Integrating 3D models with photography
Interested in integrating your 3D work with the real world? This might help
# 1 09-11-2003 , 06:38 AM
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Join Date: Oct 2003
Location: Ontario, Canada
Posts: 15

Specularity and Global Illumination

I've been experimenting with GI for a little while now in both Maya (using Mental Ray, of course) and Cinema 4D. One thing I've noticed is that GI does not influence the specularity of surfaces at all. This is a major problem because things like waxy leaves, leather, or any other surface that uses specular highlights end up looking like flat solid colour shaders.

I've been trying to think up solutions to this problem, as well as apply solutions others have posted on the various forums I read. One of them suggests using real lights in conjunction with GI surfaces. This does work some of the time, but generally you just get a lot of overexposure, leading to tweaking headaches.

Just a few hours ago I came up with my own solution, which is, as of yet, untested. Anyways, this is my theory so far.

Specularity is actually just a dull reflection. So instead of dealing with specularity maps, create reflection maps and then mute them to whatever degree is necessary.

Of course, this will increase render times, but you'll have specular highlights that are truly acurate. Also, muted and diffused reflections should, if my memory serves me correctly, take less time to render since they don't have to be as precise as sharp reflections. Therefore the rendering hit shouldn't be too drastic. Essentially, you wouldn't be faking specularity, you'd be creating a true simulation of it.

So, if you absolutly need specular highlights with GI, then try switching your specularity maps for muted reflection maps.

Comments are welcome, I'd like to see if people can get some acurate leather, leaves, diffused metal, etc. shaders going using GI that look exactly like their non-GI specular mapped counterparts.

# 2 09-11-2003 , 11:18 AM
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Join Date: Sep 2002
Location: London, UK
Posts: 3,198
You're right. Specularity is kind of like reflection. It is a reflection of the light source itself. One possibility might be (haven't tested) to use the real lights with light linking and emit specular only...

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