#version 120 varying vec4 var0; varying vec4 var1; void main() { gl_FragColor = vec4(gl_PointCoord.xy * 1.1 - 0.05, 0, 0); if (var0 != vec4(0, 1, 2, 3) || var1 != vec4(4, 5, 6, 7)) gl_FragColor.z = 1; /* something is wrong */ }