Release Date

March 20, 2019

This version uses the Arnold core and includes the beta version of Arnold GPU


Important information about Arnold GPU (beta)


Download MtoA for Maya 2017, Maya 2018 and Maya 2019 here:


MtoA 3.2.0 is a major feature release, which is binary compatible with 3.1.* versions.

It includes the following improvements :

GPU Rendering (BETA)

You can now switch between CPU and GPU render devices interactively and expect visually similar results. NVIDIA® GPUs from Turing™ to Maxwell™ architectures are supported, and Arnold will take advantage of multiple GPUs, NVLink™ and NVIDIA® RTX™ hardware accelerated raytracing if available. Note that due to beta status of GPU rendering, a number of features are missing, performance is not final, and use in production is not advised. We plan to gradually improve this in subsequent releases and would appreciate your feedback. For a complete description of requirements, features and caveats, see Getting Started With Arnold GPU.

Improved Sampling

  • Improved adaptive sampling: Adaptive sampling is now much more effective and predictable than before.
  • Improved skydome sampling: Skydome light's sampling has been improved, in particular in darker areas. Note that existing scenes which were adjusted with previous versions of Arnold will now need to lower down the number of light samples for an equivalent result.
  • Faster sample generation: Scenes with a high number of AA and light samples could take a very long time to start rendering. This is now much faster (some use cases went from 11 minutes to a fraction of a second, before the render starts).

Improved Shading

  • Microfacet multiple scattering: The GGX microfacet BSDF used in the standard_surface shader has been improved to account for multiple scattering between the microfacets, which is more physically correct and reduces energy loss on reflection, especially at higher roughness settings. The reflection from rough metals, in particular, will be significantly brighter and more saturated as a result.


Without microfacet multiple scattering

With microfacet multiple scattering

  • Improved randomwalk SSS: A new SSS mode randomwalk_v2  has been added that scatters more accurately and deeply through highly-transparent/optically-thin objects, which produces SSS with more saturated colors around fine surface detail and heavily backlit regions of an object

  • Smart opaque: When using builtin shaders, Arnold will now automatically set the opaque parameter in the shapes. Setting transparency only in the shaders will now be enough (exceptions are curves / points using min_pixel_width). Custom shaders can support this feature by setting metadatas opacity_term and transparency_term in the shaders.
  • Improved bump and normal_mapping: bump and normal mapping now correct for non-physical shading normals (eg. extreme values) while preserving detail.
  • Anisotropy controls for coat in aiStandardSurface
  • Support for negative "Transmission Extra Roughness" in aiStandardSurface
  • New aiUvProjection shader allows to do spherical/cubic/ etc.. projections on a surface
  • Exposing Arnold shaders aiCameraProjection, aiRampRgb, aiRampFloat, aiRgbaToFloat

Visible Lights

StandIns & gpuCache workflow improvements

  • New UI for shader assignments and overrides using Arnold operators: A new UI in Stand-ins and gpuCache allows to introspect nodes, assign shaders to specific elements, override parameters, etc... in a user-friendly way. It will allow to create and edit operators attached to the Stand-in, that will, therefore, be portable across scene references. Check the video showing how to use Operators and assignments with alembic files.

  • Standins can now load alembic files

  • Show selected item in the viewport: While introspecting a Stand-in content, selecting items will highlight them in the viewport. Picking in the Arnold RenderView will also select the corresponding item.
  • New workflow for Standin's proxy geometries in the viewport: A new parameter ignoreGroupNodes will skip all the nodes below the Stand-in hierarchy for rendering. The desired proxy geometries just need to be parented to the Stand-in, and they will only appear in the viewport when this parameter is enabled.
  • Subdivision creases supported in Alembic

Export Shading trees as MaterialX files

New menu Export Selection to MaterialX allows exporting the selected shading trees to a materialx document. It's also possible to append several looks to a single mtlx file and then to switch between both in the materialx operator. Geometrie's properties (subdivision settings, etc...) can also be baked to the file.


  • Added option to Export/Import operator graphs: New menu Export Operator Graph allows to export an operator graph to a .ass file (either the selection or the scene's graph). It's then possible to import it back to Maya, or even to another DCC.
  • New include_graph operator: Includes an operator graph that was previously exported to .ass.


  • Improved workflow for motion vectors AOV: new attribute Instantaneous Shutter in the motion blur settings allows getting correct motion vectors AOV while rendering a still image. The shutter range will now be taken into account in the AOV.
  • Faster .ass file writing: Writing to .ass, especially over Windows networks, can be dramatically faster (up to 51x reported)
  • Faster OSL UDIM texture reads: Reading UDIM textures in OSL is now much faster (up to 10x reported)
  • Disabled Swatch rendering by default, to avoid non-necessary excessive slowdowns
  • Exposing "autobump visibility" in meshes to solve artifacts for objects appearing through sharp reflections/refractions.
  • Updated to OIIO 2.1.0


  • Fixes on triplanar used for displacement.
  • Adaptive sampling was being reset to OFF during IPR updates.
  • Interactivity optimizations when IPR is stopped.
  • Texture repeat wasn't working with custom UV sets.

Incompatible Changes

  • Default specular_roughness in aiStandardSurface is now 0.2. Existing scenes that had left this parameter to its default value might now look different.
  • Changes in skydome sampling require to lower down the skydome samples on existing scenes for an equivalent result and render times. For the same settings as before, the result will be less noisy but up to 30% longer.
  • Removed support for NVIDIA Kepler GPUs.
  • Specular AOV: The sheen component has been removed from the specular AOVs.
  • Removed SSS on curves.


#3702User data on xgen_procedural node is not used when you render Maya scene file
#3722texture repeat not working with file node and custom UV set
#3504another uvSet is rendered if UV Shell was deleted
#3672Remove warning about "maya" driver not found
#3678Update MFnDependencyNode::findPlug signature
#3685Normal map is incorrect with flipped UVs
#3687MayaShadingEngine exported with pxfHair
#3690Crash with custom set nodes
#3694No uint in AOV type list
#3705Xgen Splines (interactive) doesn't export matrix during interactive sessions
#3731[ARV] adaptive sampling reset during IPR iterations
#3732Small interactivity optimizations when IPR is stopped
#3303Disable render swatches by default
#3677add curve basis override to gpuCache interface
#3526Improve overrides for gpuCache and standins
#3601Export shading trees as materialx document
#3659Scene assembly representation not rendering in Batch / Ass Export
#3676Expose include_graph operator
#3681Allow exporting selected operator graph
#3696Allow Stand-ins to load alembic files
#3698Show Stand-in selected item in the viewport
#3709Expose pre-populate GPU cache
#3728Disable shaders motion blur by default
#3729Expose new option to render with an instantaneous shutter
#3736Expose ramp_rgb and ramp_float
#3739Expose and Export render_device_fallback
#3742Allow hiding geometry below the hierarchy of a Stand-in
#3743Expose autobump visibility
#3509Export Maya's Projection shader as Arnold native shaders
#3621Export lookdevkit as Arnold native shaders - Part 2
#3674Switch operators input in procedurals to rely on the core parameter
#3691Convert MayaGammaConvert shader
#3703Convert MayaSamplerInfo Shaders to Arnold Native Shaders
#3708Convert Maya's ramp as Arnold ramp_rgb
#3710Convert Maya Contrast as Arnold shaders
#3711Remove Maya displacement shaders from MtoA
#3714Remove MtoA's Anim shaders
#3715Remove MtoA's write AOV shaders
#3716Convert Maya remap shader to Arnold native shaders
#3720Convert RenderSetup shader to Arnold native shaders
#3721Export MayaImagePlane using Arnold native shaders
#3725Convert HairPhysical shaders to use Arnold core shaders
#3733Label GPU supported things using metadata



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