attribute vec3 aVertexPosition;
      attribute vec4 aVertexColor;
      attribute vec2 aTextureCoord;
      
      uniform mat4 uMVMatrix;
      uniform mat4 uPMatrix;
      
      varying highp vec4 vColor;
      varying vec2 vTextureCoord;
      
      void main(void) {
        gl_Position = uPMatrix * uMVMatrix * vec4(aVertexPosition, 1.0);
        vColor = aVertexColor;
        vTextureCoord = aTextureCoord;
      }