Bug with vray 3.40.02 and modo 10.1v2 concerning UDIM

[ratus69]

hi,

I've spent two days of nightmare with vray and modo and I finally realised it was a bug with modo 10.1v2 !!

I've gone back to modo 902 sp3 and it works well

it's about UDIM image not applied correctly in the 1010 tile here :

I was having hard time trying to mix metal with dielectric using refractive IOR maps but I think I understand better how Vray works

in modo 10.1v2 :


in modo 902 sp3:


my file with maps:
bug.zip

[ratus69]

ok i'm having this bug now with 902 sp3 with tiles 1010 and 1020 !!

so it's not related to modo version even if it's the bug is visible in 10.1v2, it finally appears in 902

I will try to update my nvidia drivers

[vladimir.nedev]

It's actually not a bug, it's a limitation of RT GPU when working with UDIM.
The CPU renderer doesn't have this limitation.

RT GPU supports the following range of UVs for UDIM:
U in [0, 9] and V in [0, 8]. This means you can use UDIM tags from 1001 to 1079 , not including the ones that end in 0, like 1010, 1020, 1030 and so on.

We should have this information on the compatibility page, sorry about that.
Also, we should probably increase U to be in [0, 10], so you can use all UDIM tags from 1001 to 1079.
I guess people use U until it reaches the maximum and then go one up in V.

Greetings,
Vladimir Nedev

[ratus69]

thanks for this valuable info and yes it should be extended to all available range of UDIM

RT and VRAY should have the same properties to avoid this kind of lost time and headache...

[vladimir.nedev]

If you are switching between production rendering (Render with V-Ray... command) and RT CPU, they should work the same in terms of shading/materials/textures/etc, since they use the same CPU code.

But, RT GPU is a completely separate engine with separate code.
Also GPU programming is generally less flexible compared to CPU programming, so it will always have some limitations compared to the CPU engine,
although the GPU developers are aiming to reduce them as much as possible.

Sorry for the lost time. If you want to avoid headaches in the future, it might be best to use either only RT GPU or only Production/RT CPU.

Greetings,
Vladimir Nedev

[ratus69]

Hello Vladimir,

I was again fighting with udim in 1010 not functioning for a while when I remembered this limitation...one year later
Do you plan to make the 1010, 1020 .. udims available in RT GPU or do we have to forget about it ?

Thanks

[dangerweenie]

hi there,

i am having this same issue with v-ray 3.6.03 and maya 2018.

are there any plans to update this in vray 3 or vray next?

thank you!

EDIT: I've confirmed this issue is resolved in V-Ray NEXT ... however, substance generated UDIMS, while automatically skip 1010,1020,1030, etc when using V-Ray export preset, still go past 1079, and as such don't seem to work in V-Ray for Maya 3.6