If I want to render the monkey reflected in a mirror - but I want the background reflected behind the monkey to be transparent with alpha 0 (so that I can composite a different background into the blue area of the shot later on without having to Chroma Key it).
How would I go about doing this?
I know the blue is from the background reflected in the mirror. What I’ve done before in a previous film is - like you’ve mentioned - put a cube or plane with UV mapped background on it, directly behind the character/monkey head so that the mirror reflects that. I could’ve also chroma keyed the blue section and composited in whatever I need.
But what I’d really like to find out if it’s possible to make the reflected part totally transparent? Is it impossible?
With raytracing and mirrors, i remember something about increasing the bounce factor from the default 2 so that the photons properly are mapped. BUT, as said above, the blue is from your world; delete your world if you dont want it.