KtoA is a bugfix release using Arnold

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.



  • Faster instancing: instancing via instance array or pointcloud locations is now usually much faster. There are two speedups which will kick in, but have certain caveats where they cannot be applied. We hope to remove these caveats in the future so that instancing is faster in all cases.
    • Transform speedup:  results in an over 2x speedup. It applies when the following conditions are satisfied:
      • Nested instancing is not in use (nested instancing occurs when there is for example an instance array location insde an instance source location in the hierarchy)
      • Number of motion time samples on the xform attribute(s) between the instance and the instance source do not match for the given shutter or motion blur time range. Note that any of them having a single sample (not motion blurred) counts as a match, and can still participate in the transform speedup.
      • Time range of the motion on xform attributes(s) between the instance and the instance source do not match. Note that any of them having a single sample (not motion blurred) counts as a match, and can still participate in the transform speedup.
    • Procedural speedup: can result in dramatic speedups if the instance source locations have many child locations. It applies when the following conditions are satisfied:
      • No user data on the instance location (array or pointcloud) is being applied to a specific leaf location on the instance source. E.g. it is possible to apply even up to varying user data to a specific child of an instance source location to customize that particular part of the instance compared to all the rest.  See pointcloud and instance array docs for more information. If you are not using this advanced feature, then the procedural speedup will automatically apply. Note that regular arbitrary attributes which are applied to each instance at once are fine, the procedural speedup still applies.  E.g if you have a color that varies per instance, but not per instance-child, that does not void the speedup.

Bug Fixes

  • ktoa#617 Optimize instancing

  • core#9900 Arnold can raise signals twice if they are handled by the host application
  • core#10621 Artifacts or crashes when interactively changing object's number of transform motion keys or shutter interval
  • core#10511 Artifacts with implicit surface shapes
  • core#10491 Crash due to NaN values in volume displacement
  • core#10516 Crash when passing a null pointer to AiASSLoad()
  • core#9425 Crash when updating the dependency graph after deleting a node
  • core#10395 [GPU] Interactively editing a procedural transform does not update the included lights
  • core#10377 Incorrect motion blur on visible quad and point lights when not using the default shutter
  • core#10483 Large implicit surface shapes can cause slow or hung renders
  • core#10488 Slowdown in stats output when ADP libraries are not found
  • core#10528 [OCIO] Upgrade to bugfix release 2.0.1
  • usd#795 GfMatrix4d attributes are not converted to AI_TYPE_MATRIX parameters
  • usd#778 Procedural doesn't read some animated parameters properly
  • usd#790 Reset the disp_map parameter instead of setting nullptr when there is no displacement
  • usd#768 Custom typed primitives are not written if they already exist

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