[MtoA] The case of the machine that was unable to dynamically load mtoa.mll


In this case, a Windows 7 machine did support SSE4.2, but Maya 2017 still couldn’t load mtoa.mll.

I didn’t get a full Process Monitor log from the client, but I did get a Dependency Walker log, and this case, that was enough.

When you first open a Dependency Walker (dwi) file, it’s easy to focus on the wrong thing. In this case, the missing MSVCR90.DLL (Visual Studio 2008 redistributable) might catch your eye.

dwi_01.jpg

But you can ignore that, because if you take a closer look, you’ll see that MSVCR90.DLL is indeed found and loaded.

dwi_02.jpg

Likewise, you can ignore all these. You’ll almost always see most of those in a Dependency Walker log for Windows 7 and up.

dwi_03

What’s important in this depends log is the warning for AI.DLL.

dwi_04

That warning means that there’s missing functions: MtoA (MTOA.MLL) expects to use certain functions provided by Arnold (AI.DLL), but those functions aren’t there. For example:

dwi_05

And finally, if we click View > Full Paths, we see the reason for the problem:

dwi_06

There’s some older version of Arnold on the system, and that old version is being loaded by MtoA.mll. Most likely, the system PATH includes this location.

With a Process Monitor log, we would have seen right away that ai.dll was being loaded from a non-standard location.

 

[MtoA] Unable to dynamically load : mtoa.mll The specified module could not be found.


I have another, more general, version of this post here. This one is for new Arnold users with Maya 2017.

Here’s what to do if you get errors like this:

// Error: file: C:/Program Files/Autodesk/Maya2017/scripts/startup/autoLoadPlugin.mel line 32: Unable to dynamically load : C:/solidangle/mtoadeploy/2017/plug-ins/mtoa.mll
The specified module could not be found.
//
// Error: file: C:/Program Files/Autodesk/Maya2017/scripts/startup/autoLoadPlugin.mel line 32: The specified module could not be found.

Check if your processor supports SSE4.2

If this is the first time you’ve tried to use the Maya to Arnold (MtoA) plugin, then check whether your processor supports SSE4.2.

Reinstall MtoA

If MtoA used to load, but now it doesn’t, then something happened to the MtoA installation. I’ve seen several cases where DLLs were missing from the MtoA bin folder; most importantly, Arnold itself was missing (Arnold is ai.dll on Windows, or libai.so on Linux, or libai.dylib on OSX).

If you make a backup copy of the MtoA install folder, we can investigate after you fix things by installing MtoA.

Get a Process Monitor log

If a clean install of MtoA doesn’t work (and the computer does support SSE4.2), then “The specified module could not be found.” usually means there’s a missing dependency. Dependency Walker is a decent, if aging, tool for checking out dependencies, but for leaving no stone unturned, I prefer Process Monitor.

The MtoA plugin (mtoa.mll) depends on a handful of files only. Here’s the log of loaded DLLs for a working MtoA:

process_monitor_mtoa

Here’s a quick walkthrough (no audio) of how to get a Process Monitor log:

[MtoA] The renderer ‘arnold’ used by this scene, is not currently available


warning_renderer_not_currently_available

// Warning: file: C:/Program Files/Autodesk/Maya2017/scripts/others/supportRenderers.mel line 64: The renderer "arnold" used by this scene, is not currently available. The "mayaSoftware" renderer will be used instead. //

By itself, this warning doesn’t mean there’s a problem with MtoA or Arnold. The warning means that the MtoA plugin isn’t loaded, so all you have to do is load MtoA:

  1. Click Windows > Settings/Preferences > Plug-in Manager
  2. Scroll down until you see mtoa.mll
    plug-in_manager_mtoa
  3. Click the Loaded and Auto load check boxes.

However, if you get a “Unable to dynamically load : ../mtoa.mll The specified module could not be found.” error, then that’s a different problem.

[Arnold] [MtoA] How to check if your processor supports SSE4.2


This blog post is for Google search to find; I’ve already blogged about the SSE4.2 requirement elsewhere.

If your processor does not support SSE4.2, the Arnold won’t run on your computer. MtoA will either fail to load, or you’ll get a crash whenever you try to render.

To check whether an older machine supports SSE4.2, here’s a few suggestions:

  • Google your processor and “SSE”
    cpu-world is pretty reliable, but I have seen one or two cases where the info was wrong, and SSE4.2 wasn’t really supported by a processor.
  • Windows: Download and run coreinfo -f
  • OSX: Run sysctl -a | grep machdep.cpu.features
  • Linux: Check /proc/cpuinfo

A note about coreinfo:

  • If you see an asterisk (*), then SSE4.2 is supported.
    SSE4.2          *       Supports Streaming SIMD Extensions 4.2
  • If you see a dash (-), then SSE4.2 is not supported.
    SSE4.2          -       Supports Streaming SIMD Extensions 4.2

[MtoA] The curse of pymel.log


PyMEL is great. But…if pymel.log can’t be accessed, any plugin that uses PyMEL will fail to load.

And MtoA uses PyMEL, so every now and again I see a case where MtoA doesn’t load, and you get something like this in the script history:

import arnold
// Successfully imported python module 'arnold'
import mtoa
// Successfully imported python module 'mtoa'
import mtoa.cmds.registerArnoldRenderer;mtoa.cmds.registerArnoldRenderer.registerArnoldRenderer()
# Error: line 1: IOError: file C:\Program Files\Autodesk\Maya2016\bin\python27.zip\logging\__init__.py line 926: 13 #
// Error: Failed to register renderer 'arnold' //
// Error: line 1: initializePlugin function failed (mtoa) //

The important bit is this error:

# Error: line 1: IOError: file C:\Program Files\Autodesk\Maya2016\bin\python27.zip\logging\__init__.py

That error means that PyMELcannot create a log file in your user folder.

By default, the PyMEL log file is created in your Documents folder. For example, if your Windows user account name is Stephen, then this would be the log file:

C:\Users\Stephen\Documents\pymel.log

You need to check the permissions on that log file, or delete it so that PyMel can create a new log file.

Note that the pymel.log file may be a hidden file.

[MtoA] Unable to dynamically load mtoa.mll …The specified procedure could not be found.


If the MtoA plug-in  does not load and you get a “The specified procedure could not be found” error like this:

// Error: line 1: Unable to dynamically load : C:/solidangle/mtoadeploy/2016/plug-ins/mtoa.mll
The specified procedure could not be found.
 // 
// Error: line 1: The specified procedure could not be found.
 (mtoa) //

then there’s a few basic things you need to check first:

  • Does your processor support SSE4.2? As of Arnold 4.2.13.0 (MtoA 1.2.7.0), support for SSE4.2 is required. You won’t be able to load MtoA or use Arnold if your processor doesn’t support SSE4.2.
  • Do you have the right MtoA version for your version of Maya? Major versions of Maya are not binary compatible, so for Maya 2016 you need “MtoA for Maya 2016”.
    And Maya 2016 Extension 2 is not binary compatible with Maya 2016 Extension 1, so if you have Extension 2, you need “MtoA for Maya 2016.5”

If your processor is good and you have the right version of MtoA, then it’s on to basic troubleshooting:

  • Check the environment in Maya. For example, does the PATH include any older versions of MtoA? If you’re on Windows, run the MEL command system(“set”) to get the environment. On OSX or Linux, run system(“printenv”).
  • Check for missing or conflicting libraries. On Windows, you can use Dependency Walker to  check for any conflicts or missing DLLs.

    Download and extract Dependency Walker. Then start it from inside Maya (to inherit the Maya environment). For example, I do something like this:
    system( “start C:/Users/stephen/Downloads//depends22_x64/depends.exe” );

    Then load mtoa.mll.

[MtoA] mtoa missing from Plug-in Manager


If mtoa.mll is not listed in the Plug-in Manager, that means that Maya did not find the MtoA module file (mtoa.mod). And if you try to manually load mtoa.mll, you’ll get errors like this:

// Error: file: C:/Program Files/Autodesk/Maya2016/scripts/others/pluginWin.mel line 781: Unable to dynamically load : C:/solidangle/mtoadeploy/2016/plug-ins/mtoa.mll
The specified module could not be found. // 
// Error: file: C:/Program Files/Autodesk/Maya2016/scripts/others/pluginWin.mel line 781: The specified module could not be found. (mtoa) //

To load MtoA, you need to make sure that Maya finds the MtoA module file.

By default, the MtoA installer puts the mtoa.mod file in the user’s modules folder. For example:

C:\Users\StephenBlair\Documents\maya\2016\modules

If you installed MtoA using one user account, and try to run Maya with a different user account, Maya will not find the module file.

The module file has to be in the MAYA_MODULE_PATH. For example, for the user account “StephenBlair”, here are the default places where Maya looks for modules:

  • C:/Program Files/Autodesk/Maya2016/modules
  • C:/Users/StephenBlair/Documents/maya/2016/modules
  • C:/Users/StephenBlair/Documents/maya/modules
  • C:/Program Files/Common Files/Alias Shared/Modules/maya/2016
  • C:/Program Files/Common Files/Alias Shared/Modules/maya
  • C:/Program Files/Common Files/Autodesk Shared/Modules/maya/2016

If you want MtoA to available to all users, then you could copy mtoa.mod to one of the common locations.