adaptive dmc question

[emartin8907]

Hi,

I have an interior scene which is very noisy in my raw reflection pass. I am trying to get it clean before starting with the motion blur.

I am trying to optimize my render settings, currently using Adaptive, IR/LC.

When I change my adaptive DMC amount to 0 the raw reflection pass comes out MUCH less noisy!

By changing the amount to 0- am I basically using Fixed Rate sampling?


(The red square is where I region rendered it with dmc amount at 0)


my settings;
min shading rate- 10
adaptive min/ max subDs- 3/100
threshold- .003

AA- area 1.5

Use Local subDs- unchecked

dmc amount- 0

clamp output- On

IR- high- 100/50
LC- 2000, sample size .02

[Morbid Angel]

Sorry what do you mean by dmc amount? There is no such value...Do you mean dmc adaptive amount?

[emartin8907]

Sorry what do you mean by dmc amount? There is no such value...Do you mean dmc adaptive amount?

yes that is what i meant

[Morbid Angel]

Setting it to 0 means vray is not preforming adaptation at all. The reason you are getting nose there is probably because its very very dark in those areas. So the lower the adaptation is the more aggressive vray becomes in the dark areas. I would recommend setting the gamma in the color mapping to 2 or 3, checking for adaptation only, and see if this makes it better.

Try leaving dmc adaptive amount at 0.85 or around 0.6, don't set it lower then that, setting that value too low would force too many samples and make rendering slow.

Lastly, looking at just the reflection layer is not really a proper way of judging the noise. Since the sampling is performed on the rgba image its the total sum of the render elements that result in the clean look, but any given element on its own might look more noisy.

[emartin8907]

Thanks Morbid!

When you say 'checking for adaptation only' where specifically are you talking about?

All the passes are pretty smooth except for the raw reflection, the RGB is showing some noise so I started to focus on trying to smooth out the raw reflection.

I am working in a linear workflow here, gama at 2.2, would setting it to 3 cause problems when I go to comp in Nuke?

[Morbid Angel]

See attached.

When you work in linear those settings have no effect on final output, as the output it self is in linear. But they do have effect on the sampling - which is being performed on the gamma corrected (brighter image) therefor getting more samples in the blacks.

http://joxi.ru/xAev144sYeVePr

[emartin8907]

Thanks Morbid!

That did help but minimally.

Here is my current render I am still not happy with noise on ceiling around the lights and on the hood of the car. Also looks like I'm getting weird aliasing on the lights as they taper off into the background. I think this scene is especially demanding because it's, well, a bunch of long mesh lights inside of a tunnel. fortunately its just a personal project and i have a lot of power to throw at it.




Current settings;
min shading rate- 10
AA- Area 1.5
min/max subds- 3/100
threshold- .005
DMC adaptive amount- .6
Adaptive threshold- .01
Adaptive Samples- 32
Color mapping- Linear, Gamma 3, Don't Affect Colors Only Adptation, Clamp Output On
IR Map- High, 50/25
LC- 1500, sample size .02

here it is with motion blur-

[Morbid Angel]

Yeah so for you to continue now, all you need to do is lower the dmc adaptive threshold, since 0.01 is fairly high so a lot of noise can get skipped. If you measure the values in pixels of the areas where you see more noise, you should see a strong range like very dark and bright pixels (this is what noise is), so the dark pixels if they fall below 0.01 threshold they will get min samples of 3, so if you have a lot of pixels that are lets say for example 0.002 you should lower the thresh quite a bit to clean them up.

Makes sense?

[emartin8907]

Nice, yea it is!

I took it down to .001



It's really close. I just lowered the adaptive threshold to .003 from .005 and that helped a little more. render time went from 8m to 11m



Should I try something other than the adaptive threshold? Should I lower the dmc adaptive amount any lower than .6?

edit- just tried lowering it to .4 it cleaned it up, render time went up to 13 min



then tried lowering the dmc adaptive threshold to .2 and the adaptive threshold back up to .005 I also turned on sub pixel mapping for the aliasing on the lights. render time back to 10m



I think I am pretty happy with this

[Morbid Angel]

Its a weight value between lowering the thresholds and max subdivs in the dmc. Lower threshold will force to use more max subdivs across the image resulting in cleaner render, but higher render time. Its as simple as that

[Intuition]

In this case I'd tune the shaders/lights one by one vs trying to do it all top down. I can never just top/down from the engine level it seems. I'm always checking use local subdivisions because thats the way I learned. Though I've noticed that Vray does its very best to optimize the local subd for a clean image but in this case it may not cut it.

In this case I'd probably tune the reflective shader and mesh light area with the limited region..

The ceiling shader looks like it needs at least 64 subD to clean up. The meshlight probably needs 32-64 subD to clean up. Just tune that ceiling area.

Probably don't need to crush the engine so hard.

Since there is so much reflection you probably could tune it without GI on to save time testing.

min shading rate could be 6
min/max would be 2 / 24.
threshold .007

dmc maybe .750

Then just tune the lights and shaders subD instead of trying to brute force the work at the engine level.