generate a faceted mesh

src/crown_gear.rs

@@ -4,7 +4,7 @@ use glam::{Mat3A, Vec3, vec3};
 
 use crate::{
 	profile::Profile,
-	render::mesh::{CpuMeshIndexed, Vertex},
+	render::mesh::{MeshIndexed, Vertex},
 };
 
 #[derive(Debug, Clone, Copy)]
@@ -20,17 +20,17 @@ pub struct CrownGearVisual {
 	pub base_thickness: f32,
 }
 
-pub fn make_mesh(
+pub fn make_mesh_smooth(
 	desc: &CrownGearDesc,
 	visual: &CrownGearVisual,
 	sides: usize,
 	color: Vec3,
-) -> CpuMeshIndexed {
+) -> MeshIndexed {
 	let teeth = 2.0 * desc.pitch_radius;
 	let inner_scale = visual.inner_radius / desc.pitch_radius;
 	let outer_scale = visual.outer_radius / desc.pitch_radius;
 
-	let mut mesh = CpuMeshIndexed::new();
+	let mut mesh = MeshIndexed::new();
 	mesh.vertices.reserve_exact(8 * sides);
 	mesh.faces.reserve_exact(8 * sides);
 	for k in 0..sides {
@@ -81,3 +81,43 @@ pub fn make_mesh(
 	}
 	mesh
 }
+
+pub fn make_mesh_simple(
+	desc: &CrownGearDesc,
+	visual: &CrownGearVisual,
+	sides: usize,
+) -> MeshIndexed<Vec3> {
+	let teeth = 2.0 * desc.pitch_radius;
+	let inner_scale = visual.inner_radius / desc.pitch_radius;
+	let outer_scale = visual.outer_radius / desc.pitch_radius;
+
+	let mut mesh = MeshIndexed::new();
+	mesh.vertices.reserve_exact(4 * sides);
+	mesh.faces.reserve_exact(8 * sides);
+	for k in 0..sides {
+		let t = k as f32 / sides as f32;
+		let rot = Mat3A::from_rotation_z(2.0 * PI * t);
+
+		let tooth = t * teeth;
+		let y = desc.profile.y_from_tooth(tooth);
+
+		let vertex = |x, z| rot * vec3(x, 0.0, z);
+		mesh.vertices.extend([
+			vertex(visual.inner_radius, -visual.base_thickness),
+			vertex(visual.outer_radius, -visual.base_thickness),
+			vertex(visual.outer_radius, outer_scale * y),
+			vertex(visual.inner_radius, inner_scale * y),
+		]);
+
+		let base1 = 4 * k;
+		let base2 = 4 * ((k + 1) % sides);
+		for j1 in 0..4 {
+			let j2 = (j1 + 1) % 4;
+			mesh.faces
+				.push([base1 + j1, base2 + j1, base1 + j2].map(|index| index.try_into().unwrap()));
+			mesh.faces
+				.push([base2 + j2, base1 + j2, base2 + j1].map(|index| index.try_into().unwrap()));
+		}
+	}
+	mesh
+}

src/lib.rs

@@ -80,7 +80,7 @@ impl Core {
 
 		let depth = Self::create_depth_buffer(&device, pixel_size);
 		let mesh_pipeline = render::mesh::Pipeline::new(&device);
-		let crown_gear_mesh = crown_gear::make_mesh(
+		let crown_gear_mesh = crown_gear::make_mesh_simple(
 			&crown_gear::CrownGearDesc {
 				profile: Default::default(),
 				pitch_radius: 24.0,
@@ -91,8 +91,10 @@ impl Core {
 				base_thickness: 2.0,
 			},
 			600,
-			vec3(0.5, 0.5, 0.5),
-		);
+		)
+		.to_mesh()
+		.to_standard_mesh(vec3(0.5, 0.5, 0.5))
+		.into_indexed();
 		let mesh_gray = render::mesh::GpuMeshIndexed::new(&device, &crown_gear_mesh);
 
 		Self::configure_surface(&surface, &device, pixel_size);

src/render/mesh.rs

@@ -4,6 +4,10 @@ use bytemuck::{Pod, Zeroable, bytes_of, cast_slice};
 use glam::{Mat4, Vec3};
 use wgpu::util::DeviceExt;
 
+pub use cpu::*;
+
+mod cpu;
+
 static SHADER: &str = include_str!("mesh.wgsl");
 
 #[derive(Debug, Clone, Copy, Zeroable, Pod)]
@@ -22,23 +26,6 @@ pub struct Params {
 	pub _zero: f32,
 }
 
-#[derive(Debug, Clone, Default)]
-pub struct CpuMesh {
-	pub faces: Vec<[Vertex; 3]>,
-}
-
-#[derive(Debug, Clone, Default)]
-pub struct CpuMeshIndexed {
-	pub vertices: Vec<Vertex>,
-	pub faces: Vec<[u16; 3]>,
-}
-
-impl CpuMeshIndexed {
-	pub fn new() -> Self {
-		Self::default()
-	}
-}
-
 pub struct GpuMesh {
 	vertices: wgpu::Buffer,
 	vertex_count: u32,

src/render/mesh/cpu.rs

@@ -0,0 +1,102 @@
+use glam::Vec3;
+
+use super::Vertex;
+
+#[derive(Debug, Clone)]
+pub struct Mesh<T: Copy = Vertex> {
+	pub faces: Vec<[T; 3]>,
+}
+
+#[derive(Debug, Clone)]
+pub struct MeshIndexed<T: Copy = Vertex> {
+	pub vertices: Vec<T>,
+	pub faces: Vec<[u16; 3]>,
+}
+
+pub type CpuMesh = Mesh<Vertex>;
+pub type CpuMeshIndexed = MeshIndexed<Vertex>;
+
+impl<T: Copy> Mesh<T> {
+	pub fn new() -> Self {
+		Self { faces: Vec::new() }
+	}
+
+	pub fn concat(meshes: impl IntoIterator<Item = Self>) -> Self {
+		Self {
+			faces: meshes
+				.into_iter()
+				.map(|mesh| mesh.faces)
+				.flatten()
+				.collect(),
+		}
+	}
+
+	pub fn into_indexed(self) -> MeshIndexed<T> {
+		if self.faces.len() >= (1 << 16) / 3 {
+			panic!("too many faces");
+		}
+		let n_faces = self.faces.len() as u16;
+		MeshIndexed {
+			vertices: self.faces.into_iter().flatten().collect(),
+			faces: (0..n_faces)
+				.map(|face| [3 * face, 3 * face + 1, 3 * face + 2])
+				.collect(),
+		}
+	}
+}
+
+impl Mesh<Vec3> {
+	pub fn to_standard_mesh(&self, color: Vec3) -> CpuMesh {
+		CpuMesh {
+			faces: self
+				.faces
+				.iter()
+				.map(|face| {
+					let [a, b, c] = face;
+					let normal = (b - a).cross(c - a).normalize();
+					face.map(|position| Vertex {
+						position,
+						color,
+						normal,
+					})
+				})
+				.collect(),
+		}
+	}
+}
+
+impl<T: Copy> MeshIndexed<T> {
+	pub fn new() -> Self {
+		Self {
+			vertices: Vec::new(),
+			faces: Vec::new(),
+		}
+	}
+
+	pub fn concat(meshes: impl IntoIterator<Item = Self>) -> Self {
+		let mut ret = Self::new();
+		for mesh in meshes {
+			let base = ret.vertices.len() as u16;
+			ret.vertices.extend(mesh.vertices);
+			if ret.vertices.len() > 1 << 16 {
+				panic!("too many vertices");
+			}
+			ret.faces.extend(
+				mesh.faces
+					.into_iter()
+					.map(|face| face.map(|index| base + index)),
+			);
+		}
+		ret
+	}
+
+	pub fn to_mesh(&self) -> Mesh<T> {
+		Mesh {
+			faces: self
+				.faces
+				.iter()
+				.map(|face| face.map(|index| self.vertices[index as usize]))
+				.collect(),
+		}
+	}
+}