Problem with Motion Blur at production

[haniel1107]

Unfortunately, I have a new problem with motion blur at production.
I have a scene where the camera is moving with a car as a child, only 50km/h fast.

With motion blur the wheels are badly deforming. Rest of the rendering is really good quality.
With increasing the geometry sampling in the render settings, the problem is getting solved, but I need to increase from the default value of “2” to "8" for an acceptable rendering (still not perfect)”.
But this means also increasing the render time from 6 min. to 52 min. per frame…

Already a geometry sample of 6 is killing my 128GB Ram and increases the render time incredibly with a not so great result
This is really an issue… in the past the "Motion Blur Tag" did a good job in such cases… just needed to put a tag on the wheels and the problem was solved…

Is there another trick to get moderate renderings with an acceptable render time with vray5, or am I overseeing something?
Help is very much appreciated.

[deyan.hadzhiev]

Hi haniel1107, the per-object(s) override for geometry samples is not yet implemented in V-Ray 5. Once we add it, increasing the samples just for the wheels will be as simple as it was in V-Ray 3. I have raised the priority for implementing it and will notify you when there are updates on this.

[haniel1107]

Hi haniel1107, the per-object(s) override for geometry samples is not yet implemented in V-Ray 5. Once we add it, increasing the samples just for the wheels will be as simple as it was in V-Ray 3. I have raised the priority for implementing it and will notify you when there are updates on this.

Hi Deyan, thank you! Very happy that you will have a solution for this (hopefully it doesn't take too long). As this will make big differences when rendering animations (Time/Cost)... Thanks!!

[YunalZobu]

I made a quick scene to test the MB.
Using it per camera (from the phys cam tag, not from the RS), can't compare times since the assets are fairly quick to render, but it cleared up a FHD image pretty quickly (attaching a few images)

[haniel1107]

I made a quick scene to test the MB.
Using it per camera (from the phys cam tag, not from the RS), can't compare times since the assets are fairly quick to render, but it cleared up a FHD image pretty quickly (attaching a few images)

What can I say, the models have an extremely large number of polygons, they are from the manufacturer and the environment has a lot of displacement so the scene may not really be comparable, not sure...
But that's why I am asking here.. Without MB the scene is rendering pretty well, except compilling the geometry... this takes a lot of time...

The Hardware is also not the badest... Threadripper 3990X and 2x 2080 Ti 128 GB Ram...
Also what I recognized is with a higher GS the ram gets quickly 100% and as soon this happens, everything is slowing down a lot..
This won't be happen with a MB tag, ...I guess...

[YunalZobu]

I was only trying to get the point across as easily and quickly as possible, that's why I tend always to use a simpler scene setup.
Anyway, here's an example which should be closer to your scene. Adding refractive, glossy and carpaint mats definitely makes the render slower, this one took between 6 and 7 mins. (cpu bucket mode).
Hope this is more helpful.

[haniel1107]

I can only explain what I am experiencing... So if you know how to fix it, it is pretty welcome..

[haniel1107]

Hi Yunal,
I gave it a new trial, as I rather did something wrong, than to wait for software solutions. Just for clearness on my first post with the comparisons... I activated the Mb in the cam tag only. Like you did.
But the GS changes are in the render settings only possible. Here is a new test with gs 4 and 13 min. render time. This time I connected the parts of the wheel at the front wheel. Rear Wheel are still separate objects.. (Never did it in the past, just used a MB Tag on the Null)
I must say the result here is not so bad... this could make a change ... still high render time, but much better... I will do more tests, to find a quick solution..

But a solution like the MB Tag in the past, or what Deyan mentioned, will help to keep the ram low, which I believe is not unimportant and maybe a better MB quality with lower settings
Thanks for inciting me

[YunalZobu]

I'm glad you found a solution.
I'd suggest trying out the MB on a new scene as well, since the setup I've is also using Nulls (wheels are made out of 5 separate objects).

[haniel1107]

I think I was happy too early!
Unfortunately, it doesn't work without increasing the GS significantly.
Otherwise the wheels will start to buckle .. Tried now everything what came into my mind.
Looks only good when you render a still. Hope it won't take so long until the mentioned solution is implemented ...