How does VrayMTL translucency work...?

[svetlozar.draganov]

Hello again,

Here some good news about Maya users - the same scene with the same settings converted to Maya looks this way:

Unfortunately they are not identical because Translucency algorithms between Max and Maya are different.
If the above example I have changed Maya's Translucency settings to the one I set previously in Max but there are some differences for example > Wax Type is missing here.
In Maya actually we have a lot more control over the translucency - because we are able to set Scatter Bounces in Max we only have 1 bounce.
However the same technique could be applied here in order to prepare translucent materials - here are a few example with a few tweaks on Fog-Multiplier / Scatter Bounces / Subdivisions - everything else is the same as in Max scene.


Maya and Max Scenes >>
translucency_Maya.zip
translucency_Max.zip

[Dariusz Makowski (Dadal)]

Woo hooo you are AWESOME !

Thanksss... May the translucency fun begin!

Regarding scatter bounces is that physically accurate? The entire translucency how accurate is it or we have some hax going on in there?

Thanks, bye.

[sersia]

Thank you for the good information.
It is quite nice!! Check the ear.

[svetlozar.draganov]

Thank for for the feedback - it looks really nice

[LudvikKoutny]

Wow, thanks very much. I did not expect such an in-depth reply. You should definitely put this on Spot3D

Anyway... i still think tweaking SSS parameters could be a bit easier and straightforward if scattering depth parameters were in scene units. Controlling numerous parameters in abstract units is possible, now when i understand the approach, but it's still not easy to deal in data i have estimated based real world distance. That for example material X has scattering depth of top layer about 1 cm. Maybe it could be simplified in future

Non the less, the tutorial is great, and now i know what to do and i am finally getting some acceptable results, so thank you

[pg1]

Very good information.

How does this relate to the vray sss shader? vs the 2 side material.

Playing around with the scene you posted I was able to re-create the image using the vrayfastSSS2 shader pretty closely.

The way I think of it at the moment is
an object with no width = 2 side material
Translucency = an older and cheaper render to create sss
SSS = the most accurate but expensive

Does that sound right?

[svetlozar.draganov]

How does this relate to the vray sss shader? vs the 2 side material.

The setup of FastSSS and 2SidedMtl is similar but not the same as VrayMtl with Translucency.

an object with no width = 2 side material
Translucency = an older and cheaper render to create sss
SSS = the most accurate but expensive

2SidedMtl is the best approach for objects with no volume. It is very fast and it generates very good results. This shader could be used also for objects with volume but it will not be as precise as other shaders. 2SidedMtl has improved a lot in the latest V-Ray 3.1:
https://www.youtube.com/watch?v=Hy-t...etailpage#t=76

Translucency - it is an older approach but it generates more accurate result than FastSSS2 and because of that it is slower.

FastSSS - this material is optimized for SSS calculations of objects with volume, it generate much faster but less accurate result than VrayMtl with Translucency.

In V-Ray 3.x there is one more addition on that subject and this is VrayScatterVolume material.
This is a unbiased method which will generate as accurate result as Translucency but it is easier to setup.

Here are some examples:
https://www.youtube.com/watch?v=wOw_vRMCuo0
https://plus.google.com/+VladimirKoy...79421619738074

[pg1]

Thanks for that Svetlozar.

The Translucency is more accurate and slower, that surprises me a little bit. In my brief test using your scene I got very quick results with Translucency, 3 seconds vs 15 seconds with fast SSS to get a similar result.

I will give the VrayScatteVolume material a try

[davision]

Just want to echo what the others said -- this was a great explanation of translucency, Svetlozar. So thank you...

[davision]

I wanted to try passing an object through the translucent volume and then also get some fuzziness to that object (using refraction glossiness). As soon as refraction glossiness is set less than 1, the rendering seems to freak out. Is refr. glossiness not okay to use with translucency?

See attached. I used your sample scene as a base but I increased the refraction color value a bit and then changed ref. gloss to .99. The only difference between the man on the left and the right is translucency is disabled on the right.

[tashko.zashev]

I wanted to try passing an object through the translucent volume and then also get some fuzziness to that object (using refraction glossiness). As soon as refraction glossiness is set less than 1, the rendering seems to freak out. Is refr. glossiness not okay to use with translucency?

See attached. I used your sample scene as a base but I increased the refraction color value a bit and then changed ref. gloss to .99. The only difference between the man on the left and the right is translucency is disabled on the right.

[ATTACH=CONFIG]22144[/ATTACH]

Hi,

Which V-Ray version is this? Can you post the scene file ?
Maybe there is something broken between the versions.

[davision]

It is not the latest version of Vray. I will try the service pack and if the problem is still there, I'll post the file.

[Syclone1]

so I opened the file in 3dsmax 2014 and V-Ray 3.10.02 and getting some weird artifacts, not sure whats happening lol?

[vlado]

so I opened the file in 3dsmax 2014 and V-Ray 3.10.02 and getting some weird artifacts, not sure whats happening lol?

There are overlapping triangles in the scene (there is a plane that is exactly aligned to a VRayLight). Not sure why Svetlozar set the scene up this way; it's best to avoid overlapping faces.

Best regards,
Vlado

[Syclone1]

There are overlapping triangles in the scene (there is a plane that is exactly aligned to a VRayLight). Not sure why Svetlozar set the scene up this way; it's best to avoid overlapping faces.

Best regards,
Vlado

Ah that explains it, didnt see that lol