uniform sampler2D sceneTex; // 0
float vx_offset = 0.5;
float rt_w = 500.0;
float rt_h = 500.0;
float pixel_w = 15.0;
float pixel_h = 10.0;

void main()
{
    vec2 uv = gl_TexCoord[ 0 ].xy;

    vec3 tc = vec3( 1.0, 0.0, 0.0 );
    if( uv.x < ( vx_offset - 0.005 ) )
    {
        float dx = pixel_w * ( 1. / rt_w );
        float dy = pixel_h * ( 1. / rt_h );
        vec2 coord = vec2( dx * floor( uv.x/dx ), dy * floor( uv.y / dy ));
        tc = texture2D( sceneTex, coord ).rgb;
    }
    else if( uv.x >= ( vx_offset + 0.005 ) )
    {
        tc = texture2D( sceneTex, uv ).rgb;
    }
    gl_FragColor = vec4( tc, 1.0 );
}