KtoA introduces Arnold core 

System Requirements 

  • Windows 10 or later, with the Visual Studio 2019 redistributable.
  • Linux with at least glibc 2.17 and libstdc++ 4.8.5 (gcc 4.8.5). This is equivalent to RHEL/CentOS 7.
  • CPUs need to support the SSE4.1 instruction set.
  • GPU rendering works on Windows and Linux only and requires an NVIDIA GPU of the Ampere, Turing, Volta, Pascal, or Maxwell architecture. We recommend using the 460.39 or higher drivers on Linux and 461.40 (Quadro), 461.40 (GeForce), or higher on Windows. See Getting Started with Arnold GPU for more information.
  • Optix™ denoiser requires an NVidia GPU with CUDA™ Compute Capability 5.0 and above.

Katana 5.0v3 compatibility

Katana 5.0v3 introduced a change where the Arnold USD plugins support in Katana may cause an error.  When this happens, Windows a dialog will pop up at Katana startup and during rendering where it will state it cannot find a DLL entry point, while on Linux this will result in aborted startup of Katana with missing symbol. This is a known issue, and will be fixed in a subsequent version of KtoA; in the meantime, the workaround is to downgrade to Katana 5.0v2 temporarily.



  • IPR / live rendering enhancements :
    • Operators on both procedurals and assigned globally now update when changed in live rendering (KTOA-424)
    • AOV shaders and color managers now update when changed in live rendering (KTOA-631)

USD Enhancements

  • Mesh Lights: Geometry lights are now supported in the render delegate (usd#1080)
  • Color Management: When a usd file is loaded, the color manager node is set based on render settings parameters (usd#946  usd#1042) 
  • Motion Blur from Render Settings: A usd scene with Render Settings primitive can be rendered with motion blur (usd#1089) 
  • Varying topologies and motion blur: Support velocity motion blur on geometries with varying topologies (mesh, curves, points) on both the procedural and the render delegate (usd#1090)
  • Support arnold primvars in instances: When an instancer has a primvar for an arnold builtin attribute (e.g. matte), we now propagate it to its instances (usd#1100)
  • Support UsdPreviewSurface displacement output: scenes where UsdPreviewSurface is used as a displacement shader, through its attribute displacement are now supported. This is needed to render the Alab scenes (usd#1130)
  • Support light linking on instances: We can now support setting a point instancer, or an instanceable prim, in light linking (usd#1128)
  • Optimize nested instances in the render delegate: The memory consumption for nested instances (point instancer having another point instancer as a prototype) has reduced dramatically in Hydra (usd#1124)
  • Render NurbsCurves as UsdGeomCurves: Usd Nurbs Curves were previously ignored by Arnold. They are now rendered as basic UsdGeomCurves (usd#1120)
  • Support instanceable prims with variant overrides: It is now possible to render an instanceable prim referencing another primitive, and override its variants (usd#1127)
  • Support per-instance velocity blur: The Arnold render delegate now supports point instancers with varying amount of instances, where it's the velocity blur that drives motion blur  (usd#1092)
  • Usd Writer reuses eventual existing material primitives: This is needed for MayaUsd exports, so that the original mayaUsd material is kept, and Arnold shaders are assigned in the "arnold" context (usd#1139)
  • Support shader connections to lights in Hydra: Using an ArnoldNodeGraph primitive, the Arnold render delegate now supports connecting arbitrary shading trees to light's colors (usd#1141)
  • Support lights filters in Hydra: Similarly to shader connections, arnold light filters (gobo, etc...) can now be assigned to lights, through an ArnoldNodeGraph primitive (usd#1141)
  • Improve shader dependency graph in the render delegate: The tracking of shader connections (for materials, lights, light filters, etc...) is now more robust, and fixes crashes when disconnecting or reconnecting shaders  (usd#1158)

API Additions

  • Universe comparison: The new AiUniverseCompare() API allows the comparison of 2 universes, returning a boolean result. It can receive an optional type mask so that only nodes of types matching that mask are taken into account for the comparison. Finally, it can optionally return a list of all the differences found. (ARNOLD-10171).

Incompatible Changes

  • Connection priority in MaterialX document:  Setting both a value and a connection as input of a node is undefined behavior in MaterialX. Arnold will now prioritize the connection over the value when both are defined. (ARNOLD-11198).


  • Time samples should always clamp to shutter range (KTOA-332)
  • Max time samples does not affect Alembic geometry (KTOA-333)
  • Too many motion keys included with center-on-frame motion blur (KTOA-783)
  • Fix update shelf script python exceptions (KTOA-787)
  • Live material updates not always working (KTOA-788)

  • ARNOLD-12299 - Crash when writing .ass file expanding procs without a render session
  • ARNOLD-12232 - Memory leak when rendering deep EXR layers
  • ARNOLD-11809 - Random crash when rendering multiple scenes in parallel
  • ARNOLD-12211 - [GPU] Optix denoiser memory leak when creating and destroying render sessions successively
  • ARNOLD-12177 - [GPU] Crash with ramp shader after aborting due to an error
  • ARNOLD-12166 - [GPU] Texture memory leak when creating and destroying render sessions successively
  • ARNOLD-12165 - [GPU] Incorrect volume bounds
  • ARNOLD-357     - [Licensing] Licensing error "[clm.v1] product key not found
  • ARNOLD-12144 - [maketx] Unwanted log messages
  • ARNOLD-12171 - [MaterialX] Crash when exporting a volume shader to MaterialX
  • ARNOLD-11198 - [MaterialX] Connection is ignored when a node input also has a defined value
  • usd#1073 Resolve node attributes from referenced files
  • usd#1093 Fix instanceable references in the same USD file
  • usd#1104 Compute visibility until the eventual root prim
  • usd#1129 Support UsdUvTexture relative paths with udims 
  • usd#1133 Set outputs layer names only if required 
  • usd#1136 Fix uninitialized UV coords with leftHanded meshes 

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