//This relies on many globals, scroll down to view what you need vec4 sobel2() { vec4 ld = centre - lef; vec4 rd = centre - rig; vec4 ud = centre - up; vec4 dd = centre - dow; vec4 total = clamp(ld + rd + ud + dd, 0.0, 1.0); total.w = 1.0; return total; } //This was adapted from a different shader language