docs: function SimpleLightmapFilter(lightmapTexture, ambientColor, resolution) {
      PIXI.Filter.call(this,
          // vertex shader
          // vertex shader
          glslify('./simpleLightmap.vert'),
          // fragment shader
          glslify('./simpleLightmap.frag')
      );
      this.uniforms.u_lightmap = lightmapTexture;
      this.uniforms.resolution = new Float32Array(resolution || [1.0, 1.0]);
      this.uniforms.ambientColor =  new Float32Array(ambientColor);
  }