[require] GLSL >= 1.10 [vertex shader] void main() { gl_Position = gl_Vertex; } [fragment shader] #version 120 void main() { float f = 8; gl_FragColor = vec4(0, f/10.0, 0, 0.8); } [test] draw rect -1 -1 2 2 probe all rgba 0 0.8 0 0.8