View Full Version : Reflected RGB Matte Pass... Is it possible?

12-06-2011, 01:49 PM
I have a shot where I'm creating a CG reflection on a car's windshield driving through a tunnel-style bridge with lots of lights illuminating the surfaces of the bridge. This CG reflection will then be comped onto a green screen shot of two guys in a car.

I've modeled the tunnel and windshield out and am shooting the entire shot right on the windshield, meaning, everything in the final beauty render is a reflection ON my CG windshield object. I'm doing this to get the warps/angles of the bridge geometry and its lights as the windshield "drives" through the tunnel.

Now I wanna do an RGB matte pass of my my bridge geometry, my light-fixture models, and the light poles for comping. I do this by using DP's Pixel Node Filter and DB&W's Filter node to choose the objects, pass them into a Make Color node, then send this to a buffer and kick it out in exrTrader (a workflow that has worked great in the past).

My problem is when I setup the RGB pass, I can color my objects, but anyway I set up the pass, it wants to "color" the windshield as well versus letting the colored objects reflect through it as normal. Is there any node combination/way to setup a buffer that colors objects but doesn't color the object you want to reflect the other objects?

I know I can do this by creating "matte versions" of all the objects except the windshield and then just render an additional scene with my matte objects on my windshield, but the point is to avoid this and use a smarter, more modern workflow in LW.

12-06-2011, 01:54 PM
Hm, I think there'd be a way to set up a node workflow using shaderMeister (since, as oppose to the DPFilter node, it affects the surfacing).
Probably not in a single pass render... but without the need to a different set of objects.


12-07-2011, 12:24 PM
Ah, forgot I could use ShaderMeister to at least keep it in the same scene. It definitely seems like a surface-shading override type of situation. I was trying to rack my brain if there would be some way to use logic nodes to blend the beauty render with the RGB matte render in the Pixel Filter or Image Filter.