Implement native SimpleRenderer reference pipeline (#76)

crates/libremetaverse-rendering-simple/src/generated.rs

@@ -6,11 +6,11 @@
 #![allow(non_snake_case)]
 
 /// C# type: `T:LibreMetaverse.Rendering.SimpleRenderer`.
-pub struct SimpleRenderer;
+pub use crate::simple_renderer::SimpleRenderer;
 impl SimpleRenderer {
     /// C# member: `M:LibreMetaverse.Rendering.SimpleRenderer.#ctor`.
     pub fn new() -> Result<Self, crate::Error> {
-        libremetaverse_types::not_implemented("M:LibreMetaverse.Rendering.SimpleRenderer.#ctor")
+        Self::native_new()
     }
     /// C# member: `M:LibreMetaverse.Rendering.SimpleRenderer.GenerateFacetedMesh(LibreMetaverse.Primitive,LibreMetaverse.Rendering.DetailLevel)`.
     pub fn generate_faceted_mesh(
@@ -18,9 +18,7 @@ impl SimpleRenderer {
         prim: libremetaverse::Primitive,
         lod: libremetaverse::rendering::DetailLevel,
     ) -> Result<libremetaverse::rendering::FacetedMesh, crate::Error> {
-        libremetaverse_types::not_implemented(
-            "M:LibreMetaverse.Rendering.SimpleRenderer.GenerateFacetedMesh(LibreMetaverse.Primitive,LibreMetaverse.Rendering.DetailLevel)",
-        )
+        self.native_generate_faceted_mesh(prim, lod)
     }
     /// C# member: `M:LibreMetaverse.Rendering.SimpleRenderer.GenerateFacetedSculptMesh(LibreMetaverse.Primitive,LibreMetaverse.Imaging.ManagedImage,LibreMetaverse.Rendering.DetailLevel)`.
     pub fn generate_faceted_sculpt_mesh(
@@ -29,9 +27,7 @@ impl SimpleRenderer {
         sculpt_texture: libremetaverse_imaging::ManagedImage,
         lod: libremetaverse::rendering::DetailLevel,
     ) -> Result<libremetaverse::rendering::FacetedMesh, crate::Error> {
-        libremetaverse_types::not_implemented(
-            "M:LibreMetaverse.Rendering.SimpleRenderer.GenerateFacetedSculptMesh(LibreMetaverse.Primitive,LibreMetaverse.Imaging.ManagedImage,LibreMetaverse.Rendering.DetailLevel)",
-        )
+        self.native_generate_faceted_sculpt_mesh(prim, sculpt_texture, lod)
     }
     /// C# member: `M:LibreMetaverse.Rendering.SimpleRenderer.GenerateSimpleMesh(LibreMetaverse.Primitive,LibreMetaverse.Rendering.DetailLevel)`.
     pub fn generate_simple_mesh(
@@ -39,9 +35,7 @@ impl SimpleRenderer {
         prim: libremetaverse::Primitive,
         lod: libremetaverse::rendering::DetailLevel,
     ) -> Result<libremetaverse::rendering::SimpleMesh, crate::Error> {
-        libremetaverse_types::not_implemented(
-            "M:LibreMetaverse.Rendering.SimpleRenderer.GenerateSimpleMesh(LibreMetaverse.Primitive,LibreMetaverse.Rendering.DetailLevel)",
-        )
+        self.native_generate_simple_mesh(prim, lod)
     }
     /// C# member: `M:LibreMetaverse.Rendering.SimpleRenderer.GenerateSimpleSculptMesh(LibreMetaverse.Primitive,LibreMetaverse.Imaging.ManagedImage,LibreMetaverse.Rendering.DetailLevel)`.
     pub fn generate_simple_sculpt_mesh(
@@ -50,9 +44,7 @@ impl SimpleRenderer {
         sculpt_texture: libremetaverse_imaging::ManagedImage,
         lod: libremetaverse::rendering::DetailLevel,
     ) -> Result<libremetaverse::rendering::SimpleMesh, crate::Error> {
-        libremetaverse_types::not_implemented(
-            "M:LibreMetaverse.Rendering.SimpleRenderer.GenerateSimpleSculptMesh(LibreMetaverse.Primitive,LibreMetaverse.Imaging.ManagedImage,LibreMetaverse.Rendering.DetailLevel)",
-        )
+        self.native_generate_simple_sculpt_mesh(prim, sculpt_texture, lod)
     }
     /// C# member: `M:LibreMetaverse.Rendering.SimpleRenderer.TransformTexCoords(System.Collections.Generic.List{LibreMetaverse.Rendering.Vertex},LibreMetaverse.Vector3,LibreMetaverse.Primitive.TextureEntryFace,LibreMetaverse.Vector3)`.
     pub fn transform_tex_coords(
@@ -62,9 +54,6 @@ impl SimpleRenderer {
         te_face: libremetaverse::PrimitiveTextureEntryFace,
         prim_scale: libremetaverse_types::Vector3,
     ) -> Result<(), crate::Error> {
-        libremetaverse_types::not_implemented(
-            "M:LibreMetaverse.Rendering.SimpleRenderer.TransformTexCoords(System.Collections.Generic.List{LibreMetaverse.Rendering.Vertex},LibreMetaverse.Vector3,LibreMetaverse.Primitive.TextureEntryFace,LibreMetaverse.Vector3)",
-        )
+        self.native_transform_tex_coords(vertices, center, te_face, prim_scale)
     }
 }
-impl libremetaverse::rendering::IRendering for SimpleRenderer {}

crates/libremetaverse-rendering-simple/src/lib.rs

@@ -1,8 +1,13 @@
-//! Simple renderer corresponding to `LibreMetaverse.Rendering.Simple`.
+//! Deterministic reference rendering for legacy prims and decoded sculpt maps.
+//!
+//! [`SimpleRenderer`] converts checked `PrimMesher` geometry into the shared
+//! rendering types without a graphics backend. See the crate README for the
+//! supported topology, resource bounds, and mesh-asset boundary.
 
 extern crate self as libremetaverse_rendering_simple;
 
 mod generated;
+mod simple_renderer;
 
 pub use generated::*;
 pub use libremetaverse as core;

crates/libremetaverse-rendering-simple/src/simple_renderer.rs

@@ -0,0 +1,665 @@
+//! Deterministic reference renderer built on the checked native prim mesher.
+
+#![allow(clippy::cast_possible_truncation)] // Checked C# float-to-int twist conversion.
+#![allow(clippy::missing_errors_doc)] // Public signatures are fixed by the API mapping.
+#![allow(clippy::must_use_candidate)] // Attributes are not part of the mapped surface.
+#![allow(clippy::needless_pass_by_value)] // Mapped value parameters are owned.
+#![allow(clippy::unnecessary_wraps)] // The mapped constructor is fallible in the C# API.
+#![allow(clippy::unused_self)] // IRendering exposes these operations as instance methods.
+
+use libremetaverse::rendering::{
+    DetailLevel, Face, FaceMask, FacetedMesh, IRendering, SimpleMesh, Vertex,
+};
+use libremetaverse::{MappingType, Primitive, PrimitiveTextureEntryFace};
+use libremetaverse_imaging::ManagedImage;
+use libremetaverse_prim_mesher::{
+    PathType, PrimMesh, SculptMesh, SculptMeshSculptType, VertexIndexer,
+};
+use libremetaverse_types::compat::Object;
+use libremetaverse_types::{
+    Error, HoleType, PathCurve, ProfileCurve, SculptType, Vector2, Vector3,
+};
+
+const MAX_FACE_VERTICES: usize = 65_536;
+const MAX_TOTAL_VERTICES: usize = MAX_FACE_VERTICES;
+const MAX_TOTAL_INDICES: usize = MAX_TOTAL_VERTICES * 6;
+
+/// Small, deterministic renderer for prim and sculpt geometry.
+pub struct SimpleRenderer;
+
+impl SimpleRenderer {
+    pub(crate) fn native_new() -> Result<Self, Error> {
+        Ok(Self)
+    }
+
+    pub(crate) fn native_generate_simple_mesh(
+        &self,
+        prim: Primitive,
+        lod: DetailLevel,
+    ) -> Result<SimpleMesh, Error> {
+        let source = prim.id;
+        let faceted = self.native_generate_faceted_mesh(prim, lod)?;
+        flatten_faces(faceted.faces, source)
+    }
+
+    pub(crate) fn native_generate_simple_sculpt_mesh(
+        &self,
+        prim: Primitive,
+        sculpt_texture: ManagedImage,
+        lod: DetailLevel,
+    ) -> Result<SimpleMesh, Error> {
+        let source = prim.id;
+        let faceted = self.native_generate_faceted_sculpt_mesh(prim, sculpt_texture, lod)?;
+        flatten_faces(faceted.faces, source)
+    }
+
+    pub(crate) fn native_generate_faceted_mesh(
+        &self,
+        prim: Primitive,
+        lod: DetailLevel,
+    ) -> Result<FacetedMesh, Error> {
+        let source = prim.id;
+        let mesh = generate_prim_mesh(&prim, lod, source)?;
+        let indexer = mesh
+            .get_vertex_indexer()
+            .map_err(|_| render_error(source, "index primitive viewer faces"))?
+            .ok_or_else(|| render_error(source, "primitive viewer faces are unavailable"))?;
+        let faces = indexed_faces(&prim, indexer, source)?;
+        Ok(FacetedMesh {
+            faces,
+            skin_data: None,
+        })
+    }
+
+    pub(crate) fn native_generate_faceted_sculpt_mesh(
+        &self,
+        prim: Primitive,
+        sculpt_texture: ManagedImage,
+        lod: DetailLevel,
+    ) -> Result<FacetedMesh, Error> {
+        let source = prim.id;
+        let sculpt = prim
+            .sculpt
+            .as_ref()
+            .ok_or_else(|| render_error(source, "primitive has no sculpt metadata"))?;
+        let sculpt_type = match sculpt.type_() {
+            SculptType::Cylinder => SculptMeshSculptType::Cylinder,
+            SculptType::Plane => SculptMeshSculptType::Plane,
+            SculptType::Sphere => SculptMeshSculptType::Sphere,
+            SculptType::Torus => SculptMeshSculptType::Torus,
+            SculptType::Mesh => {
+                return Err(render_error(
+                    source,
+                    "mesh sculpt requires a decoded mesh asset",
+                ));
+            }
+            SculptType::None | SculptType::Invert | SculptType::Mirror => {
+                return Err(render_error(source, "unsupported sculpt topology"));
+            }
+        };
+        let mesher_lod = match lod {
+            DetailLevel::Highest | DetailLevel::High => 32,
+            DetailLevel::Medium => 16,
+            DetailLevel::Low => 8,
+        };
+        let mesh = SculptMesh::new_with_managed_image_sculpt_type_int32_boolean_boolean_boolean(
+            sculpt_texture,
+            sculpt_type,
+            mesher_lod,
+            true,
+            sculpt.mirror(),
+            sculpt.invert(),
+        )
+        .map_err(|_| render_error(source, "generate bounded sculpt geometry"))?;
+        if mesh.coords.len() > MAX_FACE_VERTICES
+            || mesh.coords.len() != mesh.normals.len()
+            || mesh.coords.len() != mesh.uvs.len()
+        {
+            return Err(render_error(source, "invalid sculpt vertex domains"));
+        }
+        let vertices = mesh
+            .coords
+            .iter()
+            .zip(&mesh.normals)
+            .zip(&mesh.uvs)
+            .map(|((position, normal), uv)| {
+                checked_vertex(
+                    Vector3 {
+                        x: position.x,
+                        y: position.y,
+                        z: position.z,
+                    },
+                    Vector3 {
+                        x: normal.x,
+                        y: normal.y,
+                        z: normal.z,
+                    },
+                    Vector2 { x: uv.u, y: uv.v },
+                    source,
+                )
+            })
+            .collect::<Result<Vec<_>, _>>()?;
+        let mut indices = Vec::with_capacity(
+            mesh.faces
+                .len()
+                .checked_mul(3)
+                .ok_or_else(|| render_error(source, "sculpt index count overflow"))?,
+        );
+        for face in mesh.faces {
+            push_triangle(
+                &mut indices,
+                face.v1,
+                face.v2,
+                face.v3,
+                vertices.len(),
+                source,
+            )?;
+        }
+        let texture = texture_for_face(&prim, 0, source)?;
+        let face = make_face(0, vertices, indices, texture, source)?;
+        Ok(FacetedMesh {
+            faces: vec![face],
+            skin_data: None,
+        })
+    }
+
+    pub(crate) fn native_transform_tex_coords(
+        &self,
+        vertices: &mut Vec<Vertex>,
+        center: Vector3,
+        te_face: PrimitiveTextureEntryFace,
+        prim_scale: Vector3,
+    ) -> Result<(), Error> {
+        if !finite3(center)
+            || !finite3(prim_scale)
+            || ![
+                te_face.repeat_u(),
+                te_face.repeat_v(),
+                te_face.offset_u(),
+                te_face.offset_v(),
+                te_face.rotation(),
+            ]
+            .into_iter()
+            .all(f32::is_finite)
+        {
+            return Err(Error::Argument);
+        }
+        let cosine = te_face.rotation().cos();
+        let sine = te_face.rotation().sin();
+        for vertex in vertices {
+            if !finite3(vertex.position) || !finite3(vertex.normal) || !finite2(vertex.tex_coord) {
+                return Err(Error::Argument);
+            }
+            if te_face.tex_map_type() == MappingType::Planar {
+                let mut binormal;
+                let normal_x = vertex.normal.x;
+                if (-0.5..0.5).contains(&normal_x) {
+                    binormal = Vector3::unit_x();
+                    if vertex.normal.y > 0.0 {
+                        binormal.x = -1.0;
+                    }
+                } else {
+                    binormal = Vector3::unit_y();
+                    if normal_x < 0.0 {
+                        binormal.y = -1.0;
+                    }
+                }
+                let tangent = cross(binormal, vertex.normal);
+                let scaled = Vector3 {
+                    x: vertex.position.x * prim_scale.x,
+                    y: vertex.position.y * prim_scale.y,
+                    z: vertex.position.z * prim_scale.z,
+                };
+                vertex.tex_coord.x = 0.5 + dot(binormal, scaled) * 2.0;
+                vertex.tex_coord.y = 0.5 - dot(tangent, scaled) * 2.0;
+            }
+            let x = vertex.tex_coord.x - 0.5;
+            let y = vertex.tex_coord.y - 0.5;
+            vertex.tex_coord.x =
+                (x * cosine + y * sine) * te_face.repeat_u() + te_face.offset_u() + 0.5;
+            vertex.tex_coord.y =
+                (-x * sine + y * cosine) * te_face.repeat_v() + te_face.offset_v() + 0.5;
+            if !finite2(vertex.tex_coord) {
+                return Err(Error::Argument);
+            }
+        }
+        Ok(())
+    }
+}
+
+impl IRendering for SimpleRenderer {
+    fn generate_faceted_mesh(
+        &self,
+        prim: Primitive,
+        lod: DetailLevel,
+    ) -> Result<Option<FacetedMesh>, Error> {
+        self.native_generate_faceted_mesh(prim, lod).map(Some)
+    }
+
+    fn generate_faceted_sculpt_mesh(
+        &self,
+        prim: Primitive,
+        sculpt_texture: ManagedImage,
+        lod: DetailLevel,
+    ) -> Result<Option<FacetedMesh>, Error> {
+        self.native_generate_faceted_sculpt_mesh(prim, sculpt_texture, lod)
+            .map(Some)
+    }
+
+    fn generate_simple_mesh(
+        &self,
+        prim: Primitive,
+        lod: DetailLevel,
+    ) -> Result<Option<SimpleMesh>, Error> {
+        self.native_generate_simple_mesh(prim, lod).map(Some)
+    }
+
+    fn generate_simple_sculpt_mesh(
+        &self,
+        prim: Primitive,
+        sculpt_texture: ManagedImage,
+        lod: DetailLevel,
+    ) -> Result<Option<SimpleMesh>, Error> {
+        self.native_generate_simple_sculpt_mesh(prim, sculpt_texture, lod)
+            .map(Some)
+    }
+
+    fn transform_tex_coords(
+        &self,
+        vertices: &mut Vec<Vertex>,
+        center: Vector3,
+        te_face: PrimitiveTextureEntryFace,
+        prim_scale: Vector3,
+    ) -> Result<(), Error> {
+        self.native_transform_tex_coords(vertices, center, te_face, prim_scale)
+    }
+}
+
+fn generate_prim_mesh(
+    prim: &Primitive,
+    lod: DetailLevel,
+    source: libremetaverse_types::UUID,
+) -> Result<PrimMesh, Error> {
+    let data = &prim.prim_data;
+    let parameters = [
+        data.profile_begin,
+        data.profile_end,
+        data.profile_hollow,
+        data.path_scale_x,
+        data.path_scale_y,
+        data.path_begin,
+        data.path_end,
+        data.path_shear_x,
+        data.path_shear_y,
+        data.path_radius_offset,
+        data.path_revolutions,
+        data.path_skew,
+        data.path_taper_x,
+        data.path_taper_y,
+        data.path_twist_begin,
+        data.path_twist,
+    ];
+    if !parameters.into_iter().all(f32::is_finite) {
+        return Err(render_error(
+            source,
+            "non-finite primitive construction data",
+        ));
+    }
+    let (mut sides, mut profile_begin, mut profile_end, sphere_mode) =
+        match data.profile_curve_with_property() {
+            ProfileCurve::Circle => (lod_sides(lod), data.profile_begin, data.profile_end, false),
+            ProfileCurve::EqualTriangle
+            | ProfileCurve::IsoTriangle
+            | ProfileCurve::RightTriangle => (3, data.profile_begin, data.profile_end, false),
+            ProfileCurve::HalfCircle => (
+                lod_sides(lod),
+                data.profile_begin.mul_add(0.5, 0.5),
+                data.profile_end.mul_add(0.5, 0.5),
+                true,
+            ),
+            ProfileCurve::Square => (4, data.profile_begin, data.profile_end, false),
+        };
+    if sides < 3 {
+        sides = 3;
+    }
+    profile_begin = profile_begin.clamp(0.0, 1.0);
+    profile_end = profile_end.clamp(0.0, 1.0);
+    let hollow_sides = if data.profile_hole() == HoleType::Circle {
+        lod_sides(lod)
+    } else if data.profile_hole() == HoleType::Triangle {
+        3
+    } else if data.profile_hole() == HoleType::Same {
+        sides
+    } else {
+        4
+    };
+    let mut mesh = PrimMesh::new(
+        sides,
+        profile_begin,
+        profile_end,
+        data.profile_hollow,
+        hollow_sides,
+    )
+    .map_err(|_| render_error(source, "initialize primitive profile"))?;
+    mesh.viewer_mode = true;
+    mesh.sphere_mode = sphere_mode;
+    mesh.hole_size_x = data.path_scale_x;
+    mesh.hole_size_y = data.path_scale_y;
+    mesh.path_cut_begin = data.path_begin;
+    mesh.path_cut_end = data.path_end;
+    mesh.top_shear_x = data.path_shear_x;
+    mesh.top_shear_y = data.path_shear_y;
+    mesh.radius = data.path_radius_offset;
+    mesh.revolutions = data.path_revolutions;
+    mesh.skew = data.path_skew;
+    mesh.steps_per_revolution = lod_sides(lod);
+    let path_type = if matches!(data.path_curve, PathCurve::Line | PathCurve::Flexible) {
+        mesh.taper_x = 1.0 - data.path_scale_x;
+        mesh.taper_y = 1.0 - data.path_scale_y;
+        mesh.twist_begin = checked_twist(data.path_twist_begin, 180.0, source)?;
+        mesh.twist_end = checked_twist(data.path_twist, 180.0, source)?;
+        PathType::Linear
+    } else {
+        mesh.taper_x = data.path_taper_x;
+        mesh.taper_y = data.path_taper_y;
+        mesh.twist_begin = checked_twist(data.path_twist_begin, 360.0, source)?;
+        mesh.twist_end = checked_twist(data.path_twist, 360.0, source)?;
+        PathType::Circular
+    };
+    mesh.extrude(path_type)
+        .map_err(|_| render_error(source, "extrude primitive geometry"))?;
+    if mesh.coords.len() > MAX_TOTAL_VERTICES || mesh.viewer_faces.len() > MAX_TOTAL_INDICES / 3 {
+        return Err(render_error(
+            source,
+            "primitive geometry exceeds renderer bounds",
+        ));
+    }
+    Ok(mesh)
+}
+
+fn indexed_faces(
+    prim: &Primitive,
+    indexer: VertexIndexer,
+    source: libremetaverse_types::UUID,
+) -> Result<Vec<Face>, Error> {
+    let count = usize::try_from(indexer.num_prim_faces)
+        .map_err(|_| render_error(source, "invalid primitive face count"))?;
+    if count != indexer.viewer_vertices.len() || count != indexer.viewer_polygons.len() {
+        return Err(render_error(source, "misaligned primitive face domains"));
+    }
+    let mut total_vertices = 0usize;
+    let mut total_indices = 0usize;
+    let mut faces = Vec::with_capacity(count);
+    for face_index in 0..count {
+        let source_vertices = &indexer.viewer_vertices[face_index];
+        let polygons = indexer.viewer_polygons[face_index]
+            .as_ref()
+            .ok_or_else(|| render_error(source, "primitive face has no polygon domain"))?;
+        if source_vertices.is_empty() {
+            if polygons.is_empty() {
+                continue;
+            }
+            return Err(render_error(
+                source,
+                "primitive face polygons have no vertex domain",
+            ));
+        }
+        if source_vertices.len() > MAX_FACE_VERTICES {
+            return Err(render_error(
+                source,
+                "primitive face exceeds 16-bit vertex range",
+            ));
+        }
+        total_vertices = total_vertices
+            .checked_add(source_vertices.len())
+            .ok_or_else(|| render_error(source, "primitive vertex count overflow"))?;
+        if total_vertices > MAX_TOTAL_VERTICES {
+            return Err(render_error(source, "primitive vertex budget exceeded"));
+        }
+        let vertices = source_vertices
+            .iter()
+            .map(|vertex| {
+                checked_vertex(
+                    Vector3 {
+                        x: vertex.v.x,
+                        y: vertex.v.y,
+                        z: vertex.v.z,
+                    },
+                    Vector3 {
+                        x: vertex.n.x,
+                        y: vertex.n.y,
+                        z: vertex.n.z,
+                    },
+                    Vector2 {
+                        x: vertex.uv.u,
+                        y: 1.0 - vertex.uv.v,
+                    },
+                    source,
+                )
+            })
+            .collect::<Result<Vec<_>, _>>()?;
+        let mut indices = Vec::with_capacity(
+            polygons
+                .len()
+                .checked_mul(3)
+                .ok_or_else(|| render_error(source, "primitive index count overflow"))?,
+        );
+        for polygon in polygons {
+            if polygon.v1 == polygon.v2 || polygon.v1 == polygon.v3 || polygon.v2 == polygon.v3 {
+                continue;
+            }
+            push_triangle(
+                &mut indices,
+                polygon.v1,
+                polygon.v2,
+                polygon.v3,
+                vertices.len(),
+                source,
+            )?;
+        }
+        total_indices = total_indices
+            .checked_add(indices.len())
+            .ok_or_else(|| render_error(source, "primitive index count overflow"))?;
+        if total_indices > MAX_TOTAL_INDICES {
+            return Err(render_error(source, "primitive index budget exceeded"));
+        }
+        let texture = texture_for_face(prim, face_index, source)?;
+        faces.push(make_face(
+            i32::try_from(face_index)
+                .map_err(|_| render_error(source, "primitive face id overflow"))?,
+            vertices,
+            indices,
+            texture,
+            source,
+        )?);
+    }
+    Ok(faces)
+}
+
+fn flatten_faces(
+    faces: Vec<Face>,
+    source: libremetaverse_types::UUID,
+) -> Result<SimpleMesh, Error> {
+    let mut vertices = Vec::new();
+    let mut indices = Vec::new();
+    for face in faces {
+        let base = vertices.len();
+        let combined = base
+            .checked_add(face.vertices.len())
+            .ok_or_else(|| render_error(source, "simple mesh vertex count overflow"))?;
+        if combined > MAX_TOTAL_VERTICES {
+            return Err(render_error(
+                source,
+                "simple mesh exceeds 16-bit vertex range",
+            ));
+        }
+        for index in face.indices {
+            let global = base
+                .checked_add(usize::from(index))
+                .ok_or_else(|| render_error(source, "simple mesh index overflow"))?;
+            if global >= combined {
+                return Err(render_error(source, "simple mesh index is out of range"));
+            }
+            indices.push(
+                u16::try_from(global)
+                    .map_err(|_| render_error(source, "simple mesh index exceeds 16 bits"))?,
+            );
+        }
+        vertices.extend(face.vertices);
+    }
+    if indices.len() > MAX_TOTAL_INDICES {
+        return Err(render_error(source, "simple mesh index budget exceeded"));
+    }
+    Ok(SimpleMesh { indices, vertices })
+}
+
+fn texture_for_face(
+    prim: &Primitive,
+    index: usize,
+    source: libremetaverse_types::UUID,
+) -> Result<PrimitiveTextureEntryFace, Error> {
+    let Some(textures) = prim.textures.as_ref() else {
+        return Ok(PrimitiveTextureEntryFace::default());
+    };
+    let index =
+        u32::try_from(index).map_err(|_| render_error(source, "texture face index overflow"))?;
+    textures
+        .get_face(index)
+        .map_err(|_| render_error(source, "texture face index is out of range"))
+        .map(|face| face.cloned().unwrap_or_default())
+}
+
+fn make_face(
+    id: i32,
+    vertices: Vec<Vertex>,
+    indices: Vec<u16>,
+    texture_face: PrimitiveTextureEntryFace,
+    source: libremetaverse_types::UUID,
+) -> Result<Face, Error> {
+    let first = vertices
+        .first()
+        .ok_or_else(|| render_error(source, "render face has no vertices"))?;
+    let mut min = first.position;
+    let mut max = first.position;
+    for vertex in &vertices[1..] {
+        min.x = min.x.min(vertex.position.x);
+        min.y = min.y.min(vertex.position.y);
+        min.z = min.z.min(vertex.position.z);
+        max.x = max.x.max(vertex.position.x);
+        max.y = max.y.max(vertex.position.y);
+        max.z = max.z.max(vertex.position.z);
+    }
+    let center = Vector3 {
+        x: (min.x + max.x) * 0.5,
+        y: (min.y + max.y) * 0.5,
+        z: (min.z + max.z) * 0.5,
+    };
+    Ok(Face {
+        begin_s: 0,
+        begin_t: 0,
+        center,
+        edge: Vec::new(),
+        id,
+        indices,
+        mask: FaceMask::SINGLE,
+        max_extent: max,
+        min_extent: min,
+        normalized_scale: Vector3 {
+            x: max.x - min.x,
+            y: max.y - min.y,
+            z: max.z - min.z,
+        },
+        num_s: 0,
+        num_t: 0,
+        tex_coords1: None,
+        texture_face,
+        user_data: Object::Undefined,
+        vertices,
+        weights: None,
+    })
+}
+
+fn checked_vertex(
+    position: Vector3,
+    normal: Vector3,
+    tex_coord: Vector2,
+    source: libremetaverse_types::UUID,
+) -> Result<Vertex, Error> {
+    if !finite3(position) || !finite3(normal) || !finite2(tex_coord) {
+        return Err(render_error(
+            source,
+            "renderer produced a non-finite vertex",
+        ));
+    }
+    Ok(Vertex {
+        position,
+        normal,
+        tex_coord,
+    })
+}
+
+fn push_triangle(
+    indices: &mut Vec<u16>,
+    v1: i32,
+    v2: i32,
+    v3: i32,
+    vertex_count: usize,
+    source: libremetaverse_types::UUID,
+) -> Result<(), Error> {
+    for index in [v1, v2, v3] {
+        let index =
+            usize::try_from(index).map_err(|_| render_error(source, "negative renderer index"))?;
+        if index >= vertex_count {
+            return Err(render_error(source, "renderer index is out of range"));
+        }
+        indices.push(
+            u16::try_from(index)
+                .map_err(|_| render_error(source, "renderer index exceeds 16 bits"))?,
+        );
+    }
+    Ok(())
+}
+
+fn checked_twist(
+    value: f32,
+    multiplier: f32,
+    source: libremetaverse_types::UUID,
+) -> Result<i32, Error> {
+    let degrees = value * multiplier;
+    if !degrees.is_finite() || degrees.abs() > 360_000.0 {
+        return Err(render_error(source, "primitive twist is out of range"));
+    }
+    Ok(degrees as i32)
+}
+
+const fn lod_sides(lod: DetailLevel) -> i32 {
+    match lod {
+        DetailLevel::Low => 6,
+        DetailLevel::Medium => 12,
+        DetailLevel::High | DetailLevel::Highest => 24,
+    }
+}
+
+const fn render_error(source: libremetaverse_types::UUID, context: &'static str) -> Error {
+    Error::Rendering { source, context }
+}
+
+const fn finite2(value: Vector2) -> bool {
+    value.x.is_finite() && value.y.is_finite()
+}
+
+const fn finite3(value: Vector3) -> bool {
+    value.x.is_finite() && value.y.is_finite() && value.z.is_finite()
+}
+
+const fn dot(left: Vector3, right: Vector3) -> f32 {
+    left.x * right.x + left.y * right.y + left.z * right.z
+}
+
+const fn cross(left: Vector3, right: Vector3) -> Vector3 {
+    Vector3 {
+        x: left.y * right.z - left.z * right.y,
+        y: left.z * right.x - left.x * right.z,
+        z: left.x * right.y - left.y * right.x,
+    }
+}