feat(mesh): add tile mesh generation package

Add @tts/mesh, a package for generating extruded tile meshes from 2D shapes. It provides shape generators (rect, hex, circle, rounded rect, frame), earcut-based tessellation of top/bottom faces with UVs, and outward-normal wall generation, combined into raw BufferGeometry-ready typed arrays.
2026-08-08 13:42:32 +08:00
parent 3b86a641aa
commit 14f83f476c
13 changed files with 782 additions and 0 deletions
@@ -0,0 +1,95 @@
+import { describe, expect, it } from 'vitest';
+import { extrudeShape, mergeFaces } from './extrude.js';
+import { rectShape, hexShape, circleShape, roundedRectShape } from './shapes.js';
+import { capFaces } from './tessellate.js';
+import { wallFaces } from './walls.js';
+import type { FaceGeometry } from './types.js';
+
+describe('extrudeShape', () => {
+  it('produces a closed, watertight box for a rectangle', () => {
+    const geo = extrudeShape(rectShape(2, 2), { height: 1 });
+    // 4 outline points: 2 caps * 4 + 4 walls * 2 = 16 vertices.
+    expect(geo.positions.length / 3).toBe(16);
+    expect(geo.normals.length / 3).toBe(16);
+    expect(geo.uvs.length / 2).toBe(16);
+    // 2 cap triangles * 2 + 4 wall quads * 2 = 12 triangles.
+    expect(geo.indices.length).toBe(12 * 3);
+  });
+
+  it('every triangle is non-degenerate (positive area in 3D)', () => {
+    const geo = extrudeShape(hexShape(1), { height: 0.5 });
+    for (let i = 0; i < geo.indices.length; i += 3) {
+      const a = geo.indices[i]! * 3;
+      const b = geo.indices[i + 1]! * 3;
+      const c = geo.indices[i + 2]! * 3;
+      const area = triangleArea(geo.positions, a, b, c);
+      expect(area).toBeGreaterThan(0);
+    }
+  });
+
+  it('extrudes circles and rounded rects', () => {
+    const circle = extrudeShape(circleShape(1, 32), { height: 0.2 });
+    expect(circle.positions.length / 3).toBe(32 * 2 + 32 * 2);
+    expect(circle.indices.length).toBeGreaterThan(0);
+
+    const rounded = extrudeShape(roundedRectShape(2, 2, 0.3, 4), { height: 0.2 });
+    expect(rounded.positions.length / 3).toBe(16 * 2 + 16 * 2);
+    expect(rounded.indices.length).toBeGreaterThan(0);
+  });
+
+  it('applies uv scales', () => {
+    const geo = extrudeShape(rectShape(2, 2), { height: 1, capUvScale: 2 });
+    // Top face bottom-left UV should be scaled by 2.
+    expect(geo.uvs[0]).toBeCloseTo(0, 5);
+    expect(geo.uvs[1]).toBeCloseTo(0, 5);
+    expect(geo.uvs[4]).toBeCloseTo(2, 5);
+  });
+});
+
+describe('mergeFaces', () => {
+  it('concatenates faces and rebases indices', () => {
+    const a: FaceGeometry = {
+      positions: [0, 0, 0, 1, 0, 0],
+      uvs: [0, 0, 1, 0],
+      normals: [0, 0, 1, 0, 0, 1],
+      indices: [0, 1, 0],
+    };
+    const b: FaceGeometry = {
+      positions: [2, 0, 0, 3, 0, 0],
+      uvs: [0, 0, 1, 0],
+      normals: [0, 0, 1, 0, 0, 1],
+      indices: [0, 1, 0],
+    };
+    const merged = mergeFaces([a, b]);
+    expect(merged.positions.length / 3).toBe(4);
+    // Second face's indices rebased by 2.
+    expect(merged.indices).toEqual(new Uint32Array([0, 1, 0, 2, 3, 2]));
+  });
+});
+
+function triangleArea(
+  positions: Float32Array,
+  a: number,
+  b: number,
+  c: number,
+): number {
+  const ax = positions[a]!;
+  const ay = positions[a + 1]!;
+  const az = positions[a + 2]!;
+  const bx = positions[b]!;
+  const by = positions[b + 1]!;
+  const bz = positions[b + 2]!;
+  const cx = positions[c]!;
+  const cy = positions[c + 1]!;
+  const cz = positions[c + 2]!;
+  const abx = bx - ax;
+  const aby = by - ay;
+  const abz = bz - az;
+  const acx = cx - ax;
+  const acy = cy - ay;
+  const acz = cz - az;
+  const crossX = aby * acz - abz * acy;
+  const crossY = abz * acx - abx * acz;
+  const crossZ = abx * acy - aby * acx;
+  return Math.hypot(crossX, crossY, crossZ) / 2;
+}