rendering reflections seperate from geometry
by Brock Jolet
on
Apr 13, 2009 at 8:24:46 pm
I am working on trying to composite a helicopter flying past a glass building. I would like to have the reflection of the helicopter on the building as well. I have added a bump map to the building that distorts the reflection to match the distortion of the real footage reflections.
I find that I get the best reflections when I have the building set to black with a transparency of 0% and a reflection of 100%.
The problem I am coming across is that I can't just composite the rendered image into my scene with an 'add' or similar mode because the helicopter is a dark grey and also becomes semi-transparent.
Is there a way to render the building with an alpha channel that knocks out all but the reflection?
Re: rendering reflections seperate from geometry by Eric Chard on May 28, 2009 at 7:46:58 pm
Great question!...(ponders)... I'd look into the OUTPUT SPECIAL BUFFERS plugin (or something like that name)...if there's nothing else in the scene, the helicopter should be the only thing reflected. You might also be able to profitably use UNSEEN BY CAMERA on the helicopter, if you render in passes.
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"Putting the HARM in 'harmonica' since 2005."
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Re: rendering reflections seperate from geometry by Matthew Stewart on Jun 24, 2009 at 12:51:10 am
I would seperate out the major elements. Have the helicopter on one layer, and the reflections on the windows on another layer for compositing. In Lightwave, make two seperate scenes. One with the helicopter and one with the building windows. In the building windows scene, still have the helicopter in it, but in its properties have it set to unseen by camera in the render tab. It will still show up in the reflections.
