hello! thanks for reading...

i've been looking for ways to render groups of objects and then compositing them together in post for animation (moving camera)

for example, render buildings/streets/parking lots... then rendering cars... then rendering foliage... all as PNGs and layering them in post to make the image. this would include masks of other objects that occlude (tree blocking a car for example) the purpose would be to be able to handle large scenes. in my case 700 cars rendering everything yields 2m36s render time, 7GB of memory use, not a problem since i have 12gb vram.

with custom LPE's i can render individual object passes, but the whole scene has to process and render as well...

the iray matte material so far looks like it only works against a background? as opposed to applying it to trees for example that then block out the cars behind the trees.

i definitely understand a limitation coming from the fact that iray is light path based and it needs to account for all light in the scene for reflections/refractions/diffuse etc... so that very well could be the biggest hurdle if not the.

another way of explain this would be a render option like "render subset of scene" camera shader in mentalray.

just wanted to ask to see if there's something i'm not thinking of. thanks.