ufe.PathString.path returns incorrect path if given path starts with |world

[ika-rporter]

Describe the bug
The ufe.PathString.path function returns incorrect path if the given path starts with |world

Steps to reproduce

1. Open Maya
2. Create this transform hierarchy: |world|foo|bar
3. Select bar
4. Run the snippet below
5. Observe the error when trying to construct a ufe.SceneItem with the path.

import ufe

ufePath_1 = ufe.PathString.path('|world|foo|bar')
ufePath_1.segments[0]
print(ufePath_1)
# |world|foo|bar

ufePath_2 = ufe.GlobalSelection.get().front().path()
print(ufePath_2)
# |world|world|foo|bar

ufe.SceneItem(ufePath_1)
# # Error: pybind11::init(): factory function returned nullptr

We can work around this by remembering to prepend |world to all of our DAG paths it's just ... annoying. Worst case, we change the name of our scene root to something other than world.

Expected behavior
The ufe.PathString.path function should return the correct path

Specs (if applicable):

• Rocky 9
• Maya 2023.3

[seando-adsk]

You should not create a ufe scene item directly by using the constructor. The problem here is that it won't create the derived class which is a Maya scene item. Instead you should always use the Hierarchy.createItem() method.

item = ufe.Hierarchy.createItem(ufePath_1)
print(item)
# <ufe.PyUfe.SceneItem object at 0x0000028CAEB5A1B0>
print(item.path())
# |world|foo|bar

Sean

[ika-rporter]

I think my example was not clear - |world|foo|bar is the DAG path of a node in the scene, not the implicit UFE root. See screenshot.

I created the test scene like so:

cmds.createNode('transform', 'world')
cmds.createNode('transform', 'foo', parent='world')
cmds.createNode('transform', 'bar' parent='bar')

The example in your comment only works if ufePath_1 = ufe.PathString.path('|foo|bar'); otherwise it returns None

[seando-adsk]

Ah sorry I missed from your example. Maya Ufe paths must unconditionally have "world" added as a prefix, regardless of whether they start with "world" or not. This is because in Maya the root node is called "world".

import maya.api.OpenMaya as om
it = om.MItDag()
root = it.currentItem()
om.MFnDependencyNode(root).name()
# Result: world

Sean

[ika-rporter]

So if you have a literal DAG node in Maya named '|world', you need to prepend the root world so you have |world|world|foo|bar? Or change our pipeline so our explicit root is called something else? :)

[seando-adsk]

Unfortunately that is correct. We have a bug logged for that already:
MAYA-131348 - Naming nodes "world" breaks Ufe workflow

In Maya every DAG node is parented to a node called "world". That node is implicit and hidden and Maya knows about it so that is why you don't need to specify it.

In Ufe when dealing with Maya paths we are conditionally added "world" to the path if it is not present. That is the bug. We should be unconditionally adding world. The preferred workaround for you is to not create a node called "world" as the root of your scene. If you add an extra "world" in your paths, if and when we fix the bug, we would break your workaround.

Sean

[ika-rporter]

Understood. I will forward this to our VFX supes and let them decide if we want to rename the root prim in out scenes. Thank you.

[santosg87]

Just a note here, that this fix would require changes on the maya side, so a new version of maya would be needed in order to see the fix.

[santosd]

Going to go ahead and close this one for now, @ika-rporter if anything else comes up, let use know and we can reopened the issue or feel free to log a new issue if it is a different topic.