text: let shaderTemplate = {
      lowp: 'precision lowp float;\n'
      , mediump: 'precision mediump float; \n'
      , highp: 'precision highp float; \n'
      , a_normal: ''
      , u_viewMat: 'uniform Matrix4 u_viewMat4;\n'
      , u_modelMat: 'uniform Matrix4 u_modelMat4;\n'
      , mainStart: 'void main(){\n'
      , mainEnd:'}\n'
  }