CGTalk - getting luminance at point?

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azshall

05-04-2006, 03:32 PM

There is a command called colorAtPoint that does a pretty good job of grabbing the color of a specific point based on an objects proximity. However, is there one for Luminance? I have not been able to find a command to do so, or .. is there a way to get the Luminance value from the RGB value? Better yet, is there a command that will do something similar, like .. luminanceAtPoint ?? (not that I've found in the docs) ...

Also, colorAtPoint only works at the base texture. Meaning, if I try to use a RGB->Luminance utility node through a ramp (like RGB->HSV) and then sample that new ramp, it will not work... It has to be done (from what I've found) at the base texture level as well ...

Thanks

az

pgraham

05-05-2006, 12:47 AM

searching google for "rgb luminance" yields a site withRGB Luminance value = 0.3 R + 0.59 G + 0.11 BThat's the generally accepted weight of the channels in luminance. Just plug your variables into that formula after using colorAtPoint.

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