Noise Reduction Help

[bmcgonigle]

Hi, very new to VRay and I'm hoping I can get some help in resolving my noise issue before I rip what little hair I have left out. I've been self teaching (I also took Brian Smiths VRay class set; VERY helpful and well done!) and doing what tutorials I can find but can't seem to shake the noise from my images.

 

I've got a scene that i created in a studio format (wrap around plane for the set, vray lights from left, right, front and top) with a common model I work with. The light levels are good but I can't seem to tweak my settings enough to get rid of the noise even when rendering at med to high settings. Any help would be appreciated

 

 

[Stephen Thomas]

I think your max subdivisions are holding you back in your qmc settings. You can lower your noise threshold as much as you like, but it will only subdivide up to your maximum level then stop. Try changing your min to 3 and your max to 6. I'm sure Brian would also agree with keeping your Hsph. Subdivs. down to 20 in your Irradiance map settings too.

 

Changing your gamma to 2.2 in your color mapping and checking the adaption only button will help out with noise in your shadow areas too.

[bmcgonigle]

Stef, thanks very much for help. I made your recommended changes and the noise was reduced but still somewhat visable. I took it upon myself to try and tweak some things to see if I could improve the noise issue further on my own. If you wouldn't, please take a look at what changes I madea and let me know what you think.

 

QMC image sampler 3/12

noise threshold .003 min Samples 11

 

Now for a few questions.

 

Would increasing the secondary bounces in QMC GI help with the noise in the deeper corners?

 

I was a bit unsure where to make the gamma color change. I made the change in my color mapping rollout and check off the adaption only but I also made the change in my preferences settings. I set the gamma to 2.2 and the output to 2.2 as well. Is that correct?

 

This is the current view of the scene; it appears to me that most of the noise is gone but then again my eyes are not as young as they used to be

 

[Stephen Thomas]

Regarding your lighting setup, why not just use the environment override in your render settings rather than your 5 vray lights? Seems like this would be a lot easier.

 

I was referring to the gamma part of your linear colour mapping settings. As for your preferences you want your gamma set to 2.2, your input set to 2.2 (for when you start applying bitmap textures) and your output gamma dependant on how you save your renders; 1.0 for 32-bit image (.exr or .hdr) or 2.2 for 8-bit images (jpeg, targa, tif etc.).

 

If your using a skylight then you can get away with less bounces as light is coming from all angles. Bounces are more important for interior scenes when Light Cache is more efficient than the QMC system. Noise issues tend to come down to your image sampler settings being to low, but I don't think you need to go any higher than you are now.

 

Chris Nichols suggests a good starting point as being min=1 max=16 color threshold=0.01 in his gnomon tutorial on image sampling. However from what I've read of Brian Smith's tutorials I think he would suggest that for most scenes you dont want to separate the min and max by more than 3, and that 3 and 6 are good starting values. I've got away with using 2 and 5 before, but it depends on the scene and remember that once you have a more complex scene with many light sources, textures and blurry reflections, these settings are going to have a big impact on your render times, so start off conservatively and increase a little if need be.

 

Good luck!

[Brian Smith]

Brian,

I'm like 95% certain that your noise is a result of the low qmc subdiv value...for your GI QMC. You can set your QMC Noise sampler to 0.0 and it wont make a lick of difference if your QMC GI isn't taking enough samples. If you increase it to 20, you will see a substantial reduction in the noise...but values closer to 40 might be needed to remove the noise completely. If you still have noise after increasing the QMC GI sampling, then it's not your GI...it's your image sampling.

 

As far as image sampling min/max values, just understand that the same thing holds true. You can set your Clr threshold to 0.0 and if you dont conduct enough samples, i.e. if your Max rate isnt high enough, you'll still have noise. In fact, if you set Clr threshold to 0.0 (or leave the sampler tied to the Noise threshold value), then your Adaptive QMC is no longer adaptive. The reason is that if you set it to 0.0, you are telling the image sampler that you want a perfect sampling solution, and it will use the Max rate everywhere in your scene, and not even waste it's time with the insufficient Min rate.

[pyang]

try this:

min -5

max -4

 

hsph subdivs 100

interp. samples 50

 

noise theshold 0.002

 

should be very smooth.

 

FYI: loss of detail if you have complicated maps, bumps.

 

 

 

Hi, very new to VRay and I'm hoping I can get some help in resolving my noise issue before I rip what little hair I have left out. I've been self teaching (I also took Brian Smiths VRay class set; VERY helpful and well done!) and doing what tutorials I can find but can't seem to shake the noise from my images.

 

I've got a scene that i created in a studio format (wrap around plane for the set, vray lights from left, right, front and top) with a common model I work with. The light levels are good but I can't seem to tweak my settings enough to get rid of the noise even when rendering at med to high settings. Any help would be appreciated

 

 

[bmcgonigle]

Stef, thanks for the clarification on the gamma. I use a few different lights so that i can adjust levles and colors for some dramatics. Being office furniture it needs all the help it can get

 

Brian, I made the changes that you suggested in regards to the QMC GI and there really was no major change. I went ahead and made a few tweaks to the QMC Sampler and although not 100% it does look a bit less noisy. The main area of the noise is under the horizontal surfaces.

 

I've got things set as follows, take a look and let me know where I can make some more tweaks to kill the noise monster

 

QMC Adaptive Sampler: 3/12

QMC GI: Subdiv 40 Secondary Bounces 3

QMC Sampler: Adaptive amount .85 Noise Threshold .003 (won't go any lower) Min Samples 11

 

Any thoughts are greatly appreciated and thanks for reviewing the min/max sampling process. There seems to be alot of leeway in these settings so it comes across as a trial & error process for finding what works. Is this normally the case?

 

Pyang, thanks for the settings and I'm going to create a preset with them for "when all else fails" scenerio. I really want to try and get my brain around this whole qmc/noise deal and how it all works but I appreciate your input

[Brian Smith]

Stef, thanks for the clarification on the gamma. I use a few different lights so that i can adjust levles and colors for some dramatics. Being office furniture it needs all the help it can get

 

Brian, I made the changes that you suggested in regards to the QMC GI and there really was no major change. I went ahead and made a few tweaks to the QMC Sampler and although not 100% it does look a bit less noisy. The main area of the noise is under the horizontal surfaces.

 

I've got things set as follows, take a look and let me know where I can make some more tweaks to kill the noise monster

 

QMC Adaptive Sampler: 3/12

QMC GI: Subdiv 40 Secondary Bounces 3

QMC Sampler: Adaptive amount .85 Noise Threshold .003 (won't go any lower) Min Samples 11

 

Any thoughts are greatly appreciated and thanks for reviewing the min/max sampling process. There seems to be alot of leeway in these settings so it comes across as a trial & error process for finding what works. Is this normally the case?

 

Pyang, thanks for the settings and I'm going to create a preset with them for "when all else fails" scenerio. I really want to try and get my brain around this whole qmc/noise deal and how it all works but I appreciate your input

 

as i said, if you still have noise after improving your qmc gi, then the noise has to be caused by image sampling. you say you are using a max rate of 12, but you didnt specify your Clr thresh value (or whether you still have it linked to Noise thresh). in my opinion, you should ALWAYS disable the Use Clr thresh option so that you can change the image sampling quality without adjusting the Noise thresh value (which affects every blurry affect in vray). that max rate of 12 is useless btw, if you dont have a low enough Clr thresh or Noise thresh value. Personally, i would never want vray to make 12 subdivs, but even if i did, i dont think a value of 0.003 will allow the 12 subdivs to be taken. you might have to make it .002 to allow it.

[bmcgonigle]

Brian, I was a bit sidetracked yesterday with a project but i was able to pick up on this noise issue again this morning and think I've made some pretty good progress. I took into account what you said about the QMC clr thresh, deselected the sampler thresh, changed the clr thresh to .003 (i can't get this to go any lower, when i switch it to .002 it jumps back to .003, can you tell me why this is?), set the min/max to 1/16, put hsph to 100 and interp to 50 as pyang had suggested (this cleared some model darkness issues so good call there) and set the QMC subdivids to 40. I ran this and had some better improvements on the noise issue but nothing that wowed so I did a little searhcing on the site and came across a post by Fran that recommened setting the VRay light smapling subdivids to 14 or so. I did this and ran the solution and low & behold my noise is gone ..or small enough that i can't see it.