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- XPU currently requires a CUDA-compatible GPU to be installed, even if the intention is to run only in CPU mode.
- Behavior of XPU when it runs out of memory on your GPU: XPU will crash if it runs out of memory on your GPU. If you are running XPU inside of Maya, Houdini, or Blender, this will bring down your application as well. Be sure to save often. We are going to work to mitigate the two biggest causes of this condition.
- If you have more than one GPU, we allow you to specify which GPU to use with XPU, but do not yet support the ability to use more than one GPU at the same time.
- Releasing a license: It is possible to get XPU into a situation where it doesn't release the license back to the RenderMan license server. If this happens and you end up using all of your licenses, just restart your application (Maya, Houdini, Katana, or Blender) and you will be able to continue your work.
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- XPU does not currently support redirection of errors away from the console, which means DCCs will not be able to report XPU errors in their UI.
- Warnings on the console when rendering to XPU from Katana. There are some warnings you will see on the console about a bad DSO being found for the socket display driver. You can ignore these.
- Picking from "it" does not relay the selection back to RenderMan for Maya
- RenderMan for Maya does not yet support supports batch rendering to XPU (PxrPathTracer integrator)
Shading
| BxDFs, Displacements, & Patterns | RIS | XPU | Notes |
|---|---|---|---|
PxrSurface | ✅ | ✅ | Some Subsurface modes are not available. Second refraction roughness is not yet implemented. |
PxrLayerSurface | ✅ | ✅ | |
PxrDisneyBsdf | ✅ | ✅ | |
PxrMarschnerHair | ✅ | ✅ | |
PxrConstant | ✅ | ✅ | |
| PxrDiffuse | ✅ | ✅ | |
| PxrDisplace | ✅ | ✅ | |
MaterialX Lama | ✅ | ❌ | |
PxrVolume, Volumes | ✅ | ❌ | |
OSL Patterns | ✅ | ✅ | PxrDirt & PxrCurvature not supported |
C++ Patterns | ✅ | ❌ | |
| PxrSeExpr | ✅ | ❌ | |
Baking | ✅ | ❌ | |
Point Clouds | ✅ | ❌ |
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- Custom Bxdf or Displacement plugins are unsupported.
- MaterialX Lama support will be implemented in a future release.
- In XPU, we support the following SSS models:
- Burley Normalized
- Exponential Path Traced
- Non-Exponential Path Traced
- subsurfaceSubset is not yet supported.
- Single scattering support in PxrSurface is not complete because volumetric light transport is not fully supported in XPU.
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- Light Filters & Light Linking are currently not supported.
- "shot" based lighting features will be available in future releases. Examples include:
- Emission Focus
- Light groups
- Manifold Next Event Estimation
- Thin shadows are currently not implemented.
- XPU does not support color temperature on lights yet. This means the correct color space won’t be applied when a temperature is converted to an RGB value.
- VIRP (visible in refraction path) is not implemented (among other things, it requires LPE support).
| Info | ||
|---|---|---|
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| As the light selection scheme in this phase one release of XPU is yet to be implemented, we recommend keeping the number of lights in your scene to a minimum. |
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| Geometry | RIS | XPU | Notes |
|---|---|---|---|
Subdivision Surfaces | ✅ | ✅ | Catmull-Clark only. No support for hierarchical subdivision surfaces. |
Polygonal Surfaces | ✅ | ✅ | |
Nurbs | ✅ | ❌ | |
Curves | ✅ | ✅ | |
Points | ✅ | ✅ | Some features Falloff is not availablesupported |
| Quadrics and Blobbies | ✅ | ❌ | |
| Procedurals | ✅ | ❌ | |
| Nested Instancing | ✅ | ✅ | Varying attributes to drive differences in materials per-instance is not yet supported. Only 4 levels of nested instancing are supported. |
| Watertight dicing of subdivision surfaces | ✅ | ✅ | XPU cannot opt out of watertight dicing. |
| Watertight dicing of displaced polygonal surfaces | ❌ | ✅ | XPU cannot opt out of watertight dicing. |
| Nested dielectrics | ✅ | ❌ | XPU does not support intersectpriority or nested IOR tracking; refractions may be wrong when leaving an inner nested dielectric material |
| Dicing cameras | ✅ | ❌ |
- Loop Subdivision is not supported. Catmull-Clark for both quads and triangles is supported.
- Point falloff is not yet supported.
- Object attributes such as maxdiffusedepth and maxspeculardepth have not yet been implemented.
- Deformation motion blur is not yet supported.
Shading of nested instancing has artifacts. In our tests we have seen shading issues with leaves that are rendered as nested instances.
Inverted normals are possible when doing displacement, depending on the input file and DCC. We have seen this with Alembic being imported into Houdini.
- String and matrix geometry primvars are not supported.
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| Integration & Ray Tracing | RIS | XPU | Notes |
|---|---|---|---|
PxrPathTracer | ✅ | ✅ | Some features not available |
PxrUnified | ✅ | ❌ | |
PxrVCM | ✅ | ❌ | |
| PxrOcclusion | ✅ | ❌✅ | |
PxrVisualizer | ✅ | ✅ | Some features not available |
| PxrDefault | ✅ | ✅ |
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| Pipeline | RIS | XPU | Notes |
|---|---|---|---|
AOVs and LPEs | ✅ | ❌ | |
EXR, TIFF | ✅ | ✅ | |
Deep Output | ✅ | ❌ | |
Matte, Holdouts | ✅ | ❌ | |
| PxrCamera | ✅ | ❌ | |
| Crop windows | ✅ | ❌ | XPU support will be available in 24.2. crop windows in 'it' will be available in 24.4. |
| Advanced DOF controls (bokeh, etc) | ✅ | ❌ |
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