Release Date

Dec 10, 2019

This version uses the Arnold core. 


Autodesk Network Licensing now requires new license files with an updated 2020 version. Please follow the instructions on this page to generate your license file. More info about Arnold 6 licensing can be found here.

The default installation directory of Mtoa has been modified from this version to be installed within the Autodesk directory. Users will still have full control over installing to any directory of their choice. For example : Linux - /usr/autodesk/arnold Osx : /Applications/Autodesk/Arnold and Windows C:/Program Files/Autodesk/Arnold/


MtoA 4.0.0 is a feature release, that is not binary compatible with 3.1.* versions. It includes the following improvements :


GPU Rendering: GPU no longer in beta. Since the majority of the CPU features are now supported on the GPU, with lots of stability fixes and a good match between the CPU and GPU results, we're boldly removing the beta tag!

aiAxFShader: MtoA has added support for Xrite's AxF file format through a new shader. AxF files can be imported into Maya for use with MtoA via the aiAxfShader.

New aiLookSwitch operator node: This makes it easier for users to add different looks to a procedural asset by automating the practice of adding a switch_operator and merge operators at the root of the procedural operator graph.

Import shader networks: This allows users to import their .ass or .axf shading networks as a Maya shading graph.

Improved viewport representation of Stand-Ins: The representation of stand-ins in the Maya viewport has been improved. Users can now switch between different viewport representations while rendering.

Improvements to IPR: Many improvements have been made overall IPR experience.

Reduced adaptive sampling overhead: The performance overhead from adaptive sampling with large max AA has been substantially reduced

Arnold License Manager The new Arnold License Manager tool, located in the bin folder, allows to easily configure Arnold licensing through a graphical user interface. Users can select and change license type (e.g. Single-user, Network or RLM), sign in to their Autodesk Account, specify license server addresses for network licensing, etc. You can still configure licensing through environment variables, such as ARNOLD_LICENSE_ORDER, solidangle_LICENSE, ADSKFLEX_LICENSE_FILE, in which case they override the settings in the Arnold License Manager configuration file. More information about licensing can be found here.

Alembic Export Command: We have added a dedicated Alembic export command (arnoldExportAlembic) that will export geometry with Arnold options such as subdiv_type, subdiv_iterations, as well as converting mtoa_constant_*, mtoa_varying_* and mtoa_uniform_* custom attributes to the expected Arnold naming and types, it takes the same arguments as the native Maya abcExport command.

Autodesk Standard Surface : We have also added support for Autodesk Standard Surface which is being shipped with Maya 2020. Users can expect this to work similar to aiStandardSurface.

Incompatible Changes

C++11 API: We have raised our minimum C++ requirement to C++11. Compiling with C++03 will likely result in compilation errors.


#3514Support Clic V2
#3650CLIC V2: agent fails on headless Linux with Maya + MtoA Batch Render
#3723Arnold GPU: Computer freezes during scene update for ARV
#3817GPU - Disabling a Light in Light Editor crashes Maya with ARV
#3999ARV missing progress bar when in GPU mode.
#4001Changing CamAA, Diffuse, Spec AA restarts render in ARV but doesn't update values until Update Full Scene.
#4003ARV - refresh render then stop IPR crashes Maya
#4005Arnold Material Viewer in Hypershade using excessive system resources, Maya becomes unresponsive.
#3597Implement Clic2 menus
#3786crash with MayaIO 2019 + MtoA + scene with aiFlat & texture
#3923XGen extensions fail if XGen plug-ins are not loaded first
#4010ARV - change cameras in IPR rendering mode doesn't update until Update Full Scene.
#3338Enable "Export Full Path" by default
#3847Solid Angle logo is still visible on the About screen
#3850Hiding a mesh light crashes the IPR
#3872Hiding/unhiding lights crashes the IPR
#3884Saving an image with 0.001 in the filename crashes eg flakes_scale-0.001
#3919convert 8bit texture to 16 bit exr .tx files
#3931Settings separator to "/" and full paths forces light linking on
#3940procedural UI tree view slow with large object list
#3941use objectpath for aiStandIn viewport preview
#3965create GUI for Alembic export workflow
#3969shader component connections to Maya ramp node not being translated correctly
#3972Fulfill the ODIS requirements for Maya 3rd party installers
#3976Remove obsolete #ifdefs
#3979Bifrost translator should handle greater than 2 GB of data per bif shape
#3985Fix issues in Maya when different renderers are used but MtoA is loaded (output format not saved)
#3988slashes in selection inverted on operator import
#3990Import Operator graph should also import the shaders
#3991Export selected should export the selected shaders too
#3992Change MtoA install folder
#3993AEnewNonNumericMulti.mel has been removed in Maya 2020
#3994[ARV] 3d manipulation wheel causes a crash if no render was started
#4004Memory leak in bif shape translator
#4009Enable C++11 for all builds of MtoA
#4011Remove legacy ABI-breaking code
#4012Use Render API in material viewer
#4013Don't delete alembic procedurals at every IPR change
#4018EXR Distortion from the Beta Forum
#4019EXR Distortion from the Beta Forum
#4022subdiv attributes don't update correctly when shapes have the same name
#4025duplicating aiStandIn duplicates the look attribute
#4027Ensure dcc_name is set for all nodes
#4028parameters with . in the name not displaying in Procedural UI
#3917Add support for Axf shader in Mtoa
#2562Import shader networks from .ass files
#3603Switch to new Render API
#3752Improve the aiSetParameter UI
#3902create our own Alembic Export command
#3937add look variants interface to procedural UI
#3947Support for Autodesk Standard Surface
#3953GPU: API to query if a device is supported
#3977request to add device to snapshot metadata in ARV
#3983Merge all new ADSK standard surfaces viewport changes back into MtoA
#3997create UI for alembic export command
#3998implement new viewport representation API
#4007Bif shape translator should find arnold_bifrost in alternate location



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