View Full Version : Radiosity Gurus Unite!

Richard Hebert
10-24-2008, 07:17 AM
Is there a technique (map, feature or some obscure unknown family secret) that will allow me to boost a surfaces response to radiosity without raising radiosity levels in general? Here's the case in question. I'm wanting the guns to bounce a little more light to soften some of those dark shadows around them without increasing light levels on everything else. Is this possible with maps?

10-24-2008, 07:33 AM
You might try diffuse maps.

Richard Hebert
10-24-2008, 08:24 AM
Do you know which surface values affect radiosity? Knowing this would give me a great head start without a lot of test rendering just to find out. Sorry, don't have fprime just yet. Looking forward to it in a couple of months though.

10-24-2008, 09:29 AM
Do you know which surface values affect radiosity?

diffuse.... but if those guns are meant to be metal... its not higher diffuse they need its some reflection... and if u want them to bounce light onto nearby surfaces, turn on directional rays.

Richard Hebert
10-24-2008, 11:08 AM
Thanks for the tips. I'll double check the dir. rays and run some tests but I think that may solve the problem.

Captain Obvious
10-24-2008, 12:02 PM
Just fake it.

Richard Hebert
10-24-2008, 12:12 PM
Not that knowledgeable about the software yet. Still getting a handle on surfacing fundamentals and how this software differs from what I'm accustomed to.

Captain Obvious
10-24-2008, 02:43 PM
Ah, right. Well, I suppose you could fake it with lights?

Richard Hebert
10-24-2008, 03:47 PM
Actually, C O, what I'm considering for the moment is to break up the gun's specular highlight with a map. LightWave doesn't appear to do this in a straight forward manner. I rendered these two images in a small 3D app. and simply dropped a photo into the Color channel and the same image into the Specular channel. This is the kind of look that I've been after from LightWave but I can't seem to get the proper channel combination since just putting a map in the specular channel isn't working. Any thoughts on this?

10-25-2008, 02:18 PM
That will work in LW the same way, with the exception that Radiosity does not affect any Specular at all. Specular is purely a response to cg lights, it was created to fake what you can get with HDRs. You need to use blurry reflection instead. You'll find this in the Environment tab of the surface editor.

In order for your color map to affect the reflection color, you need to turn on Color Highlights in the advance tab of the surface editor. This takes color from the map in the color channel and multiplies it by the reflected color. Color Highlights works with Specularity too, if you have cg lights in the scene.

Richard Hebert
10-25-2008, 02:37 PM
Actually, I've tracked it down to the Surface Editor window. When I attach maps to the specular channel in that window I do not get the results that I'm after. However, when I attach the same maps in the same manner in the Node Editor I get results equivalent to the posted images. Any thoughts on how or why these two windows behave differently? This info. will help me determine which one to use to get appropriate results.

10-25-2008, 04:58 PM
They should act the same way. Are you sure you set everything correctly?

Richard Hebert
10-25-2008, 05:42 PM
Everything is basic and straightforward. Just an image plugged into the color channel and that same image plugged into specular channel. Setup is the same in both windows. Nothing else is altered but different render results.

10-25-2008, 05:47 PM
Can you post your object?

Richard Hebert
10-26-2008, 07:50 AM
Here's a Specular test file. The two renders are from the Surface Editor and Node Editor respectively. I'm noticing that the render from the Node Editor has more pronounced contrast even though the two renders are from the exact same map. If I'm overlooking or misunderstanding something (highly possible) please let me know. Thanks for any insight.

10-26-2008, 02:47 PM
What you're doing differently in the nodes is plugging the Luma into the Specular instead of the Color. When you plug the map color into both spec and color channels it renders the same as when using the surface editor method. I think the luminance of a color is different than just making it greyscale, which is what LW does when you put a color map into spec.

It's totally up to you which method you use, use what you think looks best. Personally I like the more contrasty looking one - the Luma version

Richard Hebert
10-26-2008, 03:09 PM
Thanks for the insight. I overlooked that and I did believe that the luma was only greyscale. I prefer the contrasty look also, thanks for the clarification!