Separatig the fog from the other elements

[jstrob]

When we render a scene with fog and separate it in elements, the fog gets in all element which is very unpracticall cause if we want to tweak the fog separatly (which is the whole idea of rendering in elements) we have to render everything 2 times, one time without fog and another time with fog and every object in mattes which double the rendering time!

Wouldn't be possible to consider the fog as a separate element so it would be excluded from the diffuse and occlusion and every other element except vrayAtmosphere? I have a render taking a week, so I would save another full week if vray could do that!

Thanks.

[kimgar]

for z and ao at least, you can turn off filtering, see thread here :
http://www.chaosgroup.com/forums/vbu...nvironment+fog

[joconnell]

Also adaptive subdivision can really cut down your render times if you do a separate pass with your objects as matte objects for the fog, and use an extratex element for the ao - much quicker render times.

[jstrob]

But if I want to have a beauty pass without fog, then a pass with the fog, and not turning off filtering... I am forced to render 2 times the whole thing. And when I need displacement to mask the fog, it is 2 times longer to render. But I guess that it is possible mathematically to render everything in one go with cleanly separated elements? Why not?

[Seraph135]

+1

I would really like to have this too.

Tim J

[Dariusz Makowski (Dadal)]

Assuming ur displacements are done in vraymoddisplacement and not via shader then u can do this:

F10 vray general
Override shader > set it to vraylight with 0 in power
Set Adaptive subdivision at 0/0
Set up ur fog
Disble all lights and so on.

Render - it will take like 2 min to render it...

if u use displacement from shader, then just disable all texture filterings, lights, etc etc in ur scene, set raytrance bounce to 1 no GI etc etc and render it again, Should render it in few mins too...

[Morbid Angel]

I understand what you are looking for. But what would be the idea behind getting the fog out of cg, vs the fog generated in comp?

[Seraph135]

I understand what you are looking for. But what would be the idea behind getting the fog out of cg, vs the fog generated in comp?

I'm pretty sure strob and I are both referring to getting environment fog into a buffer by itself but also being able to assemble all the other buffers to rebuild a beauty render that looks as though the fog was never there. I would imagine this is possible but it's probably very involved. Since fog could be seen in reflections and refration and also disperses the lighting it may be more trouble than it's worth. Currently it seems that even if you render all your buffers with the fog on in a single pass you still can't comp everything back together properly because there isn't a fog depth buffer to use as its alpha.

Tim J

[vlado]

It might be possible to exclude the fog from the elements; since we will also be adding an atmosphere alpha element, it should be possible to get this done in one render pass.

Best regards,
Vlado