[require] GLSL >= 1.10 [vertex shader] void main() { gl_Position = gl_Vertex; } [fragment shader] uniform vec4 color; void main() { vec4 c = color; if (color.x < 1.0) { c *= 2.0; } gl_FragColor = c; } [test] uniform vec4 color 0.0 0.5 0.0 0.0 draw rect -1 -1 2 2 probe all rgba 0.0 1.0 0.0 0.0