reducing colors at render time?

[Hirazi Blue]

For a NPR effect I would want to create some deliberate "color banding", the kind you can achieve in postprocessing using a "reduce colors" operator. Is there a way to tell Mental Ray beforehand to reduce the colors to a minimum, creating the desired "color banding" at render time?

[rray]

I couldn't find anything to reproduce exactly that effect, but you could give a color_curves node a try, inserted between your shader and the material in the rendertree.

Or if you want it as a global effect for the whole rendering, you can also insert the node as a lens shader, between for example an inactive lens effect shader and the camera lend shader port.

But it's difficult to make the curves do the exact stepping effect. It always turns psychedelic.

[Hirazi Blue]

Thanks fpr the suggestion. Which node do you mean exactly?
I am apparently suffering from "node blindness", because I haven't been able to find it yet...
;)

[Hirazi Blue]

i think I have found one possible solution using incidence, a stepped gradient and a toon mixer.

compound.jpg

steppedgradient.jpg

toonmix.jpg

Playing around with the gradient brings even more possibilities, obviously...

stepped.zip

[rray]

I meant "Color Curve" it's giving you a function curve for each channel which you can make "steppy". But using the toon shaders is a much better solution, completely forgot those were there.

[Hirazi Blue]

Was playing with this some more, only to figure out that you could easily plug the stepped compound
between a soft light shader and the light material for a more scene-wide effect...