[require] GLSL >= 1.20 [vertex shader] void main() { gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex; } [fragment shader] void main() { const vec2 v1 = mod(vec2(-3.0, 43.5), vec2(0.9, -4.0)); /* (-0.5, 0.6) */ const vec2 v2 = mod(vec2(0.2, 6.0), 1.3); gl_FragColor = vec4(v1.x + v1.y, v2, 1.0); } [test] draw rect -1 -1 2 2 probe all rgb 0.1 0.2 0.8