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View Full Version : separate shadow pass in translucent scene?



rexguo
02-26-2010, 11:27 PM
Is it possible to implement separate shadow passes
in scenes that are heavy on translucent geometry?
I would think not since it is not possible to 'insert'
a shadow between 2 polygons that have already been
alpha-blended. I'd love to be corrected though, since
separate passes allow simpler shader setups.

dletozeun
02-27-2010, 03:50 AM
For translucent geometry you need an additionnal pass to make it cast shadows because depth writing is not enabled during rendering.
In the shadow pass you can simply process translucent geometry as opaque geometry first. If you want colored shadows, it is quite more complicated as you also need a color information. But I think there are some papers talking about this problem.

Alpha blending operates after fragment shading, so you can process shadows on translucent geometry first in the fragment shader.

rexguo
02-27-2010, 04:28 AM
Thanks, dletozeun.

So far everyone I've asked says MRT + depth peeling
is the only way if the goal is to 'defer' applying
shadows (not rendering the depth map) in its own pass
(after the usual geometry pass).