text: class App {
    constructor() {
      this.canvas = document.getElementsByTagName('canvas')[0];
      const engine = this.engine = Filament.Engine.create(this.canvas);
      this.scene = engine.createScene();
      this.triangle = Filament.EntityManager.get()
        .create();
      this.scene.addEntity(this.triangle);
      const TRIANGLE_POSITIONS = new Float32Array([
        1, 0,
        Math.cos(Math.PI * 2 / 3), Math.sin(Math.PI * 2 / 3),
        Math.cos(Math.PI * 4 / 3), Math.sin(Math.PI * 4 / 3),
      ]);
      const TRIANGLE_COLORS = new Uint32Array([0xffff0000, 0xff00ff00, 0xff0000ff]);
      const VertexAttribute = Filament.VertexAttribute;
      const AttributeType = Filament.VertexBuffer$AttributeType;
      this.vb = Filament.VertexBuffer.Builder()
        .vertexCount(3)
        .bufferCount(2)
        .attribute(VertexAttribute.POSITION, 0, AttributeType.FLOAT2, 0, 8)
        .attribute(VertexAttribute.COLOR, 1, AttributeType.UBYTE4, 0, 4)
        .normalized(VertexAttribute.COLOR)
        .build(engine);
      this.vb.setBufferAt(engine, 0, TRIANGLE_POSITIONS);
      this.vb.setBufferAt(engine, 1, TRIANGLE_COLORS);
      this.ib = Filament.IndexBuffer.Builder()
        .indexCount(3)
        .bufferType(Filament.IndexBuffer$IndexType.USHORT)
        .build(engine);
      this.ib.setBuffer(engine, new Uint16Array([0, 1, 2]));
      const mat = engine.createMaterial('triangle.filamat');
      const matinst = mat.getDefaultInstance();
      Filament.RenderableManager.Builder(1)
        .boundingBox([
          [-1, -1, -1],
          [1, 1, 1]
        ])
        .material(0, matinst)
        .geometry(0, Filament.RenderableManager$PrimitiveType.TRIANGLES, this.vb, this.ib)
        .build(engine, this.triangle);
      this.swapChain = engine.createSwapChain();
      this.renderer = engine.createRenderer();
      this.camera = engine.createCamera();
      this.view = engine.createView();
      this.view.setCamera(this.camera);
      this.view.setScene(this.scene);
      this.view.setClearColor([0.1, 0.2, 0.3, 1.0]); // blue-green background
      this.resize(); // adjust the initial viewport
      this.render = this.render.bind(this);
      this.resize = this.resize.bind(this);
      window.addEventListener('resize', this.resize);
      window.requestAnimationFrame(this.render);
    }
    render() {
      // Rotate the triangle.
      const radians = Date.now() / 1000;
      const transform = mat4.fromRotation(mat4.create(), radians, [0, 0, 1]);
      const tcm = this.engine.getTransformManager();
      const inst = tcm.getInstance(this.triangle);
      tcm.setTransform(inst, transform);
      inst.delete();
      // Render the frame.
      this.renderer.render(this.swapChain, this.view);
      window.requestAnimationFrame(this.render);
    }
    resize() {
      const dpr = window.devicePixelRatio;
      const width = this.canvas.width = window.innerWidth * dpr;
      const height = this.canvas.height = window.innerHeight * dpr;
      this.view.setViewport([0, 0, width, height]);
      const aspect = width / height;
      const Projection = Filament.Camera$Projection;
      this.camera.setProjection(Projection.ORTHO, -aspect, aspect, -1, 1, 0, 1);
    }
  }
  Filament.init(['triangle.filamat'], () => {
    window.app = new App()
  });
  