V-Ray RT -> Invisible Objects

[pixelwerk]

I'm still the oldschool CPU-render-guy, but thought I'd give VRay RT via GPU a try. When I'm trying to render a scene that renders fine with RT/CPU with my GPU (Quadro K4000) in the prepass all elements are there, but once this pre-pass is done, certain elements disappear. Since only the meshes with the same shader applied seemed to be affected by this, i thought, maybe it's shader related. So i manuallyassigned a new, clean shader to these meshes. This worked until a certain point, where several meshes started to vanish again that were visible before.

[vladimir.nedev]

Can you send me the scene ?
Do you see any warnings / errors in the Event Log ?

Greetings,
Vladimir Nedev

[pixelwerk]

I wrote you a PM with the download-link to the scene.
The event log looks pretty clean. No errors and the only warning i get is, that the license ist about to expire soon. That's it.

[vladimir.nedev]

Under the Vorbaurolladen folder, all the meshes seem to have some auto-generated part tags. Probably by some importer plug-in. Can you tell me which plug-in you used to import that geometry ?



Can you delete them and try rendering with RT GPU again ?
These part tags will cause the V-Ray for MODO exporter to create one material slot on the mesh for each of them. This is a lot of material slots, so some internal RT GPU limit is probably reached.

I need to optimize the export for this case, but it will require changes to how materials are updated in RT.
I will need to take care of the case, when a material group is added to the Shader Tree with a tag that wasn't present in the Shader Tree before.
This can change the material slots for any mesh with the tag, so the mesh needs to be re-exported as well.
So, it won't be a trivial change unfortunately.

Also, you have a texture that uses the Stencil effect, that's not supported in RT GPU in V-Ray for MODO yet.

Greetings,
Vladimir Nedev

[pixelwerk]

I was importing the STEP-Files from the customer via the PowerTranslator Plugin. It creates a Material for each assembly in the CAD-files. In most cases i don't care about them too much, since most of them are not visible in the render i delete these materials, and let MODO use the default material for them.

I know that stencil doesn't work...The scene is not optimized for GPU-rendering. I was just playing around and since everyone is so into GPU-rendering i thought i'll give it a try and see the speed difference. The K4000 is for sure not the best solution for GPU-Rendering anyway

After doubleclick on the layer, selecting all it's meshes inside and using Geometry -> Polygon -> Set Part and create a new Part, all these useless parts are gone, and it's rendering fine now

[vladimir.nedev]

I was importing the STEP-Files from the customer via the PowerTranslator Plugin. It creates a Material for each assembly in the CAD-files. In most cases i don't care about them too much, since most of them are not visible in the render i delete these materials, and let MODO use the default material for them.

I didn't see too many material tags in your scene, it is the part tags that are the problem.
You don't need to have a material in the Shader Tree for each part tag to have the problem, internally V-Ray for MODO will create a slot for each part tag, even for those that are not in the Shader Tree.
Maybe the PowerTranslator plug-in has an option to disable the creation of the part tags.

I know that stencil doesn't work...The scene is not optimized for GPU-rendering. I was just playing around and since everyone is so into GPU-rendering i thought i'll give it a try and see the speed difference. The K4000 is for sure not the best solution for GPU-Rendering anyway

Yes, at least on paper the K4000 should be something like 6 times slower than a GTX 1080.
But they are using different architectures, so in practice the difference might be less or more.

I use this wikipedia page to compare GFlops on different cards, within an architecture, I think it might give you a good idea what's the best buy : https://en.wikipedia.org/wiki/List_o...ocessing_units

Greetings,
Vladimir Nedev