FastSSS2 - strange artifacts when single scatter in raytraced solid mode

[Mnietek2707]

As said in title.
When single scatter is set to raytraced - refractive, things look OK.
Reflections are disabled so this is not a reason.
Is this a bug?

[vlado]

Which V-Ray version is this?

Best regards,
Vlado

[vlado]

Nevermind, I think I could reproduce that - is your geometry self-intersecting?

Best regards,
Vlado

[super gnu]

i think i can answer that, its a standard max primitive unless im mistaken, and yes, its a horrible intersecting mess.

[Mnietek2707]

Sorry for late response.
V-Ray version is 3.10.03.
Artifacts appear even on simple, clean mesh.

Here is max file (HDRI removed and used Vray color instead)
SSS problem01.zip

[Nkal]

Sorry for late response.
V-Ray version is 3.10.03.
Artifacts appear even on simple, clean mesh.

Here is max file (HDRI removed and used Vray color instead)
[ATTACH=CONFIG]23119[/ATTACH]

Hello Mnietek,

I had a quick look at your scene, there seems to be a problem with the shader and it is not due to the models, couple of things to mention here:

1- I switched to raytrace and simple combo and it rendered fine with no artifacts, now if you are going for a more dense liquid feel, this may not be the best option to use, and while the other setup is producing some artifacts it is also rendering slower, i can advise at this stage to look into normal vray material and enable "hard wax" option with refraction for any dense liquid renderings, this also in certain situations does render faster and may look better and more believable for liquids than the fast sss and may get the job done for now.

2 - Having mentioned the above, Vray 3 comes with a serious SSS issue which has not been addressed yet, this may or may not be related to your problem but those artifacts seem very similar to some of the things we were experiencing, please refer to this thread:

http://forums.chaosgroup.com/showthr...der-one-thread

This has caused us much headache especially when it came to characters and eyes and just about any object interacting with skin, we had to resort to a lot of hard work cheating things to get things out right and on time but it did set us back on our schedule since it was an unexpected issue and continues to be which does not exist prior version 3 and raytrace SSS, we hope the good folks at Chaosgroup are busy fixing this very critical issue.

Hope this helps.

[vlado]

For this case, this is not a bug. The "raytraced (solid)" mode only traces the single scattering until the first hit inside the object and assumes you have no other geometry inside (I was hoping that the "solid" part would be a clue... perhaps it needs to be made more clear). Since you have a hollow part inside the object, the contribution from the other part of the shell is ignored, which causes the darker appearance of the material there. In this case you will have to use the refractive mode.

You could also try the VRayScatterVolumeMtl material, though you really need a nightly build for that.

Best regards,
Vlado