CGTalk - Casting reflections with Matte/Shadow Objects

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rkgibbons

05-20-2003, 06:56 PM

Hi guys,

Over the weekend I was lucky enough to view a demo of RealViz's "MatchMover Pro" software. I was blown away by the power of this software in its ability to match 3D camera motion with live footage (but unfortunately, I was also blown away by the price!)

Nevertheless, When I arrived home I started doing some experiments with compositing 3D objects into video footage. I started with a simple video consisting of a computer desk cluttered with a variety of objects. With this, I managed to successfully match the 3D camera to the real camera.

At this point, I placed a 3D teapot on the "surface" of the desk. To mimic the reflective qualities and shadow-receiving characteristics of the desk surface, I created a box and applied a matte/shadow material to it.

The virtual desk successfully reflected the teapot and composited well within the live footage.

But now I would like to have the teapot reflect the desk surface as well.

Is there a way to somehow apply another material to the shadow/matte object (the 3d desktop) and have the teapot reflect this surface -- without rendering the surface?

I've tried to use the video footage as an environment reflection on the teapot material, but this looks like crap. It doesn't really mimic real world reflections.

Thanks for any tips!

Keith.

nimajneb

05-20-2003, 07:06 PM

My advice would be to make a rough model of the desk and room, then create a cube map from the point of view of the teapot. This you could then layer on as a reflection map, masked for falloff and blurred. It may give you the effect you're looking for, and would require no extra geometry in the render for composite. If you render to layers, that reflection should come out separate and you can tweak it's color to better match the surroundings as well. Remember, it doesn't have to be perfect. If you assume that your object is not mirror perfect chrome, the subtle shapes of color the fake map makes will carry the illusion. If you want an exact reflection however, then I'd say you're shafted. More experienced folks in the compositing forum may have ideas for you.

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