Please bring back prepass based scattering in the VrayFastSSS2 material for Vray Next!

[ben_hamburg]

hey there,

I finally got around to test Vray NEXT. My biggest concern was the removal of the prepass based scattering in the VrayFastSSS2 material.
I do a ton of medical animation and most of my shots consist of 100% VrayFastSSS2 materials with VrayDisplacement mod, which render much faster with prepass based scattering, than with raytraced scattering, with virtually the same look.

So I did my test and results are very frustrating:

Vray Next, update 1.1, noise level 0.08: 7.24 min
Vray Next, update 1.1, noise level 0.02: 27.45 min
Vray 3.6, noise Level 0.08: 1.55 min

So to get the same noise free image, i have 14 times higher render times.

This makes upgrading not an option for us right now and once 3.6 is going end of line, we will have a massive setback with our rendertimes.

So PLEASE bring back prepass based scattering for vrayNext. You could even make it maxscript only, like the adaptive subdivision was for a while, I don´t care.
Or make prepass rate 1 the default setting, so people (like me) stop complaining about flickering...

I don´t need object based scattering, if you still wanna get rid of SOMETHINg...

[Svetlozar Draganov]

14 times is indeed too much time difference.
Can you send me a scene created with 3.x with render outputs and render times from 3.x and 4.x respectively so I could see if there is a way to reduce render times without changing the quality much?

[ben_hamburg]

Hey, I already sent those infos including the scene file to support, ticket number is 828-338-566, if that helps.

[Svetlozar Draganov]

Thanks, we are looking it right now. At first look I could confirm the rendering is slower with Raytraced mode but this is expected because the method is more precise than Prepass-based illumination map.
Denoiser will certainly help to reducing render times but I'm not sure if reaching the same render times are possible cause the difference in the noise levels is just too much.
I'll discuss that matter with our devs and will let you know if something comes out.

[vlado]

There are still things that we can do to optimize the raytraced calculations; I would prefer to focus on those first.

Best regards,
Vlado

[ben_hamburg]

Well, if it isn´t something that more people want, I understand if its not your priority. i´m usually not fond of keeping "outdated" methods just to please some old hacks either...too bad I´m an old hack myself now...

[ben_hamburg]

And I´m hoping that Vray 3 is still being supported for at least 2-3 more years, when technology has gotten better and the switch won´t be as harsh as it would be for us right now.

[Svetlozar Draganov]

I added a new improvement-request into our bug-tracking system and attached the scene you sent us so as Vlado suggested we'll try to optimize Raytrace mode of FastSSSMtl.
Regarding the support of V-Ray 3.x - there will be no more bug-fixes or features for version 3.x, entire development is now directed to V-Ray Next. Our Support Teams however will continue supporting 3.x till the release of the next major version.

[ben_hamburg]

I added a new improvement-request into our bug-tracking system and attached the scene you sent us so as Vlado suggested we'll try to optimize Raytrace mode of FastSSSMtl.

Sounds good. In our case we usually have very strong SSS effect with little to now shadowing, I think I played around with that a bit in the past and maybe with shadow computation is the most speed to gain.

Our Support Teams however will continue supporting 3.x till the release of the next major version.

Not sure if I get this right... you mean next major version of Vray.3.x? Or next version of 3ds Max? Because if you stop supporting next version of max, we´ll have to start adjusting now...

[^Lele^]

Not sure if I get this right... you mean next major version of Vray.3.x? Or next version of 3ds Max? Because if you stop supporting next version of max, we´ll have to start adjusting now...

v-ray 3.x will be supported until v-ray 5.x will come out. So a while to go still.

[ben_hamburg]

Ok, cool. Thanks for clearing that up! Thats a wile to go and chances are either optimisation has gotten better until then or hardware faster...

[ben_hamburg]

Just to add to this: I would also be fine with a legacy Version, just like there still is VrayFastSSS (which I don´t use)...so have the new, raytraced only version for everyone else, and then the old faky prepass version for people on tight schedules like me...

[andylewisart]

For whatever it's worth, we are holding off on purchasing Next due to Prepass-based illumination maps being taken out of the FastSSS2 shader. We also do medical animations that are often full-CG shots where everything uses SSS. I did render tests between 3.7 and 4.3 last week and found that my scenes rendered much more slowly because all my shaders were being forced to raytrace. Other scenes without the FastSSS2 shader predictably rendered quicker with Next.

As mentioned above, the prepass-based illumination maps may be a hack, but they typically look good enough and render so much more quickly.

[ben_hamburg]

Aha! I´m not the only one...
thanks for the +1 on this...

[ben_hamburg]

Hey guys,

I´m necroing this thread now, since we are now at a point where the SSS issue is keeping us from updating to the next 3ds max version (2021), since 3.7 doesn´t support Max 2021. We also missed our window to upgrade to Vray5, so we´ll need to to a full purchase for our farm.
We don´t wanna lag behind further, because there is no development in this, but maybe there was and we just missed it.
So, whats the current status of the sss rendering?
Is it not possible to add a legacy shader using prepass mode?
Or have the speeds drastically improved?
What about GPU rendering?
Our farm is still CPU based, but if there is a much faster solution using GPU, we might consider adding a few GPU nodes for the medical stuff, or even switching the whole farm to GPU, as we still do a lot of medical animations (hey, covid 19!)..