CGTalk - Problem: Showing light on Matte/Shadow object

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ciscocd1

04-02-2007, 09:03 PM

I'm working on a car crash animation in 3D Studio Max 8/ Mental Ray:

I'm using a nighttime spherical panorama of the crash scene as the background (self illumination at 75%) for the animation.
I have the 3D terrain of the scene from a digital survey which I've applied a matte/shadow material and the car casts shadows on the "road".
The 3D camera is locked down and can pan the environment. (following the car down the road)
It looks beautiful- lighting , shadows glow/glare on the cars lights (thanks Jeff Patton for the glow tutorial) I have spotlights attached to the front of the car for headlights.
How do I show the headlights illuminating the matte/shadow "road"? Is there a workaround with a render pass? I am stuck!

Any suggestion would be appreciated.

scrimski

04-02-2007, 09:43 PM

I don't think this is possible with a Matte/shadow-material. I would try using a standard white material with a Light/Shadow falloff in the opacity and maybe in the Specularity and Glossiness slots. Lit would be set to white, shadow to black. Didn't tried that out, just an idea.

ciscocd1

04-03-2007, 03:27 AM

Danke, Scrimski,
I tried your idea and its a decent workaround. Here's what I did:

rendered a regular frame and a Material Override frame with the Shadow/Light Falloff
took both to Photoshop. Desaturated the Shadow/Light image.
layered the Shadow/Light over the regular frame and set the blending mode to "color burn". Flattened the image.
layered the Flattened image over another regular frame and set the blending mode to "screen"
I'll try a short clip next and try the same in Premiere.
Thanks for your help.

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