perf: faster still

engine/scene/Mesh.ts

@@ -1,11 +1,26 @@
-import type { Vec2 } from "../math/Vec2"
-import type { Vec3 } from "../math/Vec3"
+/** Floats per vertex in `Mesh.verts`: position x, y, z then texture u, v. */
+export const STRIDE = 5
 
-/** One mesh vertex: a world-space position and its texture coordinate. uv is in
- *  tile units, not 0..1, so values >1 repeat the texture (see Texture.sample). */
-export type Vertex = { pos: Vec3; uv: Vec2 }
+/**
+ * Indexed triangle mesh, stored flat for speed. `verts` is a packed run of
+ * `STRIDE` floats per vertex (x, y, z, u, v) instead of an array of nested
+ * `{pos, uv}` objects, so the transform loop reads contiguous numbers with no
+ * pointer chasing or per-vertex allocation. `indices` holds three vertex indices
+ * per triangle (an index `i` addresses `verts[i * STRIDE ..]`); sharing vertices
+ * keeps seams welded and shrinks the data. uv is in tile units, not 0..1, so
+ * values >1 repeat the texture (see Texture.sample). Build with `Mesh.push`.
+ */
+export type Mesh = { verts: number[]; indices: number[] }
 
-/** Indexed triangle mesh in world space. `indices` holds three entries per
- *  triangle, each indexing into `vertices`; sharing vertices between triangles
- *  keeps seams welded and shrinks the data. */
-export type Mesh = { vertices: Vertex[]; indices: number[] }
+export namespace Mesh {
+  export function create(): Mesh {
+    return { verts: [], indices: [] }
+  }
+
+  /** Append a vertex, returning its index (for wiring up `indices`). */
+  export function push(mesh: Mesh, x: number, y: number, z: number, u: number, v: number): number {
+    const index = mesh.verts.length / STRIDE
+    mesh.verts.push(x, y, z, u, v)
+    return index
+  }
+}