Bit of an advanced matte question

[stayinwonderland]

Ok, picture this...

 

I have a scene whereby I want to render out just the foliage onto its own layer in photoshop (for a camera map, so need various elements on their own layer).

 

I choose everything but the plants and go to vray properties, make them a matte and render. All but the plants are black, but all that geometry (in this case the buildings and ground) doesn't register in the alpha channel when saving out a tga.

 

The ground plane intersects the foliage so I can't just have everything be alpha either because you'll see through the floor...

 

 

Any tricks that I can use to basically say - everything I can see should be solid, everything black should be transparent?

 

I tried making the geometry have an alpha contribution of -1 but that didn't work.

[Fooch]

http://www.scriptspot.com/3ds-max/scripts/rendermask

 

Give this a try. You can render a region then mask it out.

 

Or multimatte's

[stayinwonderland]

I'll check that out. One thing I did try was to put a vraylight material override and make all the other geometry a matte in the vray object properties. Make sure to set the material to illuminate on back side too. Then everything is white which can be pasted into a channel in photoshop. But... it's not quite white and certainly not solid/even. So wasn't perfect.