Vray Interior Reflection Speckles (Max)

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  08 August 2013
Vray Interior Reflection Speckles (Max)

Hi there,

I've been modeling and lighting and interior scene on and off in the past month and I'm hoping to finish it soon. It is a large interior scene predominantly lit by VrayLights with a few Omnis to create a bit of illumination on the far walls.

I'm having some speckles appearing in my Reflections. There are no speckles in my GI pass.

Below are links to some renders and screenshots of the problem. This is the latest test render used a Fixed sampler of 3 Subdivs which has the best results so far. Previously I've been using Adaptive DMC, which has been faster but the speckles have been more obvious.

Beauty Pass

Reflection Passes

Screengrab of lights in the viewport

Things that I've done that has helped the problem somewhat
- Increased the Reflection glossiness to 32 subdivs in the table and chair materials. (Everything else is either 8 or 16)
- Removed all VrayLightMtl's from my scene.
- Clamped most bitmaps in my materials if they have their color mapping changed in the output rollout. (Actually not sure if this makes a difference. Does anybody know if it does?)

Things that I've done that hasn't helped much if at all

- When using Adaptive DMC, changing my Min/Max from 1/4 to 2/8,
- Played with the Noise threshold - brought it down to 0.005, but the speckles became even more apparent than 0.01. (Adaptive amout 0.85)
- I've pulled the Adaptive amount to 0.6 which helped the tiniest little bit, but render was an additional 30 min. (Noise thres. changed back to 0.01)

Things that I haven't tried yet
- Sub-pixel mapping (But I previously didn't have much luck with it in past projects.)
- Clamping Vray output to 1.0. And I don't want to do this as I want the color information in compositing.
- Pushing the DMC Max subdivs higher. Render times were already over 3 hours in DMC.
There are a lot of Vray lights in my scene. I think around 300 in total. Most have a multiplier of 20-30 with color, some are invisible and the rest of the setting should be default for all lights.

The current render time on the Fixed Sampler is over 4 hours. If I can get it to work in Adaptive DMC I'll be able to optimize it better.

If anybody is interested in seeing the wip:

If anybody has any tips on how I could re-do my lighting/materials better as opposed to using the current setup, that would be appreciated too.



Last edited by cg-steve : 08 August 2013 at 06:55 AM.
  08 August 2013
Have you tried rendering without your bitmaps enabled to rule out them causing the problems? It doesn't look like a sampling issue to me.
  08 August 2013
Hi David,

No I haven't tried rendering without bitmaps yet. I haven't thought of the bitmaps has being a potential cause of the problem. I'll give that idea a try.

However, say that the bitmaps are causing the problem, what would be the reason, and how would I fix it?

The bitmaps are I think all JPG files. Most are at least 2k pixels large.

  08 August 2013
Could be bitmap filtering on the bump map, I.e. blur value not set appropriately. Or it could be white specs on your reflection/gloss map creating those highlights. Or again it could be a filtering problem on those too.

You could apply an override material to see if the problem occurs still, that could be a fast way to diagnose if it's a material problem.
  08 August 2013
Ok I'll give that a shot too. I did previously lower the blur filter to 0.5 on some bitmaps to make them a little sharper. Perhaps that had something to do with it.

I'll keep you posted on results. Thanks again.
  08 August 2013

Looks to me like the problem could be a JPG compression. Maybe try and put a slight blur on the textures in photoshop and resave as a file format with better compression. I use TGA or even try a tiff.

I say this because the artifacts look similar to the pixelation that you get when you scale up a image to far and those blocks start to appear.

Also try to give a higher bit depth. maybe vray is limiting out on those hot spots from a lack of information.

Are you working in a linear workflow?
  09 September 2013
Hi Guys,

Thanks for all of your insight so far. It's all very much appreciated.

I have an update on my troubleshooting so far.

I've done a test with a material override.
All materials have a singular VrayMtl with no bitmaps.
The diffuse slot has a flat grey color of RGB 128, 128, 128
The reflection is a flat grey of RGB 193, 193, 193
The reflection glossiness is on 12 subdivs
Fresnel is turned on with an IOR of 1.6
- No bump

The results can be see at:

So we can see that the speckles have almost disappeared from the long table (at least on this frame) however still appearing on the table to the right and it’s copy on the far left, as well as on a few chairs.

Splinta, yes I believe I am working in linear workflow.
In a nutshell, my settings are as follows.
Gamma/LUT Correction is enabled with gamma set to 2.2
For bitmap files I have an input of 2.2 and output of 1.0 (I’ve been told recently that I should have input also set a 1.0 and manually change the gamma of indvidual bitmaps to 2.2 if they go in the color slot. Although it makes no difference in the latest test render, is that how I should work in the future?)
In the Vray panel, I have linear multiply on with a gamma of 2.2. “Affect background” and “Don’t affect colors (adaptation only)” is checked, while all other checkboxes in the the Vray: Color mapping panel is unchecked.

And sorry, what do you mean give it a higher bit depth? I believe Vray does its calculations in 32 bit, or are you referring to something else?

Looking at my last render, I’m wondering it those lights above the bookshelves are too bright and potentially creating those hotspots.

Hope this latest render helps narrow down the issue. I’m going to try another render with a lower intensity on those lights.

Thanks again,

  09 September 2013
Have you tried using the DMC sampler at a fully adaptive value?(min/max-1/50, brute force primary) That way you shouldn't have to mess around with individual sampling on materials/lights(recent MR style)
I would definitely stick with the DMC sampler as opposed to fixed, as a general rule.
Are you using any form of IBL?
It's best to leave your colour bitmaps at 2.2 upon import.(Max 2014 defaults to this)
Have you compared your direct/indirect lighting passes separately?

Try using these settings and see if it helps:

DMC min-1 max-25-50 Adaptive=1.0 noise threshold=0.005
AA soften=2.0

Brute force as primary- default settings
light cache as secondary- subdivs=longest pixel dimension of your render
use lightcahe for glossy rays=ON, retrace threshold=ON

Another option is to switch to VRay RT,leave it running through the night, and go to bed dreaming of a noise-free render.....
  09 September 2013

Looking better but there is still some grain in the shadows of the lights close to camera near the lamps and hotspots at the joints of the lamps themselves.

Try increasing the samples on your lights which will smooth that out and possibly clean up the spots. musashidan's workflow of 100% adaptive will do this automatically so its up to you which way you want to work. I usually like to work with the individual sampling. Im old schol like that.

When using the dome light, you need higher subdivs then other vray lights. Also are you using a hdri? If so check the texture resolution. maybe raise it.

With the hotspots at the joint, the "light cache for glossy rays" and "retrace threshold" should help to solve this.

A tip is to change each light to a different colour, like green and red etc. that way you can pinpoint which light is giving you the trouble.

With regards to a higher bit depth. I was refering to your input textures (like colour or reflection inputs) JPG only works in 8bit which may limit the amount of information that vray has to work with.

Your linear workflow is correct but in maya I just check on linear workflow in the render settings, then I dont have to specify gamma, sRGB or linear per texture. Again both work, its up to you which method you prefer.

Have you tried to raise your min subdivs in your global settings. This will force vray to look closer at the darker areas rather then assuming they are correct. Sometimes helps.

Again I am using Vray for Maya but im sure most of this will be across both platforms.

Hope this helps.
  09 September 2013
Hi Guys,
I've finished some test renders with your suggestions. I won't post them but I'll describe my results.

Splinta, your colored light technique worked great. I isolated the problem to those long desk lights and I've set off 2 more test renders with 16 & 24 subdivs and see if that resolves the problem with my current render settings. Also, I've raised global min subdivs in previous tests, but that didn't help much.

Musashidan, thanks for your tip. I've tried your settings and the results were great. The highlight speckles were gone! And the noise is much lower as expected. The only thing was that the render took 8 hours to finish, which is too long as I'd like to render an animation. I've set off a bunch of renders with various settings to isolate the main setting that fixes the speckles and I'll start working on fixing the noise from there. I've never used the 100% adaptive workflow. I suppose I'm also a bit old school with my approach. I'll read up on it and run a few tests vs how I normally work.

I'm not using any IBL. My main exterior lighting is just an FDirect with a VraySky environment and a few different light types for interior.

And yeah I usually work with the DMC sampler. I only tried the fixed sampler as a test to see if that would fix the bright speckling issue.

Anyway, thanks to you guys I think I've almost resolved the issue. I'll post some renders when I get some results.

  09 September 2013
Hi Guys,

It's been a while since I posted but I thought I'd kind of wrap this thread up with my last results, in case somebody was curious on how it went. I hadn't touched it for a few weeks now, but In the end, out of the things that I tested, Mushasidan's worked the best to get a clean result. Bear in mind I'm talking mainly about the bright speckles, but the noise was also much cleaner too.

I thought I tried raising the global subdivs last time, but I was thinking of the wrong setting. I raised the multiplier value this time with my previous dmc settings. It improved the speckle problem slightly, but to get clean noise close the render times were even longer. I suspect that subdivisions is raised in everything, even if everything doesn't need it.

And I sort of expected it, but raising subdivs on those problem lights didn't do much. I may change those lights from Vraylights to one of the max lights with Vray shadows. From past tests, max's lights worked a little better in regard to hotspots and noise.

Anyway, when I have time again to work on the project I'll move it over to the wip thread and post updates there.

Thanks again to all who helped,

  09 September 2013
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