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Andrew Wilkins avatar image
Andrew Wilkins asked

Import Operator Graph

Good day,

Digging into some operators for DCC portability of LookDev, I've noticed something with the "Import / Export Operator Graph" features.

After exporting operator selection and using the "Export Assigned Shaders" feature in Maya—we of course get the operators & shaders stored in the ASS file as intended.


export-op-graph.jpg


On importing back into Maya using the " Import Operator Graph" we get the shaders re-built in the scene which is great + the operators.

On importing this same ASS file (shaders built and operators created in Maya) into Houdini using the Arnold output—" Import Operator Graph" the shaders are not-rebuilt in Houdini?
We also don't get the operators imported?

In Houdini the "Export Assigned Shaders" feature also seems to be missing?

hou-import-operators.png


aiIncludeGraph and MatX don't provide access to the shader in the scene at the back-end of the pipe (Lighting) for adjustments.
So to me it's preferable to have the shader re-built in the scene on importing and those shaders referenced by the newly imported operators.

Summary:

  • For cross-DCC portability, why are the shaders not being re-built from the ASS file in Houdini like it does in Maya? And why aren't the operators imported?

  • Can't the shaders be exported alongside the Operators from Houdini to use in Maya?
    • I know there is the Houdini Arnold "Export / Import Materials"—but that would be a separate ASS file which doesn't store operators or shader assignments. It doesn't seem to be a combined export for easy import into another DCC.


Regards,
Andrew


Maya:
Maya: 2022
MtoA: 4.2.1
Arnold: 6.2.0.1

Houdini:
Houdini: 18.5.462
HtoA: 5.6.0.0
Arnold: 6.2.0.0

mtoahtoaoperators
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Stephen Blair avatar image
Stephen Blair answered

Arnold ROP > Import Operator Graph imports the operators connected to the options node.

So in Maya, you have to export the options and operators.

HtoA doesn't import operators on procedurals.

And Import Operator Graph does not create the shaders referenced by operators.

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Thank you Stephen, I'll do a bit more testing and follow-up if I have any additional questions
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Andrew Wilkins avatar image
Andrew Wilkins answered

Hey again Stephen, thanks for the reply! :)


Okay so, for example:

LookDev done in HtoA and brought into Maya:
(per asset)

  1. Hou: Export all shaders as an "ASS" file
  2. Hou: Export Operator Graph (Assignments / Properties) as another "ASS" file
  3. We get 2 separate files to import into Maya
  4. Maya: Arnold > Shaders > Import Shaders
  5. Maya: Arnold > Operators > Import Operator Graph
  6. Maya: Connect Operators Graph to "Standin" asset. (aiMerge - named per "look") - which then the aiSetParameter operators reference the shaders in the Maya scene


TBH, I was hoping that one could simply go "Arnold - Export" in Houdini and "Arnold - Import" in Maya or vice-versa and have everything working.
(shaders, assignments & properties) with the shaders existing in the DCC


"So in Maya, you have to export the options and operators."

I would assume the artist would set-up the LookDev (Looks, SetParameter assignments / properties) on the aiStandin (in Maya for example) and export "Selection" from there?
(obviously automated on publish per asset)

So exporting the "options" or we're talking about "Scene Graph" export option instead of selection?
And that would import correctly into Houdini "ROP"?


"HtoA doesn't import operators on procedurals."

Yeah this unfortunately doesn't seem as fleshed out as the current approach in Maya

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Nope, Scene Graph exports the operators and shaders only (as I expected).

I had to use Arnold > Scene Export (or File > Export) and select options, operators, shaders

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