[require] GLSL >= 1.10 [vertex shader] void main() { gl_Position = gl_Vertex; } [fragment shader] uniform float v; void main(void) { gl_FragColor = vec4(1.0) / v; } [test] uniform float v 2.0 draw rect -1 -1 2 2 probe all rgba 0.5 0.5 0.5 0.5