garageCube

Here is what I have worked out regarding the use of expressions in fixture definitions. Can't work out what COMP represents.

Component types:

• R: red (R)
• G: green (G)
• L: luminance ((0.299 * R) + (0.587 * G) + (0.114 * B))
• W: white (min(R, min(G, B)))
• B: blue (B)
• C: cyan (1 - R)
• M: magenta (1 - G)
• Y: yellow (1 - B)
• Expression: Any GLSL equation with a float result

In addition to R, G, B, L, W, C, M, Y expressions have these variables available:

• (slider name): The value of any slider in your fixture
• INDEX: Pixel index in a multi pixel fixture
• posX: Column index in a multi pixel fixture
• posY: Row index in a multi pixel fixture
• COMP: What is this? It appears to be a value of 2048 in my current setup
• time: time in microseconds

COM is the index of the channel being processed inside the pixel. For instance for a RGB (8 bits per component), COMP will be = 0 for R channel, 1 for G channel, 2 for B channel.