if mesh.uvs.is_empty() {
        vec![[0.0, 0.0]; vertices.len()]
    } else {
        mesh.uvs
            .iter()
            .map(|uv| [uv[0] as f32, uv[1] as f32])
            .collect::<Vec<_>>()
    };
    GeometryDesc::try_new_with_vertex_colors_and_tex_coords(
        topology,
        vertices,
        mesh.indices.clone(),
        colors,
        uvs,
    )
    .map_err(|error| {
        Box::new(error_diagnostic(
            "$",
            "invalid_mesh",
            format!("custom mesh is invalid: {error:?}"),
            "fix positions, normals, colors, uvs, and indices",
        ))
    })
}