 | | | Bump shading anomaly | Bump shading anomaly 2004-02-19 - By Morten Bartholdy
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Hi list,
I stumbled over this one because I worked on very high factor values for bumps
- check this image:
http://colorshopvfx.dk/XSI/bump_shading.jpg
Notice the jagged shaded polygon edges where the arrows point. It looks like
the old Softimage renderer problem with raytraced shadows - here it is like the
shading is not smoothed when normals are pertubed by a bumpmap.
There is one pointlight in the scene with raytraced shadow and no area - area
lights will smoothen the problem areas but it is still there.
Obviously the jaggies correspond directly to edges so upping the SubD helps,
but still leaves the very hard edge between lit and shadow area. This kan then
be helped by using big area lights, but it sort of defeats the idea of
optimizing a scene for rendering.
It is not an on/off problem when the factor goes beyond a certain value - it is
just not very visible with low values, and certain types of bumpmaps don't show
it much either, which is why I have not seen it before.
Do anyone here know a workaround - a clever Rendertree solution to smoothing
the shading or is this one for support?
TIA!
Best Regards
Morten Bartholdy
3D Animator & Visual Effects Supervisor
Colorshop VFX
Denmark
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<DIV><FONT face=Arial size=2>Hi list,</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I stumbled over this one because I worked on very
high factor values for bumps - check this image:</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2><A
href="http://colorshopvfx.dk/XSI/bump_shading.jpg">http://colorshopvfx.dk/XSI
/bump_shading.jpg</A></FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Notice the jagged shaded polygon edges where the
arrows point. It looks like the old Softimage renderer problem with raytraced
shadows - here it is like the shading is not smoothed when normals are pertubed
by a bumpmap.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>There is one pointlight in the scene with
raytraced
shadow and no area - area lights will smoothen the problem areas but it is
still
there.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Obviously the jaggies correspond directly to edges
so upping the SubD helps, but still leaves the very hard edge between lit and
shadow area. This kan then be helped by using big area lights, but it sort of
defeats the idea of optimizing a scene for rendering.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>It is not an on/off problem when the factor goes
beyond a certain value - it is just not very visible with low values, and
certain types of bumpmaps don't show it much either, which is why I have not
seen it before.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Do anyone here know a workaround - a clever
Rendertree solution to smoothing the shading or is this one for
support?</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>TIA!</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Best Regards</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>Morten Bartholdy<BR>3D Animator & Visual
Effects Supervisor<BR>Colorshop VFX<BR>Denmark</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV></BODY></HTML>
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