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KtoA 4.3.2 now available...

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KtoA 4.3.2 now available...

22 May 2024

KtoA uses Arnold and is a feature release.


Katana 4.5 and 5.0 compatibility

Katana 4.5v3 and 5.0v3 introduced a change that affects the Arnold USD plugins support in Katana. This release of KtoA supports those Katana versions or newer within their release series. Katana 4.5v1, 4.5v2, 5.0v1, and 5.0v2 are not supported by this KtoA release.


  • Toon tone-mapping: You can now drive the hue and saturation of tonemapping in the toon shader. The toon shader has four new parameters that complement the existing value-based tonemapping parameters. The connected shader's U coordinate drives direct light hue and the V coordinate drives saturation, which enables textures like those below to map the toon shader's response to colored lighting (Note: make sure to set the image's wrapping mode to clamp and filter to closest for best results) (ARNOLD-10687). These toon parameters include:

  • Better volume denoising: Denoising volumes now produces better results. The changes in how volume albedo is computed help the denoiser to keep more details. Ringing artifacts when objects are viewed against the background are also reduced, and a new N_denoise AOV fixes some denoising artifacts visible in low-AA renders. (ARNOLD-14936, ARNOLD-13071)
  • Many-lights support for light linking: Global light sampling is now applied per group of lights linked to a shape. That can improve rendering performance for scenes with light linking. The ALab scene now renders twice as fast when you use Global Light Sampling. (ARNOLD-14985)
  • Improved Standard Hair on GPU: The GPU renderer now supports the extra_depth parameter. This enables accurate rendering of blond or bright-colored hair without raising GI_specular_depth.
  • Improved volume albedo AOV: Volume albedo values are now more physically-based. This improves volume denoising and any LPE AOV using volume albedo is now much more useful for compositing. For backwards compatibility, you can set the new global option legacy_volume_albedo to true. (ARNOLD-13071)
  • Bake displacement and subdivision to mesh: The ArnoldSceneBake node can bake subdivided and displaced polymesh geometry to disk. (KTOA-1002)
  • Improved OSL interoperability: The color4, color2, vector4, vector2, and matrix33 are now supported as output types of OSL shaders when connected to Arnold shaders. Additionaly, Arnold shaders that output RGBA or Vector2 types can now be directly connected to OSL shader color4 and vector2 input parameters. Those features make it easier to mix Arnold and MaterialX standard library shader nodes. (ARNOLD-1398 ARNOLD-14692)
  • ArnoldOutputManager improvements: The ArnoldOutputManager node now can edit dynamic filter and driver parameters. (KTOA-998)
  • Update OpenVDB to version 11.0: Arnold now uses the latest OpenVDB library. For the list of changes between OpenVDB version 7.1.1 and version 11.0, see the release notes. (ARNOLD-11217)


USD Enhancements

  • Cylinder lights - Cylinder lights are saved as UsdLuxCylinderLight primitives - usd#1894

API changes

  • Geometry baking API: You can now bake subdivided and displaced geometry. You can save the baked geometry either in another universe or you can change the geometry in-place in the same universe. Typically, you would bake geometry by looping over scene nodes with AtNodeIterator. Currently, geometry baking applies to polymesh nodes only.(ARNOLD-2815)

     AI_API AtNode* AiNodeGetProcessedGeometry(AtNode* source_node, AtUniverse *dest_universe);

Incompatible Changes

  • Save usdz files to a usdz_tx folder: Previously when reading a .usdz file, any generated .tx files would be saved to a folder named <usdz_filename>.tmp. The .tmp extension may have led users to remove this folder prematurely, resulting in extra work the next time the usdz was rendered. These files will now be written to and read from a folder name <usdz_filename>.usdz_tx. (ARNOLD-14999)
  • Improved volume AOV: The volume albedo AOV and LPE scattering event has been improved. For backwards compatibility, you can set the new global option legacy_volume_albedo to true. (ARNOLD-13071)

Bug Fixes

  • ARNOLD-8165 - Crash when curvature, ambient occlusion, or round corners is used in displacement
  • ARNOLD-14551 - Add log notification when FIS is enabled
  • ARNOLD-14590 - Very bright lights, such as the sun, are not properly occluded by dense volumes
  • ARNOLD-14970 - [GPU] Rare “stack overflow exception” crash with OSL shaders
  • ARNOLD-14995 - [GPU] Crash when attempting to render a Bifrost volume
  • ARNOLD-14998 - Rare crash in Windows when texture_searchpath contains a root directory
  • ARNOLD-15015 - Profiler data is lost when other universes are destroyed
  • ARNOLD-15030 - GPU renderer and denoiser imagers incorrectly overriding FIS parameters set in options
  • ARNOLD-15040 - AiTextureLoad crashes with textures that use subimages as mipmaps
  • usd#1900 - Fix transform hierarchies for Arnold non-xformable primitives
  • usd#1903 - USD Writer should skip materials when the shader mask is disabled
  • usd#1906 - Fix light filters assignment order in the render delegate to make it consistent with the procedural.
  • usd#1912 - Procedural interactive updates don't consider primitives visibility

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.
  • x86-64 CPUs need to support the SSE4.1 instruction set.
  • GPU rendering and Optix denoising work on Windows and Linux only, and require an NVIDIA GPU with the Maxwell architecture or later.
  • Katana 4.5v3 or newer, Katana 5.0v3 or newer, Katana 6.0v1 or newer, Katana 6.5v1 or newer, or Katana 7.0v1 or newer.

// Stephen Blair
// Arnold Renderer Support

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