Q; Vray proxy and subdivision rendering

[Rork]

Hi all,

We're running into a render issue atm:



We have a Fluid sim coming from Houdini (as a highly triangulated Alembic mesh sequence) into Maya as a Vray Proxyobject.
Some of the finer bump details in the render show up as triangular render errors in the highlights of the Carpaint shader.
Bump textures ar 4K .exr files, so it's not that banding is an issue.

As the fluid sim is very active, this results in small 'streaks' of jitter in the highlights of the Carpaint coat.
The bump texture is piped into the map slot of the Carpaint Coat parameters.

We tried to get rid of it by changing every subdiv setting we could find, in the render settings options, and by adding subdiv properties to the Proxy Mesh itself, and changing those values.
Lowering edge lengths doesn't help for the mesh and render settings, adding a smooth operator doesn't help, playing around with the various normal settings checkboxes on the proxy and prxoy mesh don't really help.
The triangular render issues are not really changing much or going away.

We're a bit out of ideas atm, and hoping someone can help out in the gray noodle department.

So any tips, tricks or thoughts are welcome. We're at the end of the project and it's holding it all back now..

cheers!

rob

p.s. Maya 2019.2 & Vray Next update 1. Alembics from Houdini 17.5

[Rork]

Hi,

It seems the exr's were giving us some weird render errors.
We did a quick blur test, and it seemed to go away for the most part.
Looking into the re-creation of the exr's now, and see what works better.

it's a strange issue, as the exr's are 32bit float, so one would think precision would be enough?

Will report back after some extra tests,

rob

[hermit.crab]

Could you send a stripped version of the scene to support@chaosgroup.com so we can investigate? Mention this thread in the e-mail.

[Rork]

Hi Aleksandar,

We investigated the shader setup/renders a bit more, and found out it was some weird form of rounding error in the Ripple shader setup. This was setup in Blender (yup, another 3d app..), so we were a bit uncertain where to start looking.
After changing some of the wiring setup of shaders, we got rid of the subpixel errors in the newly rendered exr's, and bumps rendered fine in Maya after that with the new bumpfiles.

We double checked in multiple 3d apps as well, so see if all was fixed in the renders.

So, in this case, we believe it was some kind of odd math rounding error in the shader tree setup.


Sorry for the noise, and thanks for a great renderer!


rob