KtoA introduces Arnold core and is a performance release bringing important optimizations on GPU, toon shading, and imagers. KtoA gains experimental scene import, instancing performance improvements, and better live rendering support for material changes.

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 4.5 support: KtoA supports the upcoming Katana version 4.5 release series. (KTOA-649)
  • ignore_imagers: this option has been added to ArnoldGlobalSettings to facilitate debugging and inspecting renders without any image post-processing applied. (KTOA-618)
  • Experimental import of Arnold data to the scenegraph: a new node ArnoldIn has been added with experimental support for importing any files Arnold understands such as .ass, USD, etc as Katana scenegraph. Currently this is geared towards shape import, but it will also import their material assignments. (KTOA-525, KTOA-673, KTOA-697)
    • Known issues:
      • Standalone materials are not imported (only shader networks assigned to a shape).
      • Some node naming schemes can confuse the Katana scenegraph, such as those generated by C4DtoA.
      • Not all node types are imported properly. For example, there is limited cameras support.
  • Live rendering changes for materials: many more changes to materials are properly updated in live rendering, such as changing shader network topology (adding/removing shader nodes) and changing material assignments to locations. Changes to "global" materials such as operators, imagers, AOV shaders and color manager may not update properly yet, but regular materials are updated properly. (KTOA-22)
  • Instancing performance is improved: instancing via pointcloud or instance array locations now has two fast paths that can be taken (even in combination): transformation fast path, which can happen if the instance source location(s) and the instance location have either simple or matching motion blur timings, and are not part of nested instancing. This speeds up the instancing by 2x. The other is the procedural fast path, which applies as long as the instance doesn't apply arbitrary data to specific sub-locations from the instance source. This scales much better, where complex instance source hierarchies don't cause a slowdown in instancing, and in many existing scenes gives a substantial speedup, potentially many times faster depending on the complexity of the hierarchy underneath the instance source locations. (KTOA-617)
  • Multiple outputs for shaders: these are fully supported in the Katana scenegraph, and will particularly be helpful for both on-disk and inline OSL shaders. (KTOA-652, KTOA-669)
  • OIDN denoiser support: the OIDN denoiser can be accessed via an imager shader, for now. It is not yet available in the ArnoldDenoise node in Katana. (KTOA-634, KTOA-663, KTOA-718)
  • OCIO support and configuration files: KtoA includes and uses by default the OpenColorIO configuration files provided by Arnold core. (KTOA-658, KTOA-667, KTOA-688)
  • Scene units: the meters_per_unit option has been added to ArnoldGlobalSettings to indicate the scene unit size. When using standins (.ass procedurals) with units information, they will be auto-scaled to the units specified in the global settings. (KTOA-657, KTOA-704)
  • Multipart EXR support: multi-part EXRs can be generated by turning on the option for a given output in an ArnoldOutputChannelDefine node. Generally, this won't make any difference unless light group AOVs are being exported to the EXR (which settings are also accessible on ArnoldOutputChannelDefine). Note that disk denoising (using Noice) is incompatible with multi-part EXRs. (KTOA-622)
  • imager_color_curves: this new imager is supported, created as a material and assigned like other imagers to the driver in an ArnoldOutputChannelDefine node. (KTOA-640, KTOA-719)
  • use_existing_tx: this option was added to ArnoldGlobalSettings, where Arnold will pick up any existing .tx files that live next to and correspond to a non-tx file specified as a texture in the image node. (KTOA-690)
  • Scene update script: the scene update shelf script UpdateArnoldNodes has been itself updated to help handle Katana node and parameter changes for Arnold 7.0 and KtoA 4.0. (KTOA-698)

GPU Enhancements

USD Enhancements

  • Katana USD plugins: In Katana versions 4.5 on up, KtoA no longer uses its own implementation of Katana USD plugins, and instead uses the plugins that ship directly with Katana. (KTOA-650)
  • Multiple-frame export: in ArnoldSceneBake, when exporting to USD, additional frames exported are appended.

API Additions

Incompatible Changes

  • pin_threads removed from ArnoldGlobalSettings (KTOA-644)
  • Light linking behavior: in past versions, KtoA has by default had shadow linking follow light linking. Katana convention is to decouple them entirely by default. KtoA now follows this convention, which may result in no shadow linking if scenes only specified light linking previously. (KTOA-647)

Bug Fixes

  • KTOA-557: Variance AOVs not generated for light group AOVs when separate AOVs are requested
  • KTOA-695: ArnoldSceneBake conditional vis ops are not working
  • KTOA-703: KtoA final version component not getting substituted properly
  • KTOA-707: KtoA version number is reported incorrectly to ADP
  • KTOA-713: Don't customize min, target min and target FPS from the core defaults

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