In a previous post, I looked at how things could go wrong in the file ~/pymel.log wasn’t accessible. On Windows, this was fairly easy to track down using Process Monitor:

On Mac OS X, I had to use dtruss. For example, I ran this command to trace the syscalls of the Maya Render command:

sudo dtruss -f -t open_nocancel -n Render 2> /var/tmp/mtoarender.log

When the render job failed, I checked the log file, and found this line:

11668/0x35deb: open_nocancel("/Users/stephenblair/pymel.log\0", 0x601, 0x1B6) = -1 Err#13

One important gotcha: if you repeat the render, you won’t find any mention of pymel error in the dtruss output. My guess is that at that point, the Render command ends up going through the file system cache, so dtruss doesn’t see the attempt to find pymel.log.

Here’s a quick summary of the dtruss command I showed above:

• Use sudo to run dtruss, because it needs additional privileges.
• -f tells dtruss to follow any child processes (like mayabatch) launched by Render
• -t filters the trace for open_nocancel system calls
• -n tells dtruss to trace the process named “Render”
• 2> /var/tmp/mtoarender.log redirects the dtruss output to a file

When you enable file logging, it can seem a bit of a mystery where the .log files end up. You may find log files in different folders of your project, like the scenes folder, or the sourceimages folder.

Here’s how it works.

• If the MTOA_LOG_PATH environment variable is set, the log files are saved to the folder specified by MTOA_LOG_PATH.
• If MTOA_LOG_PATH is not set, the log files are saved in the current workspace directory (in MEL, that’s workspace -q -directory). In other words, the log files are saved to last place you went with the Maya file browser. If you haven’t used the file browser yet, the log file is saved in the root folder of the project.
• If you click the folder icon beside the Filename text box, you can choose where the log files are saved.

Note that the log files will always include the frame number, so you’ll get arnold.1.log, arnold.2.log, and so on.

The technical reason for a “No ISV servers to start” message is that that RLM could not read the ISV line from the license file.

So, for example, if you somehow save the license file as a binary file that looks like this:

then you’ll get No ISV servers to start, because obviously there’s no ISV line in that file.

Note: You’ll also see The hostname in the license file(s) may be incorrect, but that warning can always be safely ignored.

05/14 09:17 (rlm) 
05/14 09:17 (rlm) WARNING: No license file for this host (StephenBlair-PC)
05/14 09:17 (rlm)          The hostname in the license file(s)
05/14 09:17 (rlm)          may be incorrect
05/14 09:17 (rlm) 
05/14 09:17 (rlm) License files:
05/14 09:17 (rlm)     arnold_eval_90b11c647d93_20150514.lic
05/14 09:17 (rlm) 
05/14 09:17 (rlm) RLM License Server Version 11.2BL2

	Copyright (C) 2006-2014, Reprise Software, Inc. All rights reserved.

05/14 09:17 (rlm) License server started on StephenBlair-PC
05/14 09:17 (rlm) Server architecture: x64_w2
05/14 09:17 (rlm) License files:
05/14 09:17 (rlm)     arnold_eval_coffee0000_20150514.lic
05/14 09:17 (rlm) 
05/14 09:17 (rlm) Web server starting on port 5054
05/14 09:17 (rlm) Using TCP/IP port 5053
05/14 09:17 (rlm) ... adding UDP/IP port 5053
05/14 09:17 (rlm) (No ISV servers to start)

The Arnold log is important, not just for troubleshooting and getting help from us at Solid Angle, but also for understanding what’s going on when Arnold renders your scene.

But, first things first: where’s the log? The Arnold log is output to the Cinema 4D Console:

To open the Console, click Script > Console.

You can set the verbosity level in the Render Settings > Diagnostics. By default, the verbosity level is Warnings, but by increasing it to Info, you’ll get the % done log entries. You can also send the log to a file (good for logging support cases!).

This error

ERROR   | [mtoa] [xgenTranslator] Could not find xgen_procedural in search path $ARNOLD_PLUGIN_PATH

happens only when MtoA is first loaded, and it can be safely ignored. It doesn’t cause any problems when you render, and MtoA loads the XGen procedural from the MtoA procedurals folder.

The error is a consequence of how MtoA searches folders when it loads extensions. If you really need to get rid of the error, you can try copying the xgen_procedural library to the MtoA shaders folder.

These warnings mean that Arnold can connect to the RLM license server, but Arnold cannot connect to the solidangle ISV server:

00:00:12 14MB WARNING | [rlm] * Communications error with license server (­17)
00:00:12 14MB WARNING | [rlm] * Connection refused at server (­111)

Usually the problem is that the solidangle ISV server is not running.

You can check the status of the solidangle ISV server with RLM Web Admin. I like the get the RLM diagnostics (Diagnostics > Run Diagnostics) from RLM Web Admin and review that.

In rare cases, the problem is something else, such as:

• Some sort of network connection problem. For example, I recently had a case where we would get these warnings when we used the IP address of the license server in solidangle_LICENSE. But as soon as we switched to using the hostname, everything worked.
• Another RLM instance is running and listening to port 5053, and that instance doesn’t have a solidangle ISV running. I heard about this second-hand, from a customer; I didn’t see it with my own eyes and I don’t know how it’s possible. You can have multiple RLM instances running, but each instance has to have a different port otherwise you get ” “Port 5053 in use, waiting…” messages and the second RLM won’t start.

C4DtoA requires R17.032

I’ve had a number of cases where people had earlier versions of C4D R17 and couldn’t use C4DtoA. That’s because C4DtoA was built against the C4D R17.032 SDK.

Any time you see “node … is not installed” and “unresolved reference” warnings when you try to kick an ASS file exported from Maya, the problem is missing MtoA shaders.

00:00:00 18MB WARNING | [ass] line 259: node "MayaFile" is not installed
00:00:00 18MB WARNING | [ass] line 288: node "MayaShadingEngine" is not installed

00:00:03 23MB WARNING | [ass] line 238: pSphereShape1.mtoa_shading_groups: unresolved reference to 'aiStandard2SG'
00:00:03 23MB WARNING | [ass] line 137: aiSkyDomeLightShape1.color: unresolved reference to 'file1'
00:00:03 23MB WARNING | [ass] line 188: pPlaneShape1.shader: unresolved reference to 'aiStandard1SG'
00:00:03 23MB WARNING | [ass] line 197: pPlaneShape1.mtoa_shading_groups: unresolved reference to 'aiStandard1SG'
00:00:03 23MB WARNING | [ass] line 229: pSphereShape1.shader: unresolved reference to 'aiStandard2SG'

When you render with kick, you need to specify the location of the MtoA shaders. You can do this several ways:

• Set the ARNOLD_PLUGIN_PATH environment variable. For example:

  export ARNOLD_PLUGIN_PATH=/home/render/solidangle/mtoa/2016/shaders

  set ARNOLD_PLUGIN_PATH=C:\solidangle\mtoadeploy\2016\shaders

• Use the kick -l flag to specify the MtoA shader location.
• In Maya, set the Shader Search Path in the Arnold Render Settings, then export the ASS file.

Shader nodes must have unique names.

So if you’re using standins, each standin ASS file has to have unique shader node names. Otherwise you’ll get unexpected results when you render, like all standins having the same shading, or some “flickering” in animation if the order of standin loading changes.

In the Arnold log, look for “node name already in use” warnings:

WARNING | [ass] standin_01.ass line 50: node name "aiStandard1SG" already in use
WARNING | [ass] standin_01.ass line 58: node name "aiStandard1" already in use
WARNING | [ass] standin_01.ass line 118: node name "file1" already in use
WARNING | [ass] standin_01.ass line 147: node name "aiNoise1" already in use

If each standin should look different, you need to have unique shader names in each ASS file. If you’re using MtoA, that includes the name of the SG node (for example, aiStandard1SG).

Reason #35 why you should check the Arnold log

In this case, a scene that used to render yesterday, now just resulted in a blue render view, like this:

Anytime the render view doesn’t update when your render, you can be fairly sure there’s some ERROR in the Arnold log.

In this case, the problem was a broken path to the IES file used by a photometric light. In the Arnold log, there was this ERROR:

00:00:04 870MB ERROR | [photometric] can't open C:/Assets/IES/example.ies

It’s easy to say “check the log”, but where do you find the log? It’s not like there’s a nice, color-coded button (red for error) on the render view UI that will pop up the log for you.

• On Windows, you should see the Arnold log in the Output Windows. However, I find that this happens only when I start Maya from the command line. If I start Maya from the Windows Start menu, the Arnold log messages don’t show up in the Output Window. So I have to enable file logging, and check the log file.
• On OSX and Linux, you’ll also have to enable file logging, unless you start Maya from a terminal.

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.

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.

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.

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

// 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
   
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.

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.

• The latest MtoA version is available at solidangle.com/arnold/download
• Previous versions are available at solidangle.com/arnold/download/archive

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:

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

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.

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

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

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

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:

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

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.

In this case, a client complained that Arnold wasn’t rendering Yeti fur. I asked him to try with a simple sphere, and to send me the log (at verbosity level Warnings + Info).

This what I was looking for:

00:00:00  1222MB         | there are 1 light and 2 objects:
00:00:00  1222MB         |       1 persp_camera
00:00:00  1222MB         |       1 skydome_light
00:00:00  1222MB         |       1 utility
00:00:00  1222MB         |       1 lambert
00:00:00  1222MB         |       1 driver_exr
00:00:00  1222MB         |       1 gaussian_filter
00:00:00  1222MB         |       1 polymesh
00:00:00  1222MB         |       1 list_aggregate
00:00:00  1222MB         |       1 MayaShadingEngine
00:00:00  1222MB         |       1 renderview_display

So, what’s there? Well, the important thing is not what’s there, but what’s not there.

There’s no procedural. If Yeti was installed properly, there would a procedural node. The Yeti extension exports a procedural node when MtoA translates the scene.

That means the PATH or MTOA_EXTENSIONS_PATH wasn’t set up properly. I always use the Yeti module file for that.

Or, “Understanding the Arnold log, part 23”

In this case, a client had very low (15%) CPU usage for a render. We got the Arnold log, and here’s the interesting part:

00:01:44  856MB   | OpenImageIO ImageCache statistics (0000000025850F20) ver 1.5.24
00:01:44  856MB   |   Images : 3 unique
00:01:44  856MB   |     ImageInputs : 299 created, 2 current, 3 peak
00:01:44  856MB   |     Total size of all images referenced : 192.4 MB
00:01:44  856MB   |     Read from disk : 12.0 GB
00:01:44  856MB   |     File I/O time : 45m 41.5s (48.1s average per thread)
00:01:44  856MB   |     File open time only : 0.0s
00:01:44  856MB   |   Tiles: 711523 created, 559 current, 640 peak
00:01:44  856MB   |     total tile requests : 249379431
00:01:44  856MB   |     micro-cache misses : 3353694 (1.34482%)
00:01:44  856MB   |     main cache misses : 711523 (0.285317%)
00:01:44  856MB   |     Peak cache memory : 10.0 MB
00:01:44  856MB   |   1 not tiled, 1 not MIP-mapped
00:01:44  856MB   | -----------------------------------------------------------------------------------
00:01:44  856MB   | performance warnings:
00:01:44  856MB   | Rendering utilization was only 15%. Your render may be bound by a single threaded process or I/O.
00:01:44  856MB   | -----------------------------------------------------------------------------------

• File I/O time seems a bit high for three textures and a render that took less than 2 minutes
• main cache* misses is pretty high. Normally you expect something less than 0.01%.

  0.285% means that texture tiles are loaded from disk (instead of from the in-memory texture cache) once out of every 350 texture lookups. That’s a little high.

  * The main cache is the cache of 64×64 texture tiles loaded from disk into the texture cache.

• Peak cache memory is 10.0 MB !!! That explains the main cache misses: the texture cache is really, really small.

Other clues to the too-small texture cache size:

• Read from disk is 12 GB but the total size of all images referenced is just 192.4 MB, and the peak cache memory was just 10.0 MB
  So the same texture data is constantly being unloaded from the cache and reloaded from disk.

The solution? Increase the size of the texture cache. The current default is 2048, which should be good in most cases.

If you get this UnicodeEncodeError when you render

# Error: line 1: UnicodeEncodeError: file C:\Program Files\Autodesk\Maya2016\bin\python27.zip\encodings\utf_8.py line 16: ascii #

it’s probably because because the project folder has a special character in the name (for example, an accent mark like é).

If that’s not it, then we’d need more context (hint: everything else that is logged in the script history).

For a project name with a special character, you’ll see something like this in the script history:

file -f -save -options "v=0;";
// C:/maya/projects/New_Projéct/scenes/blank.mb //
# Error: line 1: UnicodeEncodeError: file D:\Program Files\Autodesk\Maya2017\bin\python27.zip\encodings\utf_8.py line 16: ascii #
# Error: line 1: UnicodeEncodeError: file D:\Program Files\Autodesk\Maya2017\bin\python27.zip\encodings\utf_8.py line 16: ascii #