[EMSUSD-2138] correct way to use exportMaterialCollections

[willDTF]

I need to export USD from maya with material collection assigned to objects

reading usd-maya documentation, I need exportMaterialCollections and according to this ticket resolved, i dont need to setup materialCollectionsPath argument. so i tried :

cmds.mayaUSDExport( exportMaterialCollections=True, file=usdFilePath, )

this doesn't work, no collection are created. then :

cmds.mayaUSDExport( materialCollectionsPath='/Mtl', exportMaterialCollections=True, file=usdFilePath, )

same result. i tried many variations, without success. The only step forward i've made is with :

cmds.mayaUSDExport( exportCollectionBasedBindings=True, exportMaterialCollections=True, file=usdFilePath, )
material collections is created with the addition of exportCollectionBasedBindings, but no objects are in the collections

cmds.mayaUSDExport( exportCollectionBasedBindings=True, exportMaterialCollections=True, file=usdFilePath,materialCollectionsPath='/Mtl' )
gives the same result that the previous, collections exist but empty

How can I properly export a USD file with material collections assigned ?

thank you

[wallworm]

Sorry I missed this post. We'll investigate and get back to you.

[willDTF]

Hello, I’ve made some progress. Updating to maya-usd last version make it work.
I have a little question, can we force it to be in a subdirectory ? For now it works only if materialCollectionsPath is set to the root Xform

Using ‘/TOM’ as path - Collections exist, objects are members
using ‘/TOM/mtl’ as path - Collections exist, but no objects are members of the collections

Hierarchy is the same in both case

[wallworm]

Thank you for the suggestion. We will look into this.

[santosg87]

@willDTF Not sure if we are missing something, or if this is just a matter of versioning, but testing the workflow on my side with our internal builds, i am seeing collection members as expected, as far as I can tell.

creating a simple Maya scene to mimic yours, then exporting:

import maya.cmds as cmds
usdFilePath = r'''C:\tmp\emsusd-2184-deep-mat-path\tom_new.usda'''
cmds.mayaUSDExport(
    exportCollectionBasedBindings=True,
    exportMaterialCollections=True,
    defaultPrim='TOM',
    rootPrim='TOM',
    rootPrimType='xform',
    file=usdFilePath,
    materialCollectionsPath='/TOM/mtl')

results in a file usd file, with the collections as i would expect:

    def Scope "mtl" (
        prepend apiSchemas = ["CollectionAPI:material:standardSurface2SG", "CollectionAPI:material:blinn1SG", "CollectionAPI:material:standardSurface3SG"]
    )
    {
        rel collection:material:blinn1SG:includes = </TOM/pCone2>
        rel collection:material:standardSurface2SG:includes = </TOM/pCone1>
        rel collection:material:standardSurface3SG:includes = </TOM/pCone3>

is this not the result you are expecting to see?