VRay RT problem: is RT CPU different than RT GPU(CUDA)?

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Old 04 April 2014   #1
VRay RT problem: is RT CPU different than RT GPU(CUDA)?

Hello guys, VRay RT has been there for a long time, people created amazing stuff with RT. But it does have all kinds of limitations, so when VRay 3 came out, I decided to give it another shot.

Being aware of the fact that some material types are not supported by RT, I did the following tests, and realized that, not only RT has lots of differences with VRay, furthermore, RT with CPU is TOTALLY a different thing than RT with GPU! How is that possible, giving that the official documents never mentioned differences between them at all.

So, here are my two tests, both are using 1 Vray light, and fastSSS material. They are all using EXACTLY the same everything, except for ONE render setting: RT CPU or RT GPU(CUDA)



The first one's quality was set to lower, so it looks a little flat. That's not the point here. You see, the first two has a very bright reflection, but the last one doesn't have any specular or reflection.

Test 2:



Teapot material setting:


Render setting:


Can someone tell me how exactly I should use this powerful tool to get a consistent result? I don't think this module of VRay is really that bad, after all this same tool helped people created something like this 3 years ago, with SSS material. If you can't get SSS right, this picture is like impossible, right?



Please advice. Thanks a ton!
 
Old 04 April 2014   #2
My guess is it doesn't support that specific shader, I haven't tested it but SSS was a new feature for VrayRT so it's probably a specific SSS shader that's supported, maybe the new skin shader.
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Old 04 April 2014   #3
See this page for more information on supported features in V-Ray RT CPU and GPU. We are working on removing the 'no's from that list.

http://docs.chaosgroup.com/display/...ported+Features

Best regards,
Vlado

Last edited by thev : 04 April 2014 at 08:58 AM.
 
Old 04 April 2014   #4
Originally Posted by darthviper107: My guess is it doesn't support that specific shader, I haven't tested it but SSS was a new feature for VrayRT so it's probably a specific SSS shader that's supported, maybe the new skin shader.


EDIT: Vlad himself just beat me to it

Darthviper's guess is correct. RT GPU dosn't support sss mats. Including the new skinmaterial.

Here's the more limited(than CPU) list of supported GPU features:

Supported features on the GPU
On the GPU, V-Ray uses a simplified version of the V-Ray renderer, which supports only a sub-set of all features of the CPU code. The features listed below are supported; anything else will likely not work.

Geometry

Triangle meshes and VRayProxy objects are supported. Instancing is also supported - see the Instancing and Forest Pro support page.

Lights

Note that even for supported lights, only a sub-set of the light parameters are implemented.



  • Standard lights: omni, spot, directional;
  • Photometric lights with web profiles;
  • VRayLight: rectangle lights with textures, sphere and mesh lights without textures; dome light with textures (for image based lighting or IBL);
  • VRaySun;
  • VRayIES lights with web profiles.
Materials

  • VRayMtl material: diffuse color, (glossy) reflections, refractions, opacity, bump mapping, Fresnel reflections;
  • Multi/sub-object material;
  • VRayLightMtl material (without the direct illumination options);
  • VRayBlendMtl material (without the additive mode option);
Textures

Bitmap textures, the Falloff map, the VRayHDRI the VRaySky maps are supported. Other procedural textures (Checker, Noise etc.) are supported by baking them, provided that they have Explicit UVW mapping type. If the Resize textures for GPU option is turned on, then all textures uploaded to the GPU are resampled to a resolution specified by the GPU texture size parameter in the V-Ray RT settings in the Render Setup dialog. The Mix and ColorCorrection textures are also supported.

Cameras

  • Standard perspective views; depth of field is not supported for these views;
  • VRayPhysicalCamera with support for depth of field and bokeh effects;
  • Stereoscopic rendering is fully supported on the GPU.
Environment mapping

Only the background texture from the Environment dialog is supported and used for background, GI, reflections and refractions. Only spherical, mirror ball and angular environment mapping types are supported.

Motion blur

Motion blur is supported, provided that the Motion blur option in V-Ray RT is enabled and motion blur is enabled in the production renderer or through a physical camera.

 
Old 04 April 2014   #5
OH MY GOD!!! Am I in my dream? The ALMIGHTY Vlado is here!!!

(I guess you got that a lot )

Yeah, I was aware of the differences on the supported features between V-Ray and V-Ray RT, but didn't expect the differences between RT CPU & RT GPU.

I guess you and your genius colleagues must have thought of this: is it possible to blend all the features together, but give GI to RT GPU, hair and fur to CPU?

Please forgive me. I just love V-Ray hopelessly and desperately want it to be better than perfect, since its early beta, and ALWAYS voted for V-Ray against fR and Brazil.

Thank you musashidan and darthviper as well :-)

Originally Posted by thev: See this page for more information on supported features in V-Ray RT CPU and GPU. We are working on removing the 'no's from that list.

http://docs.chaosgroup.com/display/...ported+Features

Best regards,
Vlado
 
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