precision mediump float;

attribute vec2 aTexCoord;

varying vec2 vTexCoord;

​

void main() {

  //vec4 positionVec4 = vec4(aPosition, 1.0);

  //positionVec4.xy = positionVec4.xy * 2.0 - 1.0;

  //gl_Position = positionVec4;

    vTexCoord = aTexCoord;

​

  vec4 positionVec4 = vec4(aPosition, 1.0);

  positionVec4.xy = positionVec4.xy * 2.0 - 1.0;

  gl_Position = positionVec4;

}

​