Hi folks,

I have an annoying issue when i export a geo in alembic sequence with changing path attribute to Maya.
I increment the path whit a wrangle node based on frame.
Seams to be Maya keep all the previous path as an empty group.

Any idea ?

Tylius
Hi folks,

I have an annoying issue when i export a geo in alembic sequence with changing path attribute to Maya.
I increment the path whit a wrangle node based on frame.
Seams to be Maya keep all the previous path as an empty group.

Any idea ?

The hierarchy in an alembic must be static. What happens when the path is changed is visibility is animated instead.

Ok I'll try to be more precise with the problem.

In the hip file I sent the aim is to export three or more cube with a unique path attribute.

Here is the prim wrangle code :

That will give me :

frame 1 : s@path = “/cube_01/cube_01_Shape”
frame 2 : s@path = “/cube_02/cube_02_Shape”
frame 3 : s@path = “/cube_03/cube_03_Shape”
…etc

I export my geometry with an Alembic Rop with a frame range from 1 to 3,
path set whit “$HIP/cube_$F2.abc” and “Build Hierarchy From Attribute” checked.
I end up with tree abc file containing one cube with a unique path.

Here is where the problem begin :

Now when I import one of those cube in Maya I should get one unique transform in Maya.
But If I import let say the third exported cube I also get two empty transform from cube 1 and 2.
It is like if the ROP alembic keep's the path of the previous export and iteratively add it to the curent export.

I don't understand this behavior, how can I get rid of this ghost transform ?

Tylius
It is like if the ROP alembic keep's the path of the previous export and iteratively add it to the curent export.

Exactly, the input to the alembic cannot have an animated hierarchy. If it does the output will contain all prims that ever existed, and animate the visibility.

I'm not sure what you're after and why you have the path animated and a frame number in the alembic output. Alembic is normally thought of as a continuous format, not a discrete frame by frame format.

To get what you're after, set the frame range to (1, 1), use a switch on the input, and hit render on the alembic three times, with the output path varying each time. This can be scripted using a shell rop, or maybe with tops.

Thanks for your Explanation jsmack !

The aim behind this simple example was to process à sequence of FBX file (cleaning topology and stuff …).
Unfortunately I didn't find on internet a good explanation to do this with shell rop or TOPs.
It must be simple task to do with TOPs I think but all th examples I found uses wedges and stuff with no clear example to setup an alembic ROP inside TOPS.

Do you have any good ressources to share ?

Ok,

After some headaches understanding PDG workflow with SOP and attributes I made it work.

If it can help some one, here is the hip file.