dmc sampler: per object settings possible?

[flipside]

Hi,

I am rendering a few objects in a clean white environment, lit by vraylights. All is fine, but now I need to render the same thing, but in a dark environment. The floor/background objects simply changes from white to dark green.

This introduces tons of noise in the shadows on the floor. Reducing the adaptive amount in the vray dmc sampler from 0.85 to 0.2 is the only thing that really helps, but this doubles the rendertime.

So I was wondering if there is a way to tell vray to only use this low adaptive amount on the floor object, and the 0.85 setting on everything else?
(I would prefer not having to split the render in 2 passes)

I can also increase the light subdivs a lot, but this also affects the shadows on lighter objects that don't need better sampling.

Any help/tips are welcome

Cheers,

Wouter

[joconnell]

Hmm - what's the material on the floor? There's no current option for per object dmc but it is being worked on. If your lights are causing the noise I'd be more inclined to up them and back off your DMC to be honest!

[flipside]

It's a simple vray material, only diffuse, no reflections or anything. I did some testing and increasing light subdivs increases rendertimes much more to get the same level of noise as with changing the adaptive dmc setting.

A combination of lower noise threshold and lower adaptive amount currently gives me best results, still longer rendertime but I think it might be acceptable for this job.

Thanks for the reply!

[joconnell]

I'm curious about this - what aa settings?

[flipside]

I always use adaptive DMC AA sampler with default settings (so it uses vray dmc sampler noise threshold).
Then vray dmc sampler set to adaptive amount 0.85, min subdivs default, noise th 0.01 and global subdivs multiplier 1.0

I always increase glossies, area shadows etc in the scene to at least 16 subdivs. (instead of using global subdiv multiplier as this also affects ir map calculations and other stuff)

Now with the dark floor, I need to use adaptive amount 0.6 and noise threshold 0.002 to get low enough noise (similar to 0.85 + 0.01 with white floor).

In fact I always have this problem with darker floors, but usually for stills it doesn't matter if a render takes 20 or 30 minutes

[joconnell]

Hmm - upping the adaptive amount and lowering the noise threshold seems a harsh way to solve the lighting problem, but as your scene has nothing but lighting in it maybe it's okay

[Dariusz Makowski (Dadal)]

There were plans to put a per object DMC sampler but not sure when will they hit our versions...

[3DMK]

There were plans to put a per object DMC sampler but not sure when will they hit our versions...

Lets hope this happens as Per-Object/material control of AA will be an awesome addition.....just like the per-object GI subdivision that was implemented in Vray 2.0 was.

[zoranm]

One trick I use is to introduce a new light to directly lit those dark corners/objects(which mostly receive secondary bounce). Set the amount to a tiny value (like 0.1) and exclude everything else. This seams to help DMC to have "more matrial"/samples to work with, thus reducing noise.

Hope this might help

Zoran

[joconnell]

You could probably add in a vray extra tex element with a selection set for only the noisy objects, and turn on "consider for anti aliasing" to force vray to give it extra samples too.

[Dariusz Makowski (Dadal)]

So you use it as sort of ambient light to increase overall brightness of dark spots.. interesting... Might do it on my projects too since then I can just tweak it back using levels in PS...humh...

Thanks!