Reflection Pass -

12) It may be that you have some objects in your scene that will reflect your CG object. You'll need to make these objects as match moves just as you would for shadows. Assign a material to these reflection match moves and make it fully reflective.

13) Now simply select your CG object and choose info -> selection -> Render set-up and turn off Primary rays and keep Secondary rays turned on. When you render with Mental Ray you should now find that your CG object won't render but it will render as a reflection in your match move objects.

14) Another option would be to make all your match move objects constant black, then when you render out the reflection pass your CG object reflection will be masked if required. In my example the balls reflection must seem to appear from behind the reflections of the walls I can simulate this with constant black match move objects which would mask the balls reflection correctly (assuming all the lights and cameras were positioned correctly !).

15) You can place your reflection pass into your composite in exactly the same way as you would with the shadow pass.

Now you can put it all together using your compositing software (I tend to use AfterEffects), remember to add some noise and blur, and perhaps desaturate your RGB layer a little.

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A native of Britain living in Singapore, Ben Cowell works with 3D Studio MAX, Softimage|3D, PhotoShop and Aftereffects. He has Lectured in Animation and Special Effects at Temasek Polytechnic Singapore, teaching the 3D animation and effects course at the Polytechnic. He is also programming director for the Singapore Animation Fiesta. Check out his website at http://www.rethinkfx.com.

 

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