Isolating reflections

[golly]

Is there any way to make a reflective matte object?

I want to isolate a reflection with it's own alpha channel.

Similar to casting a shadow on a matte object and getting alpha channel info where the shadow has fallen.

I'm integrating some CG into live action, and the comp artist wants a reflection in a window, but only wants what's reflected...no background plate information. (apparently so they can change the back plate during comp)

Is there a way, and if so, how do I do it?

[DP]

in one pass...not that we have found

however...render one pass with reflection at 100%, one at 0%, then build a mask with all objects apart from the reflections 100% self illuminated black, the reflective objects 100% self illuminated white, and render that.
This will build the alpha for the reflections which you can drop into the reflections and adjust transparency to suit....

or course, if you have relfective objects with varying reflection values you need an alpha pass for each different reflection opacity.

[golly]

Yeah thanks, looks like that 100% black thing is only my option.

I played around so so so much with the materiel wrapper, EVERY damn permutation of that and alpha etc but no luck.

It should be implemented in the wrapper material ....Reflection affects alpha on/off option.

But it ain't.

yet.

cheese
James[/img]