 boxBuilder = new BoxBuilder();
          boxBuilder.pushCube([0, 0, 0], BOX_SIZE);
          let boxPrimitive = boxBuilder.finishPrimitive(renderer);
          let boxMaterial = new PbrMaterial();
          boxMaterial.baseColorFactor.value = [0.1, 0.1, 0.1, 1]; // grey
          this.renderPrimitive = renderer.createRenderPrimitive(boxPrimitive, boxMaterial);

          this.addRenderPrimitive(this.renderPrimitive);

          mat4.identity(this.matrix);
          mat4.translate(this.matrix, this.matrix, 