[MtoA] cross-platform volume file names


The Arnold volume node uses the texture search path, so you don’t have to use an absolute path in the volume filename.

volume_texture_searchpath

So if you need to set up a Maya scene so that the OpenVDB volumes work on any platform, you could put an environment variable in the Texture Search Path

volume_env_var

Just note that support for volume filenames is still a little … rough. You can’t enter an absolute path in the aiVolume Filename box, then enter a texture search path, and expect MtoA to automatically export a relative path. That still needs to be implemented.

For now, here’s what to do:

  • When you first create the volume, load the vdb file and leave the full absolute path in the aiVolume Filename box.
  • Select the grids and set the other volume parameters.
  • Then set the texture search path and strip off the path from the volume file name (leaving just the file name).
  • Now the environment variable will control where Arnold looks for the vdb file.

The Arnold volume node also support environment variables, so you could do this:

volume_env_var_in_filename

But again, once you put the environment variable into the Filename, the path won’t be resolved inside Maya (but it will work when you render).

Tracking down the “error initialzing CLM (9)”


It’s not rocket science, but here’s a little application of the scientific method to technical support.

Observation

The Autodesk licensing system loads AdlmIntRes.xml

I used dtruss on macOS and Process Monitor on Windows to see what files are accessed by the licensing system. (On Linux, I would use strace)

On Windows, the file %LOCALAPPDATA%\Autodesk\Logs\AdlmIntRes.xml is loaded.

procmon_adlmintres

On macOS: $TMPVAR/AdlmIntRes.xml:

56944/0x16208b8:  stat64("/var/folders/vb/1d7zhsx97q7_ddz43nccbyj00000gn/T//AdlmIntRes.xml\0", 0x7FFF55D22F00, 0x0) = 0 0
56944/0x16208b8:  stat64("/var/folders/vb/1d7zhsx97q7_ddz43nccbyj00000gn/T//AdlmIntRes.xml\0", 0x7FFF55D22F30, 0x0) = 0 0
56944/0x16208b8:  open_nocancel("/var/folders/vb/1d7zhsx97q7_ddz43nccbyj00000gn/T//AdlmIntRes.xml\0", 0x0, 0x1B6) = 37 0

On Linux: /var/tmp/AdlmIntRes.xml

Hypothesis

Autodesk licensing will fail if there’s a problem with AdlmIntRes.xml

Testing

  • Delete AdlmIntRes.xml
    No problem. The file is recreated
  • Delete the contents of AdlmIntRes.xml and save the file.
    License authorization fails with the error [clm] error initialzing CLM (9)

compiled against non-compatible Arnold


If you see something like this:

[Arnold]: MAXtoA_Shaders.dll was compiled against non-compatible Arnold 5.0.2.1

it usually means you have an older Arnold trying to load something compiled with  a newer Arnold. There’s two common reasons for this happening:

  • The system PATH includes the location of the older Arnold, so the older Arnold is loaded instead of the Arnold version included with the plugin.
  • The plugin install is messed up, and has the wrong Arnold version in it.

 

[mtoa] Register failed for arnoldAOVChildSelector


If you see this error in the script editor

# Error: Register failed for arnoldAOVChildSelector #

that means your preferred render layer setup is Legacy Render Layers (so MtoA fails to register something that’s used for the new Render Setup).

If you’re not using Render Setup, then you can safely ignore this error.

 

[MtoA] Jittering color with user data


To jitter color with user data, you need to connect an aiUserDataInt to the data input parameter, like this:

mtoa_jitter_userdata

The user data is an mtoa_constant attribute on the shape.  For example, if add an extra attribute named mtoa_constant_jitterID to some shapes, then you can use aiUserDataInt to read the jitterID.

If you want to use the shapes as standins, and be able to set the jitterID in the scene, then export the shapes without the mtoa_constant_jitterID attribute. In the scene, you’ll be able to add mtoa_constant_jitterID to the aiStandin node. The aiUserDataInt node in the ASS file will use that jitterID.

Buying Arnold


get_arnold

 

Annual subscriptions

You get annual subscriptions from Autodesk resellers

You can get Arnold 5-packs at 50% of the usual price, or you can get single Arnold licenses at full price:

Monthly subscriptions

  • You can subscribe for one, two, or three months.
  • Monthly Subscriptions are £60 / €70 / $65 Per Month
  • Monthly subscriptions are available online from solidangle.com

Permanent licenses

Until 30 April 2018, you can still get permanent Arnold licenses. Contact your local Autodesk reseller.

Arnold light_groups and shadow_groups


Light linking in Maya, include/exclude objects for lights in CINEMA 4D, light masks in Houdini, inclusive/exclusive lights in Softimage, they all are translated to light_groups and shadow_groups in Arnold.

Here’s a sphere on a plane, with two area lights (cyan and green).

default

If we add a light_group to the sphere polymesh:

 use_light_group on
 light_group "CyanAreaLight"

then we get this (see below). The sphere is lit only by the cyan area light: the light_group is the lights that affect the object.

light_group_on_cyan
Note that the sphere still casts shadows from the green light, even the sphere isn’t lit by the green light. That’s because there’s no shadow_group, so all lights cast shadows from the object.

If we add a shadow group, so that the light_group and shadow_group are both “CyanAreaLight”, then the sphere is lit by the cyan light only, and casts shadows from the cyan light only.

use_light_group on
 light_group "CyanAreaLight"
use_shadow_group on
 shadow_group "CyanAreaLight"

light_shadow_groups_on_cyan

And finally, here’s the sphere when light groups are on, but there’s no lights in the light group:

use_light_group on
use_shadow_group on
 shadow_group "CyanAreaLight"

light_group_empty