[require] GLSL >= 1.20 [vertex shader] void main() { gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex; } [fragment shader] void main() { const vec3 signs = sign(vec3(0.0, -42.9, 55.7)); const float one = float(signs.x == signs.y + signs.z); gl_FragColor = vec4(0.0, one, 0.0, one); } [test] draw rect -1 -1 2 2 probe all rgb 0.0 1.0 0.0