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Lighting with shadows

ZBrush Usage Questions
#1

I’ve read the docs, and spent hours twiddling with the light controls but still do not seem to understand how BPR lighting calculates shadows. Using a Basic Material and a Sun light with shadows enabled, I get a shadow. I also understand that I can go into the BPR render properties and adjust the shadow intensity. That all works just as documented.
What I don’t understand however is this. If I create a shadow as mentioned above, I would expect to be able to put another light in the scene from another direction to soften the shadow. Yet other lights seem to have little effect on shadows cast by other lights. And yet sometimes they do. I have yet to be able to understand exactly what is going on and so far I just seem to “get lucky” after playing with the lights for a few hours to get shadows right.

Anyone understand how to soften shadows from one light by using another light? Or is there a tutorial or documentation somewhere else?

Thanks

#2

Based on my experience, zbrush does shadows in a separate pass and it just overlays it on top of the base render, zbrush has no way of creating soft shadows on only to some parts of the shadow. However, you could do this in Photoshop by using layer masks, painting as white means 100% opacity and black to 0% opacity.

#3

Thanks for your reply. I think you are probably right. After much experimentation it seems that shadows get added on after lighting rather than before. I’ve watched people do amazing things with rendering each light/shadow separately and combining them in Photoshop, though there’s also a reason why Pixologic has teamed up with Keyshot.