anchor.diff:    html.CanvasElement canvas;
     gl.RenderingContext ctx;
     PerspectiveCamera camera;
  -  double fov;
  -  Matrix4 projectionMatrix;
     Pass pass;
     Color backgroundColor = new Color.fromHex(0x84A6EE);
     List<Light> lights = [];
  
positive.code:     this.canvas = canvas;
      ctx = canvas.getContext3d();
      camera = new PerspectiveCamera(canvas.width / canvas.height);
      //    camera.distance = 4.0;
      //    camera.center = new Vector3.zero();
      fov = 45.0;
      //    projectionMatrix = new Matrix4.perspective(fov, canvas.width / canvas.height, 1.0, 4096.0);
  
      ctx.clearColor(backgroundColor.red, backgroundColor.green, backgroundColor.blue, backgroundColor.alpha);
      ctx.clearDepth(1.0);
  
negative.code:     shader.uniform(ctx, Semantics.useTextures, false);
  
      if (node is Light) {
        //      _drawLight(node);
      } else if (node is Mesh) {
        _drawMesh(node);
      }
  