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Important Differences
- The default coordinate system known as "current" is no longer camera space. Instead "current has changed. "Current" space is context dependent and subject to change
- Displacement is Object Space
- Bxdf is in World Space
- Analytic Lights are in Object Space
- Light Filters are in World Space
- Integrators are in World Space
- Sample Filters are in World Space
- All geometry is an instance
- Note that the light angle parameter on lights has been corrected to use the correct measurement in degrees from the edges. This will alter the look of older scenes.
- We do not include the Librix library
- This Alpha release does not include example files
- RtToken has been replaced, any string that is passed to the renderer must be a RtUString
Deprecated Ri Calls
- RiEdits do not function
Deprecated Options
- Ri:Clipping
- Ri:DepthOfField
- Ri:PixelFilterName
- Ri:PixelFilterWidth
- camera:zblur - use camera property
- dice:pretessellate
dice.maxhairlength
- limits:nearhither
- polygon:pretessellate
- polygon:nonplanar
- polygon:reducedmemory
curve.orienttotransform
searchpath.resource
statistics.endofframe
limits.zthreshold
options.shutter
options.polygon.*
options.hair.*
rerender.logrange
rerender.progressive
hider.bake.pixelSamples
Deprecated Camera Options
- nearhither
- focusregion
- zBlurNearDistance
- zBlurNearDiameter
- zBlurNearFocusDistance
- zBlurFarDistance
- zBlurFarDiameter
- zBlurFarFocusDistance
Deprecated Attributes
- Ri:CoordinateSystem
- Ri:ScopedCoordinateSystem
- bound:displacement
- compatibility:oldmotionfactor
- curve:widthminsegments
- derivatives:centered
- derivatives:extrapolate
- dice:instancestrategy
- dice:instanceworlddistancelength
- dice:maxangle
- dice:preservecv
- dice:relativemicropolygonlength
- dice:resetrelativemicropolygonlength
- dice:stitch
- dice:tessellateretainbspline
- dice:hair
- dice:roundcurve
- displacementbound:transform
- hider:mattemode
- polygon:reducedmemory
- procedural:attributes
- shade:frequency
- shadegroups:attributecombining
- stitchbound:transform
- trace:gritcurves
trace.decimationrate
trace.displacements
- volume:compressionerror
- volume:deptherror
Miscellaneous Changes
- Everything is now an instance within the core of the renderer
- The default (current) coordinate space is different. We now render in world space. Previously this was all in camera space. This affects features like the P AOV.
- Many shading operations are now in object space (displacement is particularly affected and will likely require lookdev or shader changes).
- Any string that is passed to the renderer must be a "UString" or "unique string"
- Curves with normals are supported, as are round curves. But curves with no normals as a notation for desiring always camera-facing curves is not supported. as such, orientation and reverse orientation for curves is no longer supported.
- For subdiv faces, face edits higher than depth 1 are not supported
- Motion vectors have changed
- RxGetContext is removed
- RixTransform API is not the preferred way
- Added circular bucket/tile order
- Default cache limites have been increased to better reflect modern machines
- Pointmemory and Octreememory are both now 20480
- Ptexturememory limit is now 32768
- Opacitycachememory is 1048576
- Brickmemory is 2097152
Known Limitations
Interactive/Live Rendering Limitations
- RiEdits do not function, these are deprecated
- Camera edits do not update, only camera tansformations (Depth of field, focal length, etc requires restart)
- Changes to Presence do not update
- Motion Blur will disappear during interactive rendering with scene changes
- Displacement does not update on changes
- Objects are not re-diced during interactive sessions
- Mesh lights cannot be interchanged as geometry without restart.
RenderMan Pro Server
- We do not read point data from OpenVDB files
- Analytical lights placed inside volumes may yield artifacts when made visible to the camera. As a work around, the light camera visibility should be turned off, and a geometry with a similar shape should be used (visible to camera, invisible to transmission and indirect rays), with the proper emissive bxdf.
- Using the '.' character in the handle for an OSL shader could cause unpredictable results during re-rendering.
- Per-Instance baking is not supported, only the reference instance.
- 3d baking: no direct bake-to-ptex support.
- PxrBakePointCloud cannot directly render ptex.
- No RixPTC/pointcloud API (so PxrBakePointCloud cannot read ptc files).
- Sample/Display filter plug-ins do not have access to lighting services for light dependent effects, e.g. lens flare.
- Adding new mesh light on existing geometry during IPR results in double geometry.
- For PxrUPBP, If the light source is inside a volume, that volume needs to be defined as Volume “box”
- For PxrUPBP, To get a volume caustic, the object casting the caustic needs to have higher intersectpriority than the volume.
- For PxrUPBP, Overlapping heterogeneous volumes are not working yet. (However, overlapping homogeneous volumes do work.) This will be resolved in the future.
- When attempting to access an array primvar, you must first check the size of the array primvar and allocate the appropriate space. Not doing so may lead to a crash.
- Points and curves cannot have mesh lights attached to them.
- Deformation motion blurred volumes don't currently work with densityFloatPrimVar or densityColorPrimVar. You will need to use a PxrPrimVar node connected to densityFloat and densityColor instead.
Alpha Limitations
Geometry:
- Full support of implicits
- Blobbies
- Dicing cameras
- Face edits to RIB
- Utilize smoothed normals
- Displacement improvements
- Watertight dicing speed
- Cracks
- Brickmaps
Materials:
- OSL completeness
Volumes:
- Pixar Studio feature – Aggregate Volumes
- Soem bugs with results
Lighting related:
- Light Filter Linking
- Lights in instances
- PxrVCM (may have bugs and performance issues)
- PxrUPBP remains experimental
- Holdouts
- Shadow collectors equiv to 21.x
General features:
- Crop Window support
- Load on Demand
- Procedurals not fully supported
- Some baking features
Performance:
- Some performance issues remain
Image creation:
- Display and Sample Filters
- Denoiser bugs remain
- dPdtime and motion vectors not correct
Pipeline features:
- Checkpoint and recovery
- Cryptomatte support (in progress)
- USD direct read in RenderMan
- Alembic material assignment
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