Load VDB to Redshift: Create and assign a RedshiftStandardVolume material on load

[BigRoy]

Changelog Description

Create and assign a RedshiftStandardVolume material on loading VDB to Redshift.

This also fixes an issue where on load Redshift would sometimes report a warning that the file does not exist (because Maya still had to initialize the useFrameExtension behavior). This PR now directly forces maya to evaluate that and avoids the warning like:

// Warning:  [Redshift] Failed to find volume file C:/projects/ayontest/asset/char_hero/publish/vdbcache/vdbcacheMain/v005/ynts_char_hero_vdbcacheMain_v005.0001.vdb. Volume will be empty

Additional review information

The option can be disabled on the Load action via the option box on the action itself.

This avoids the issue that when loading the VDB that by default it would NOT display in the render - usually Redshift would log that it had no shader and hence be skipped. Now, a shader is created and assigned and the field channel to use is guessed from the available grid names: use density if available, otherwise use first grid name which may save time as to debug "why doesn't it render?" and typing a valid channel name manually by the artist.

It does introduce potential follow up issue:

1. These materials are unmanaged (not in the container currently), and removing the Volume from the scene via scene inventory will keep the material around. If we were to add it to the container we get to the downside that the material may be used by the artist for other objects in the scene. The question is, which of the two behaviors would be worse?
2. Each load of a Redshift Volume would now generate a new shader in the scene. It may be unwanted.

---

The creation will also be logged:

// ProductLoader : Created RedshiftStandardVolume: 'rsStandardVolume12' using channel 'surface'

Testing notes:

1. Load Volume to Redshift.
2. With the material applied it should directly be able to render.

[LiborBatek]

I have used tray publisher to ingest some VDB cache file from internet (Embergen)

and Im getting this error once using Ayon>Load VDB (Redshift) I guess its because it has just density grid inside not color

Traceback (most recent call last):
  File "C:\Users\lbate\AppData\Local\Ynput\AYON\addons\core_1.0.13\ayon_core\tools\loader\models\actions.py", line 740, in _load_representations_by_loader
    load_with_repre_context(
  File "C:\Users\lbate\AppData\Local\Ynput\AYON\addons\core_1.0.13\ayon_core\pipeline\load\utils.py", line 325, in load_with_repre_context
    return loader.load(repre_context, name, namespace, options)
  File "c:\Work\REPO\ayon-maya\client\ayon_maya\plugins\load\load_vdb_to_redshift.py", line 94, in load
    self._create_default_redshift_volume_shader(volume_node)
  File "c:\Work\REPO\ayon-maya\client\ayon_maya\plugins\load\load_vdb_to_redshift.py", line 175, in _create_default_redshift_volume_shader
    cmds.connectAttr(f"{material}.outColor",
RuntimeError: The source attribute 'unknown1.outColor' cannot be found.```



once assigned the shader manually and inspect the asset (data is ok)


![Screenshot 2025-01-17 103416](https://github.com/user-attachments/assets/d5574597-8928-4916-9ffd-6b0b3e521cc6)