Release Date

December 13, 2018

This version uses the Arnold core. 




MtoA 3.1.2 is a feature release, including the following improvements:


  • New aiOsl shader, that allows to write inline osl code and use it in a shading tree.
  • Added Sheen parameter in aiToon and in the list of AOVs.
  • Added "Azimuthal Roughness" to aiStandardHair.
  • Added Velvet preset for aiStandardSurface.
  • Fixed crash when assigning a shader to a custom shape procedural.

RenderView / IPR

  • Always add default persp camera to the list of available cameras in ARV.
  • Fixed error "Arnold RenderView is not unique" that could prevent from using ARV when opening an existing scene.
  • Removing objects inside Render Setup collections wasn't refreshed in IPR.
  • Enabling / disabling collections from Render Setup wasn't refreshed in IPR.
  • Deleting an assignment in aiSetParameter wasn't refreshed in IPR.


  • Added arguments to Maya batch render to output Stats and Profile info.
  • Set Overrides were not working on Standins.
  • Upgraded Cryptomatte to 1.1.0 which contains the fix: "Preview AOVs are now always displayed in display drivers, even when preview_in_exr is disabled". 

  • Upgraded OIIO (2.0.1) and OSL (1.10.1).

Incompatible Changes

  • Curves first segment wasn't rendered with the right amount of CVs. This was mostly visible for low samples and is now fixed. Existing scenes might, therefore, render differently.



#3637incorrect sampling of curves at low sample rate
#3656Deleting assignment expressions in set_parameter doesn't trigger an update
#3144IPR doesn't react when disabling/enabling collections in Render Setup
#3350Removing objects inside Render Setup does not refresh the ARV
#3560xgen_procedural: inconsistent evaluation of parameters
#3616Crash when applying shaders to custom shape procedural node
#3624delta flag not being set for the xgen_procedural
#2812Include date and hash in MtoA daily builds
#2841Support OSL node
#3297AOV shaders cause AOV UI re-populating issue
#3591Set override on AiStandin not working
#3623Hide Subdiv Iterations when subdivision is disabled
#3626add sheen AOVs to the main aov list
#3633traslate order of instanced reference objects inconsistent
#3634aiStandardSurface node missing Specular Weight input connection.
#3636[AVP] Ignore Test Resolution
#3639mtoa_constant_ does not work on aiStandIn instances when rendered in ARV
#3644aiMixShader isn't showing textures in VP2
#3645[ARV] "Arnold RenderView is not unique" error
#3655persp camera not available in ARV if it's non-renderable
#3657Add Velvet preset for aiStandardSurface
#3622Add Stats and Profile file output to the Batch Render flags
#3651Expose azimuthal roughness in standard_hair
#3630Add sheen parameters to Toon shader UI
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