From: Jorge Valencia Loera (valencia_jorge++at++hotmail.com)
Date: 08/15/2000 08:49:02
Hi Juan,
I used to have the same type of problem with shadows.
I don't know if it's the same bug but I remenber I also had a square of the
same size of the shadow map (256x256 in my case) but it used to be red with
the objects of my scene as seen from the light casting shadows in black! I
remember reading in one of the pf release notes that the red square bug was
not fixed but that it was now black 8-(
(http://techpubs.sgi.com/library/tpl/cgi-bin/getdoc.cgi?coll=0650&db=relnotes&fname=/usr/relnotes/performer_eoe/ch1.z)
:
...
6.3.2 New features in IRIS Performer 2.2.6
6.3.2.1 Multipass Lighting
...
o Prior releases cleared the color buffer to red when
generating the shadow maps for shadow-casting lights.
Code which assumed that the shadowmap generation pass
would clear the framebuffer to black produced incorrect
results, so this behavior has been changed; The color
buffer is now cleared to black when rendering the
shadow map. Note: No assumptions should be made about
the contents of the color buffer between shadowmap and
scene rendering; always clear the color buffer when
unsure of its contents.
...
What happens is that the automatic pass which generates the shadow map is
rendering in the same buffer used to display your first scene (your first
layer) or something like that...
You can do a search for `red square' in the 1999 archives and you'll find
answers to many of your questions. (http://reality.sgi.com/performer)
hope this helps.
-- Jorge Valencia Space Systems Engineer CAE Electronics Ltd. jorgev++at++cae.ca (514) 341-2000 x3733>Hi pfAll, > >I am trying to apply the shadow map capability of Performer to a scene with >heavy use of stencil operations. However, I can separate that part of the >scene and put it in a pfScene, and have another pfScene with the shadow map >stuff (on a separate pfChannel that overlaps). This works when shadow map >is not in operation in the second pfChannel+pfScene. > >Now, I read there is some incompatibility between shadow map shadowing and >stencil operations. I would like to hear a final word on this. I can >foresee some problems if the shadowed geometry is doing incremental changes >to the stencil buffer due to multipass rendering, but in my case my shadow >scene does none of those (no stencil operations at all, but there exists an >8 bit buffer for the first scene). I get a black rectangle on the lower >left area of the common viewport, just like someone else described, where I >can see some hint of what could possibly be the shadow map. > >So, finally, can one use stencil at all when shadow maps are present? >Should I look into some other shadowing algorithm instead? Should I look >further into my own code because it is me screwing it all instead of the >stencil operations or buffer? > >Any hints (or as I said, a final statement on this) would be greatly >appreciated. > >Best pfRegards, >Yuri. > > > > >---- >Por favor, acuse recibo -- Please acknowledge receipt >---- >Juan R. "Yuri" Sáenz-Diez >Vis-Sim & VR Consultant >+34 630 815 772 >jrsdm++at++acm.org >
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