uniform half4 testInputs; // equals (-1.25, 0, 0.75, 2.25) uniform half4 colorGreen, colorRed; half4 main(float2 coords) { half4 expected = half4(0); // derivative of a constant is zero return (dFdx(testInputs.x) == expected.x && dFdx(testInputs.xy) == expected.xy && dFdx(testInputs.xyz) == expected.xyz && dFdx(testInputs.xyzw) == expected.xyzw && sign(dFdy(coords.xx)) == half2(0, 0) && sign(dFdy(coords.yy)) == half2(1, 1) && sign(dFdy(coords.xy)) == half2(0, 1)) ? colorGreen : colorRed; }