feat: Add Plane geometry creator.

src/lib/geometry/primitives/Box.ts

@@ -120,7 +120,6 @@ export function box(
   // build geometry
 
   const geometry = new Geometry();
-
   geometry.setIndices(new Int32AttributeAccessor(new Int32Array(indices), 1));
   geometry.attributeAccessors.set("position", new Float32AttributeAccessor(new Float32Array(vertices), 3));
   geometry.attributeAccessors.set("normal", new Float32AttributeAccessor(new Float32Array(normals), 3));

src/lib/geometry/primitives/Plane.ts

@@ -0,0 +1,73 @@
+//
+// based on PlaneGeometry from Three.js
+//
+// Authors:
+// * @bhouston
+//
+
+import { Float32AttributeAccessor, Int32AttributeAccessor } from "../AttributeAccessor";
+import { Geometry } from "../Geometry";
+
+export function plane(width = 1, height = 1, widthSegments = 1, heightSegments = 1): Geometry {
+  const widthHalf = width / 2;
+  const heightHalf = height / 2;
+
+  const gridX = Math.floor(widthSegments);
+  const gridY = Math.floor(heightSegments);
+
+  const gridX1 = gridX + 1;
+  const gridY1 = gridY + 1;
+
+  const segmentWidth = width / gridX;
+  const segmentHeight = height / gridY;
+
+  // buffers
+
+  const indices: number[] = [];
+  const vertices: number[] = [];
+  const normals: number[] = [];
+  const uvs: number[] = [];
+
+  // generate vertices, normals and uvs
+
+  for (let iy = 0; iy < gridY1; iy++) {
+    const y = iy * segmentHeight - heightHalf;
+
+    for (let ix = 0; ix < gridX1; ix++) {
+      const x = ix * segmentWidth - widthHalf;
+
+      vertices.push(x, -y, 0);
+
+      normals.push(0, 0, 1);
+
+      uvs.push(ix / gridX);
+      uvs.push(1 - iy / gridY);
+    }
+  }
+
+  // indices
+
+  for (let iy = 0; iy < gridY; iy++) {
+    for (let ix = 0; ix < gridX; ix++) {
+      const a = ix + gridX1 * iy;
+      const b = ix + gridX1 * (iy + 1);
+      const c = ix + 1 + gridX1 * (iy + 1);
+      const d = ix + 1 + gridX1 * iy;
+
+      // faces
+
+      indices.push(a, b, d);
+      indices.push(b, c, d);
+    }
+  }
+
+  // build geometry
+
+  const geometry = new Geometry();
+  geometry.setIndices(new Int32AttributeAccessor(new Int32Array(indices), 1));
+  geometry.attributeAccessors.set("position", new Float32AttributeAccessor(new Float32Array(vertices), 3));
+  geometry.attributeAccessors.set("normal", new Float32AttributeAccessor(new Float32Array(normals), 3));
+  geometry.attributeAccessors.set("uv", new Float32AttributeAccessor(new Float32Array(uvs), 2));
+
+  return geometry;
+}