VRay Composite Halos (NON-alpha area)

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  08 August 2013
VRay Comp Problem: Halos (NON-alpha area)

Long time admirer of the boards and artists here. First post. Thanks very much for your attention & time.

I searched around the web and these forums quite a lot. There is an extensive thread about vray comp'ing that ironed out some of my troubles, but not this one. Getting down to business:

I've got a halo appearing in a non-alpha area of an image when I multiply the Diffuse Filter pass and the RawLight pass.

Platform: 3DSMax 2013
Renderer: Vray
Composite Tool: After Effects CS6

Max Output Gamma: 1.0

Vray Color Mapping:

Render Elements Params:

The AE project is set to 32 bit and I've confirmed that my EXRs actually contain 32 bit data.

Here is the offending composite with halo:

And this is the rgb color / final render output from max:

The textures & geometry in the above area don't have gaps and they don't have any alpha / opacity at all. The rest of the comp is pretty well spot on.

Last edited by LeadCarbonate : 08 August 2013 at 10:49 PM.
  08 August 2013
In Ae's project settings, have you ticked "Blend layers using 1.0 gamma"?
  08 August 2013
Yes. The option at my end is "Blend Colors Using 1.0 Gamma" but I'm assuming that's what you're referring to. Depth is set to 32 bit float as well.
  08 August 2013
I tried just about every permutation of interpretation I could work out for AE.
  08 August 2013
For the sake of troubleshooting I removed the materials on there and just inserted default vray materials with similar colors. Same result.
  08 August 2013
Then I don't understand why this artifact appears I also work with 32bit exr's and do not have non-alpha halos. Look, in the attached image I've replicated what you did. By the way, I use the same vray and max settings as you do. So our results should be identical. I can send you the project file if you want.

  08 August 2013
I did some test of my own and I only see this issue when there's high contrast in the diffuse pass. I tried the scene with a material override and the issue can't be seen because the only edge cue that exists is in the rawLight pass. I think the key here is that there are two competing edge cues that don't register.

I will simplify my scene and upload a test that other people can try ASAP.
  08 August 2013
Alright -- here's a scene that is representative of my scene. I can reproduce the same issue in this one and although there are a few texture files referenced, you don't need them to reproduce the issue.

Example Scene 01

I render to the vray buffer and I then import the raw light and diffuse filter. Multiply raw light with diffuse filter and the halo appears. Compare this with the straight light pass comp'd by Vray.

Thanks again for helping me to track this down -- I go at these things on my own for as long as I possibly can but this one has me treed.

Last edited by LeadCarbonate : 08 August 2013 at 06:22 PM.
  08 August 2013
The madness continues. Thanks to everybody that's looked at the problem so far. It's like all of the light areas of the image are getting biased a little wider by the anti-aliasing filter. I tried turning it off under "Antialiasing Filter" but as Inigo Montoya says "I do not think it means what I think it means."
  08 August 2013
I've checked your scene and in fact did got that halo thing. However I tried to replicate it with some vivid color boxes and got no artifacts. In other test I even changed vray plane light's color to blue as in your scene and everything turned out fine after compositing. I admit, there's something wrong in your case, but I think you should try starting from scratch and see if it solves the problem.

Last edited by X-RUST : 08 August 2013 at 11:16 AM.
  08 August 2013
It would be best to not use the "raw" channels directly out of V-Ray; instead compute them from the other two channels (i.e. raw lighting=lighting/diffuse filter; raw GI=GI/diffuse filter etc).

Best regards,
  08 August 2013
@Vlado -- That's a fascinating approach that does give me some additional control over the final image. However, the artifact I'm trying to correct is still lurking in the chain. I did a quick color correction test on the diffuse layer which I then recomped with the computed raw light (light / diffuse, per your suggestion) and the halo is back -- just in a new form. Still, I will remember this tip for many other uses.

@X-RUST -- thanks for taking the time to setup another test scene. I've been trying to reproduce the issue similarly. I think a key factor is that there is a visible edge in both the rawLight pass and the diffuse pass. Both passes have to have a clear edge there otherwise there's nothing to be out of registration.

I did two tests: in one I created a completely new scene and roughly recreated the circumstances but with a simple box and two contrasting materials. The difference in my scene is that I put one material on the top faces where the light was facing and the other on the bottom where it was just getting a bit of reflected light.

The result was not anywhere near as dramatic *but* it did produce a subtle halo.

I eliminated GI so I know that's not a factor. I've also done this with raw colors and I still get the issue so it doesn't appear to be a bitmap or a material settings issue (unless it's an issue with the default vray material settings.
  08 August 2013
Just made a test with a Multi/Sub object on a single box

It's just way too incomprehensible why it goes like that. It seems like only Chaos Group knows why is this happening.
  08 August 2013
Thank you very much for confirming this issue at your end -- even though it's not yet solved at least the sanity of my machine and I are no longer in question!

I'll continue to post any updates as I pick this problem apart. I wonder if it would appear if I could completely remove all anti-aliasing. Off the cuff I'm not sure how to do this but I should probably give it a go.
  08 August 2013
Hope you'll find the solution, I'll keep an eye on your updates
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