[require] GLSL >= 1.10 [vertex shader] void main() { gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex; } [fragment shader] uniform float one; uniform int count; void main() { vec4 array[8]; array[0] = vec4(0.2, 0, 0, 0) * one; array[1] = vec4(0, 0.2, 0, 0) * one; array[2] = vec4(0, 0, 0.2, 0) * one; array[3] = vec4(0.2, 0.2, 0, 0) * one; array[4] = vec4(0, 0.2, 0.2, 0) * one; array[5] = vec4(0.2, 0, 0.2, 0) * one; array[6] = vec4(0, 0, 0, 0) * one; array[7] = vec4(0.2, 0.2, 0.2, 0) * one; vec4 res = vec4(0); for (int i = 0; i < count; i++) res += array[i]; gl_FragColor = res; } [test] ortho clear color 0.5 0.5 0.5 0.5 clear uniform float one 1 uniform int count 0 draw rect 10 10 10 10 probe rgb 15 15 0 0 0 uniform int count 1 draw rect 30 10 10 10 probe rgb 35 15 0.2 0 0 uniform int count 2 draw rect 50 10 10 10 probe rgb 55 15 0.2 0.2 0 uniform int count 3 draw rect 70 10 10 10 probe rgb 75 15 0.2 0.2 0.2 uniform int count 4 draw rect 90 10 10 10 probe rgb 95 15 0.4 0.4 0.2 uniform int count 5 draw rect 110 10 10 10 probe rgb 115 15 0.4 0.6 0.4 uniform int count 6 draw rect 130 10 10 10 probe rgb 135 15 0.6 0.6 0.6 uniform int count 7 draw rect 150 10 10 10 probe rgb 155 15 0.6 0.6 0.6 uniform int count 8 draw rect 170 10 10 10 probe rgb 175 15 0.8 0.8 0.8