Below is a list of features supported and unsupported in this phase one release of XPU

Rendering

Notes :  

1. Lama support will be implemented in a future release.
   
   
2. In XPU, we support the following SSS models

• • Burley Normalized
  • Exponential Path Traced
  • Non-Exponential Path Traced
    
    subsurfaceSubset is not yet supported

Patterns & Textures

Notes : 

1. Dynamic String construction in your own patterns is not supported
   
   
2.  There is no support for custom plugins
   
   
3. PxrSeExpr not supported
   
   
4. PxrDirt & PxrCurvature require the trace() OSL call, which is not yet supported.
   Support for a single level of recursion will be added in a future release.
   
   
5. Point clouds not supported
   
   
6. PxrBakeTexture and PxrBakePointCloud not supported
   
   
7. Dynamic path construction in your own patterns is not supported, but please note that we do support the following path tokens <UDIM>, <u>, <v>, <U>, <V> and <primstr:varname> that will result in a "dynamic" path to your textures.  <primstr:varname> can be used to reference the value in a constant primvar or user attribute to build a dynamic path.  Also note that <primstr:varname> is not in beta1 for XPU, but will be in a later beta.
   
   
8. XPU samples textures at one MIP level coarser than RIS so that it may store more textures in limited GPU memory.  This results in slightly blurrier renders from XPU than RIS.

Lighting

Notes : 

1. Light Filters & Light Linking are currently not supported
   
   
2. "shot" based lighting features will be available in future releases.  Examples include:
   
   1. Emission Focus
   2. Light groups
   3. Manifold Next Event Estimation
      
      
3. Thin shadows are currently not implemented.
   
   
4. Mesh lights, PxrCylinderLight and PxrEnvDaylight are yet to be supported.
   
   
5.  XPU does not support colour temperature on lights yet. This means the correct colour space won’t be applied when a temperature is converted to an RGB value

Geometry

• Catmull-Clark Subdivision

Notes : 

1. Loop Subdivision.  Catmull-Clark for both quads and triangles is supported
   
   
2. Points.  Have been partially implemented.  Point falloff is not yet supported
   
   
3. NURBS
   
   
4. Quadric
   
   
5. Blobbies
   
   
6. The built-in curvature doesn't match RIS and will be receiving enhancements in a future release
   
   
7. Nested instancing
   
   
8. Object attributes such as maxdiffusedepth and maxspeculardepth not yet implemented

Integrators

• PxrPathTracer
• PxrDefault
• PxrDirectLighing
• PxrVCM

Notes : 

1. numBxdfSamples, numLightSamples, numIndirectSamples (and their manually set counterparts) are not supported.
   
   
2. PxrOcclusion, PxrVisualizer and PxrUnified are not yet supported.
   
   
3. clampDepth and clampLuminance (used to suppress fireflies) have not been implemented
   
   
4. Russian Roulette has not been implemented
   
   
5. allowCaustics is always 1

Rendering

Notes :

1. XPU currently only outputs EXR or TIFF frames
   
   
2. PxrCamera not supported yet.
   
   
3. Adaptive sampling is yet to be implemented
   
   
4. Motion blur has not been fully implemented
   
   
5. Trace Subsets have not been implemented.  This then impacts the subsurfaceSubset feature of PxrSurface
   
   
6. Volumes not yet implemented
   
   
7. User defined AOVs or LPEs not yet implemented
   
   
8. Only some geometric built-in AOVs are available under the same name they are available for RIS
   
   
9. Holdouts, shadow collectors not yet implemented
   
   
10. Deep Output. Coming soon.
    
    
11. Multi-camera, multi-frame are not yet supported
    
    
12. PxrOcclusion, PxrUnified integrators are not supported.
    
    
13. The built-in curvature calculation different is different to RIS, which results in differences in specular mollification.
    
    
14. The "weighted" option for the pixelfiltermode parameter to the Hider is not yet supported.
    
    
15. Procedurals not supported.  However, if you are using the latest XGen in Maya, you should get renders of your data.
    
    
16. Baking - either at the pattern level via PxrBakeTexture or at the renderer level to bake global illumination is not yet supported.