anchor.diff:  
       varying vec4 vPosition;
       varying vec3 vNormal;
  +    varying vec3 vVertexNormal;
  +    varying vec3 vVertexPosition;
       varying vec2 vTextureCoord;
     
       uniform mat4 uMVMatrix;
  
positive.code:     _gl.uniformMatrix4fv(_uPMatrix, false, _pMatrix.storage);
      _gl.uniformMatrix4fv(_uMVMatrix, false, _mvMatrix.storage);
  
      //Matrix3 normalMatrix = _mvMatrix.toInverseMat3();
      Matrix3 normalMatrix = _mvMatrix.getRotation();
      normalMatrix.transpose();
      _gl.uniformMatrix3fv(_uNMatrix, false, normalMatrix.storage);
    }
  
  
negative.code:   }
  
    void _initShaders() {
      // vertex shader
      String vsSource = """
      attribute vec3 aVertexPosition;
      attribute vec3 aVertexNormal;
  