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 +1,87 @@
+import { describe, expect, it } from 'vitest';
+import {
+  circleShape,
+  frameShape,
+  hexShape,
+  polygonShape,
+  rectShape,
+  roundedRectShape,
+  shapeFromThree,
+  signedArea,
+} from './shapes.js';
+
+describe('shape generators', () => {
+  it('rectShape is a CCW unit-ish rectangle', () => {
+    const s = rectShape(2, 4);
+    expect(s.outline).toEqual([
+      [-1, -2],
+      [1, -2],
+      [1, 2],
+      [-1, 2],
+    ]);
+    expect(signedArea(s.outline)).toBeGreaterThan(0);
+  });
+
+  it('polygonShape produces a regular polygon with the right vertex count', () => {
+    const s = polygonShape(6, 2);
+    expect(s.outline).toHaveLength(6);
+    // All vertices on the circle of radius 2.
+    for (const [x, y] of s.outline) {
+      expect(Math.hypot(x!, y!)).toBeCloseTo(2, 5);
+    }
+    expect(signedArea(s.outline)).toBeGreaterThan(0);
+  });
+
+  it('hexShape is a pointy-top hexagon', () => {
+    const s = hexShape(1);
+    expect(s.outline).toHaveLength(6);
+    // Pointy-top: a vertex sits at the top (angle 90deg, max y).
+    const top = s.outline.reduce((a, b) => (b[1]! > a[1]! ? b : a));
+    expect(top[0]).toBeCloseTo(0, 5);
+    expect(top[1]).toBeCloseTo(1, 5);
+  });
+
+  it('circleShape approximates a circle', () => {
+    const s = circleShape(3, 64);
+    expect(s.outline).toHaveLength(64);
+    for (const [x, y] of s.outline) {
+      expect(Math.hypot(x!, y!)).toBeCloseTo(3, 5);
+    }
+  });
+
+  it('roundedRectShape clamps the corner radius', () => {
+    const s = roundedRectShape(2, 2, 5);
+    // Radius clamped to half the smaller dimension (1).
+    const minX = Math.min(...s.outline.map((p) => p[0]!));
+    const maxX = Math.max(...s.outline.map((p) => p[0]!));
+    expect(minX).toBeCloseTo(-1, 5);
+    expect(maxX).toBeCloseTo(1, 5);
+    expect(s.outline.length).toBe(4 * 4); // 4 corners * 4 segments
+  });
+
+  it('frameShape has a hole wound CW', () => {
+    const s = frameShape(4, 4, 2);
+    expect(s.outline).toHaveLength(4);
+    expect(s.holes).toHaveLength(1);
+    expect(signedArea(s.outline)).toBeGreaterThan(0);
+    expect(signedArea(s.holes![0]!)).toBeLessThan(0);
+  });
+
+  it('shapeFromThree converts three.js vectors', () => {
+    const fake = {
+      getPoints: () => [
+        { x: 0, y: 0 },
+        { x: 1, y: 0 },
+        { x: 1, y: 1 },
+      ],
+      getPointsHoles: () => [],
+    };
+    const s = shapeFromThree(fake);
+    expect(s.outline).toEqual([
+      [0, 0],
+      [1, 0],
+      [1, 1],
+    ]);
+    expect(s.holes).toBeUndefined();
+  });
+});