Rendering in Layers for Compositing / Memory usage

bwise1701

Is it possible to render elements of a scene - a character or characters and the background independantly with Alpha channels such that they can be composited together foir the final image. I have some scenes where I have 5 figures in an indoor scene and it's exceeding my Titan's 12GB memory and falling back to the CPU - I'd rather not wait overnight for a decent render. 

 

Thanks

TheKD

Yeah, it is possible, but if you have an eagle eye, sometimes it just don't look right, even if you can't put a finger on why lol. The way I used to do it, I would break up the render into a few passes, based on distance from the camera. First pass, I would only render the HDRI if I was ising one as a backround. Second pass would be everything in the far distance behind the focal point. Then a pass for the focal point distance, then one for foreground elements etc.

For all the passes after the HDRI pass, in the render tab, environment section, turn draw dome and draw ground off. When you save the image, use a format that supports alpha like PNG or TIFF.

bwise1701

If I render foreground elements with the set not visible - how would I get the right lighitng on the foreground elements ?

TheKD

I think that is one of the things that made it look wrong to me. Things like missing shadows are not super hard to fix, but missing light bounces and such, I am just not that good lol.

3141592654

Here should be some encouragment ... back when I only had a laptop with a 960m graphics card I made this. It took 8 separate renders which were later composited.  The empty classroom was the base, several props were a pass, each row of students were a separate pass, the teachers desk was a pass, and the final pass was for the floor shadows made specifically by having all the desks in the classroom without the students. I have since gotten a machine with more memory and a better graphics card and can just barely do the whole thing in one render - and it is fairly close to correct - the shadows are a little different, but it is so busy it is not something one notices quickly. I was careful to assemble each of the sections to render in the correct place and I used the same lighting in every render to be consistent. Since this is all contained in a room, the lighting could be consistent. I do not know what your scene includes so I cannot guess how to adjust your lighting.