XM Magdalena 3D print, GGeorgy (3D)
LC #42 Pipers Alley

View Full Version : Caustic coloring in XSI

06-03-2006, 09:47 PM
I was considering having a go with XSI at the glass render challenge here:


I wanted to try using different colored glass like I did with Cinema 4D in the image below, with caustics, but it appears that you can't actually make the diffuse color or the transparency color of an object drive the color of the caustic in XSI. You can set the photon color mode in the light, but that is light specific and not object specific. You can set a color multiplier for the scene in render settings, but that is neither light nor object specific. Is there a way to have one light produce two different colored caustic results for two different colored objects?

Another question I have on caustics. I don't think XSI makes a distinction between bounced caustics and pass-through transparency caustics. Correct? So there is no way to adjust these values independently. For example, in real life, the intensity of bounced caustics depend on the reflectiveness of an object, while the pass-through caustics depend on the degree of transparency. It would be helpful if I could adjust them separately. Thanks.


06-03-2006, 11:19 PM
To answer half my own question, I figured out that caustics color and intensity is driven by the specular channel values, even if specular is inactive. I guess that's one small step for a man, one giant yawn for mankind. :)

06-03-2006, 11:36 PM
Michael, just plug a photon shader in your material photon port.
there's a transparent slot you can use to drive caustic colors,
independently by the obj transparency. but take care that
actually the transparent slot in ie a phong drives also the caustic
color.. is that sometimes the caustic efx is too strong and blow
out to a white color.


06-04-2006, 12:00 AM
Thanks francescaluce. Another clue. :) When I try that, the color of the bounced light is inverted. Any ideas about that?

06-04-2006, 12:43 AM
what ya mean by 'the color of the bounced light' ? :rolleyes:


06-04-2006, 01:15 AM
Maybe this explains better. The top image is using the specular color to drive the caustic color. The bottom image uses the Photon node you suggested with a green gradient plugged into the transparency channel. Oddly, the color of the bounced light is this time inverted.



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