I think the answer lies in the project hierarchy of the scene and the
location of the GI material.
If the illuminated rectangle is in the root level, and the GI material
and all the other objects are in a lower level, I believe the
illuminated rectangle will not contribute to the GI calculations.
Chris M
---------- Forwarded message ----------
From: Henry Tjernlund <[email protected]>
I worked through part of the part of the user manual on NURBS. I go
inspired to make a tea cup, which worked well, BTW. Then I wanted to
render it in global lighting. Attached is a screen capture of the
render in RS 5.
I added a background wall with the "Paper" material and changed the
color to a light lavender. When I render I get a bright hot-spot. It
doesn't show up until the second pass of the processing (which I
assume is the GI post processing.) Lighting is provided by a rectangle
make into a Special-Light. But that doesn't seem to be the cause of
the hot-spot. The hot spot seems to be coming from another rectangle I
am using to get a window-like reflection on the Porcelain material of
the cups. That rectangle has the "Unshaded" material applied to it,
which looks self-luminous. If I had that second rectangle, then the
hot-spot goes away, but so do the nice and interesting reflections in
the cups. I have thought of several ways to try and fix this, but each
takes a while to do test renders. (Just this screen render took almost
3 hours.) So instead of spending days trying a multitude of tests, I
am hoping that the experts here can suggest just the ideal fix.
>>>Mark wrote:
Hi Henry,
I get the problem: because of the global illumination this rectangle
emits light on the environment. It's too realistic ;)
Somehow it has to be excluded from the GI lighting but still be
visible in reflections. I thought it would be trivial, but after some
fiddling around with some old GI projects I can't come up with a quick
fix. I tried shaders which only self-illuminate after one recursion,
but apparently the GI lighting ignores this.
I'm sure it can be done, but somehow either I'm overlooking the
obvious or some seriously deep digging must be done :)
With some tweaking - making use of blurwidth control - your render
times should be more acceptable. V6 largely eliminated problems with
transparent and reflective objects in GI but it's still very slow in
this area...
The only thing I can suggest at the moment is to make a simple room
with a window around the cup, and a large self-illuminating sky sphere
around that. Or a HDR spherical environment. Reflective/refractive
objects always require a decent environment...
good luck,
Mark H
