Vray noise in glossy reflections help

[stevejones]

Hi All.

 

I have been doing some renders of this car I've been modeling, and I'm working on some detail shots of the wheels, but I'm getting really bad noise in the glossy reflections of the rims. Here are some examples

http://i.imgur.com/5Th5vAo.png

Here is a render

http://i.imgur.com/H997NZx.png

here is the rawreflection pass. This is the only pass that has the noise, so I know it's a reflection problem.

http://i.imgur.com/45dLZZ0.jpg

Here is the sample rate

I also did a test of more generic objects to see what's going on:

http://i.imgur.com/BqGFrEi.jpg

some shapes, no noise.

http://i.imgur.com/1sP90Ns.jpg

reflection pass

http://i.imgur.com/GORJA5U.jpg

samplerate

 

 

As you can see, the generic objects are fine, but the rims get a lot of noise, and in very specific areas, and for some reason those areas are not getting enough rays. My only thought could be that those areas might be ones where secondary rays are doing a lot of bounces back and forth between the object itself.

 

The settings for the render of the tire was using universal settings and took about 48 hours. I cranked the subdivs of the material up to 512 and that didn't make much difference.

 

I did a lot of research on mental ray and the Adaptive DMC sampler, so I know how that works, so I thought I'd try the other approach and lower the image sampler from max 128 to max 8, 16, 32, and 64, while upping the glossy subdivs to 64,128, 256, and 512. I also tried upping the lights to 64, 128, and 512. In most of these cases the results were even worse than the universal settings, but they at least were much faster. I even tried setting the max depth of the glossy material to 1 and as high as 512. No matter what I try I am consistently getting noise in those areas and cannot fix it. After doing that test it seems like it must be something to do with the complexity of the object, but I cannot figure out how to solve this problem. Any help or advice would be greatly appreciated.

[jasonstewart]

Please post up some screenshots of all your settings (vray settings, material settings, and light settings). Its hard to track down without knowing those things.

 

Also, have you tried overriding your materials with a flat (as in no reflection, bump, etc) gray material to verify that the geometry is in fact good? Sometimes overlapping geometry can cause issues like this. That is the first step I would recommend.

 

To me it looks almost like your bump map (I assume you have one on there) is too strong and you are getting the "noise" because it is only noticeable at almost parallel angles (that seems to be the only place it is happening and with fresnel enabled the material is more reflective at closer to parallel angles).

Edited March 9, 2014 by jasonstewart

[himanshuchoudhary]

Have you tried increasing the subdivisions on the reflection map settings?

±This might reduce the noise a lot. As Jason says, it would be good to see all your settings...

[stevejones]

Here are sort of the "baseline settings" I used

Material:

http://i.imgur.com/AlX2HVl.jpg

Vray:

http://i.imgur.com/ExVFGYi.jpg

Indirect Illumination:

http://i.imgur.com/1tYkn1m.jpg

Settings:

http://i.imgur.com/ihvboXb.jpg

 

As I mentioned I did rensers with a variety of settings based off this, upping the material subdivs to as high as 512, and I still got the noise. I also used "Universal Settings" With Adaptive DMC Image Sampler max divs up to 128.

 

I thought it might be the geometry as well, so I did do a test render with a basic material and it looked fine. I checked it for double faces, and there were none. I exported it to .3ds, reimported it, and did a reset x-form. Same results.

 

I actually managed to solve this problem, after tonnes of searching I found another thread with this problem. There were a ton of solutions provided, and one worked for me: Under Material "options" I set the "Treat glossy rays as GI" to "Always" This fixed the issue. I would however, like to know exactly what this does. I looked it up in the vray documentation, but it doesn't say much about it, other than the glossy rays will be handled by the secondary gi engine, which can be a lot faster.

 

Thank you very much for your replies, and if you have any other suggestions I'd be happy to hear. Sorry I did not post my solution, I missed the notification that this post was live.

[Tze Czia Ti]

hi, I'm having this problem, noise on glossy reflection, and there is no 'treat glossy rays as GI' setting