refactor: move world concepts into engine

engine/scene/MeshBuilder.ts

@@ -0,0 +1,80 @@
+import { STRIDE, type Mesh } from "./Mesh"
+
+type Corner = [number, number, number]
+
+export namespace MeshBuilder {
+  export function quad(
+    mesh: Mesh,
+    a: Corner,
+    b: Corner,
+    c: Corner,
+    d: Corner,
+    uScale: number,
+    vScale: number,
+  ): void {
+    const base = mesh.verts.length / STRIDE
+    mesh.verts.push(
+      a[0],
+      a[1],
+      a[2],
+      0,
+      0,
+      b[0],
+      b[1],
+      b[2],
+      uScale,
+      0,
+      c[0],
+      c[1],
+      c[2],
+      uScale,
+      vScale,
+      d[0],
+      d[1],
+      d[2],
+      0,
+      vScale,
+    )
+    mesh.indices.push(base, base + 1, base + 2, base, base + 2, base + 3)
+  }
+
+  export function slab(
+    mesh: Mesh,
+    x0: number,
+    x1: number,
+    z0: number,
+    z1: number,
+    y0: number,
+    y1: number,
+    tilesPerUnit: number,
+  ): void {
+    const dx = (x1 - x0) * tilesPerUnit
+    const dz = (z1 - z0) * tilesPerUnit
+    const dy = (y1 - y0) * tilesPerUnit
+    quad(mesh, [x0, y1, z0], [x1, y1, z0], [x1, y1, z1], [x0, y1, z1], dx, dz)
+    quad(mesh, [x0, y0, z0], [x1, y0, z0], [x1, y1, z0], [x0, y1, z0], dx, dy)
+    quad(mesh, [x1, y0, z1], [x0, y0, z1], [x0, y1, z1], [x1, y1, z1], dx, dy)
+    quad(mesh, [x0, y0, z1], [x0, y0, z0], [x0, y1, z0], [x0, y1, z1], dz, dy)
+    quad(mesh, [x1, y0, z0], [x1, y0, z1], [x1, y1, z1], [x1, y1, z0], dz, dy)
+  }
+
+  export function box(
+    mesh: Mesh,
+    centerX: number,
+    centerZ: number,
+    half: number,
+    base: number,
+    height: number,
+  ): void {
+    const x0 = centerX - half
+    const x1 = centerX + half
+    const z0 = centerZ - half
+    const z1 = centerZ + half
+    const y1 = base + height
+    quad(mesh, [x0, y1, z0], [x1, y1, z0], [x1, y1, z1], [x0, y1, z1], 1, 1)
+    quad(mesh, [x0, base, z0], [x1, base, z0], [x1, y1, z0], [x0, y1, z0], 1, 1)
+    quad(mesh, [x1, base, z1], [x0, base, z1], [x0, y1, z1], [x1, y1, z1], 1, 1)
+    quad(mesh, [x1, base, z0], [x1, base, z1], [x1, y1, z1], [x1, y1, z0], 1, 1)
+    quad(mesh, [x0, base, z1], [x0, base, z0], [x0, y1, z0], [x0, y1, z1], 1, 1)
+  }
+}