uniform sampler2D texUnit;
uniform vec2 noiseTextureSize;
uniform vec2 texStartPos;

varying vec2 uv;

void main(void)
{
    vec2 uvNoise = vec2((texStartPos.xy + gl_FragCoord.xy) / noiseTextureSize);

    gl_FragColor = vec4(texture2D(texUnit, uvNoise).rrr, 0);
}