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bbuxton
06-01-2006, 11:44 AM
Is it possible to control caustics with separate IOR values for R, G & B colour channels? This would save me a bundle of time in post, not to mention render times. Any tips on how to do this using the node editor would be great!

BB

nlightuk
06-19-2006, 02:55 AM
AFAIK, there's no way to do this with the node editor at this time, because none of the nodes allow separate R, G, and B channel output.

I am not entirely sure how you would use the information, and why it would save time, but if someone were to write a node that did the above, then you could easily set up a gradient or some logic nodes to apply different IOR values based on the channel values coming from the colour of the surface.

GregMalick
07-13-2006, 12:08 PM
You could split the color into its components using 3 instances of the "Color Scalar" node. You'll find it under the Tools group. Double-click on each and set the Mode to the Color Channel you want to split-out/modify.

If you need to bring them back together as a color - use the Make Color node.


Yikes - i notice you are talking about controlling caustics. So splitting is not a problem - but controlling caustics would be. There is no access to Global Illumination's Caustic Intensity/Accuracy/Softnesss that I'm aware of.

Sande
07-13-2006, 12:39 PM
bbuxton: Would this prism tutorial (http://lw-fin.org/tutorials/asa/prisma/tutorial_prisma.html) help you?

Captain Obvious
07-16-2006, 02:23 PM
Nitisara has developed a shader that does chromatic abberation:

http://www.newtek.com/forums/showthread.php?t=42148&highlight=prismatic

bbuxton
07-19-2006, 05:51 AM
Nitisara has developed a shader that does chromatic abberation:

http://www.newtek.com/forums/showthread.php?t=42148&highlight=prismatic

The Prism shader is fantastic!
I originally posted the question before the shader was ported to Mac.

For those interested, say if you're using fPrime and can't use the shader - the long winded approach.....

Make three renders, one for each colour channel. You should change the refraction index by a very small amount for each render, say +-0.02. You then combine the appropriate channel from each render in your compositing app or image editor. Result, nice rainbow caustics.

Regards
BB

Captain Obvious
07-19-2006, 06:46 AM
A better way than that, bbuxton, is to animate the index of refraction and transparency color, and use motion blur. :)