first commit

data-pipeline/scripts/geometry.mjs

@@ -0,0 +1,130 @@
+// Minimal parametric mesh generators (box/sphere/cylinder), dependency-free.
+// Returns { positions: Float32Array, normals: Float32Array, indices: Uint32Array }.
+
+export function box(w, h, d) {
+  const x = w / 2, y = h / 2, z = d / 2;
+  const positions = [];
+  const normals = [];
+  const indices = [];
+
+  const faces = [
+    // [normal, 4 corners CCW]
+    [[0, 0, 1], [[-x, -y, z], [x, -y, z], [x, y, z], [-x, y, z]]],
+    [[0, 0, -1], [[x, -y, -z], [-x, -y, -z], [-x, y, -z], [x, y, -z]]],
+    [[0, 1, 0], [[-x, y, z], [x, y, z], [x, y, -z], [-x, y, -z]]],
+    [[0, -1, 0], [[-x, -y, -z], [x, -y, -z], [x, -y, z], [-x, -y, z]]],
+    [[1, 0, 0], [[x, -y, z], [x, -y, -z], [x, y, -z], [x, y, z]]],
+    [[-1, 0, 0], [[-x, -y, -z], [-x, -y, z], [-x, y, z], [-x, y, -z]]],
+  ];
+
+  for (const [n, corners] of faces) {
+    const base = positions.length / 3;
+    for (const c of corners) {
+      positions.push(...c);
+      normals.push(...n);
+    }
+    indices.push(base, base + 1, base + 2, base, base + 2, base + 3);
+  }
+
+  return {
+    positions: new Float32Array(positions),
+    normals: new Float32Array(normals),
+    indices: new Uint32Array(indices),
+  };
+}
+
+export function sphere(radius, widthSegments = 16, heightSegments = 12) {
+  const positions = [];
+  const normals = [];
+  const indices = [];
+
+  for (let y = 0; y <= heightSegments; y++) {
+    const v = y / heightSegments;
+    const theta = v * Math.PI;
+    for (let x = 0; x <= widthSegments; x++) {
+      const u = x / widthSegments;
+      const phi = u * Math.PI * 2;
+      const nx = -Math.cos(phi) * Math.sin(theta);
+      const ny = Math.cos(theta);
+      const nz = Math.sin(phi) * Math.sin(theta);
+      positions.push(radius * nx, radius * ny, radius * nz);
+      normals.push(nx, ny, nz);
+    }
+  }
+
+  const rowSize = widthSegments + 1;
+  for (let y = 0; y < heightSegments; y++) {
+    for (let x = 0; x < widthSegments; x++) {
+      const a = y * rowSize + x;
+      const b = a + rowSize;
+      indices.push(a, b, a + 1, b, b + 1, a + 1);
+    }
+  }
+
+  return {
+    positions: new Float32Array(positions),
+    normals: new Float32Array(normals),
+    indices: new Uint32Array(indices),
+  };
+}
+
+export function cylinder(radiusTop, radiusBottom, height, radialSegments = 12) {
+  const positions = [];
+  const normals = [];
+  const indices = [];
+  const halfH = height / 2;
+
+  // Side wall.
+  for (let y = 0; y <= 1; y++) {
+    const r = y === 0 ? radiusTop : radiusBottom;
+    const py = y === 0 ? halfH : -halfH;
+    for (let x = 0; x <= radialSegments; x++) {
+      const u = (x / radialSegments) * Math.PI * 2;
+      const nx = Math.sin(u);
+      const nz = Math.cos(u);
+      positions.push(r * nx, py, r * nz);
+      const slope = (radiusBottom - radiusTop) / height;
+      const len = Math.sqrt(1 + slope * slope);
+      normals.push(nx / len, -slope / len, nz / len);
+    }
+  }
+  const rowSize = radialSegments + 1;
+  for (let x = 0; x < radialSegments; x++) {
+    const a = x, b = a + rowSize;
+    indices.push(a, b, a + 1, b, b + 1, a + 1);
+  }
+
+  // Caps.
+  function cap(y, r, py, flip) {
+    const base = positions.length / 3;
+    const ny = flip ? 1 : -1;
+    positions.push(0, py, 0);
+    normals.push(0, ny, 0);
+    for (let x = 0; x <= radialSegments; x++) {
+      const u = (x / radialSegments) * Math.PI * 2;
+      positions.push(r * Math.sin(u), py, r * Math.cos(u));
+      normals.push(0, ny, 0);
+    }
+    for (let x = 0; x < radialSegments; x++) {
+      if (flip) indices.push(base, base + x + 2, base + x + 1);
+      else indices.push(base, base + x + 1, base + x + 2);
+    }
+  }
+  if (radiusTop > 0) cap(0, radiusTop, halfH, true);
+  if (radiusBottom > 0) cap(1, radiusBottom, -halfH, false);
+
+  return {
+    positions: new Float32Array(positions),
+    normals: new Float32Array(normals),
+    indices: new Uint32Array(indices),
+  };
+}
+
+export function buildGeometry(shape) {
+  switch (shape.type) {
+    case "box": return box(shape.w, shape.h, shape.d);
+    case "sphere": return sphere(shape.r);
+    case "cylinder": return cylinder(shape.rt, shape.rb, shape.h);
+    default: throw new Error(`Unknown shape type: ${shape.type}`);
+  }
+}