operators using (multiple) alembic nodes and override shaders

[pavelR.]

Just curious if operator shader overrides are supposed to work on multiple objects, namely multiple alembic nodes (using the gpu cache workflow)?

I'm having a hard time to get operators work correctly on multiple nodes, be it alembic nodes or standins.
Sometimes they work/don't-work, depending on how often I hammer the render-update button (without any further changes) and this behavior is directly related to 'parallel_node_init on/off'.

Most often the approaches I tried don't work with 'parallel_node_init off'.

Is the whole selector string parsed as global expression or just the part after the shape-name?

Just curious if something like 'myAlembic*.itemsParent_NULL.someItemPrefix*/*' is possible where 'myAlembic' is the most common name for name/prefix for the alembic-shape-nodes.
(myAlembic1Shape, myAlembic2Shape,...)

Or what would be the correct approach to override shaders on 'certain' nodes?

Doing a '*.(@node == 'polymesh')' expression seems to work but then I can't figure out how to filter by alembic gpu-cache node-name (-part) or by the 'name' and get consistent results when updating the renderer.

(*.(@node == 'polymesh')) and (*.(name == '*standRow*'))

Is the closest I can get but once again it fails if I don't set 'parallel_node_init off' explicitly and just because it worked the last 10 times I hammered the render-update button doesn't mean that this expression is valid.

*update*: doing the same expression in another scene didn't work either.

*update2*: it seems to work with standins but not on alembic nodes (gpu cache nodes)

Any tips on how to get this work using a more 'path-like' syntax? nodeName*/someparent/someChild/*)

[110507]

Hi Pavel,

Recently I've encountered the same issue and was actually about to post the same question. The operator assignments seem to work on multiple instances of the same standIn. However, when I try the same with multiple gpu caches, it only seems to assign the shader to one of them randomly. When I hit the render-update button the assignment switches to another one.

(two shader assignments on multiple instances of same gpu cache)

Please let me know if you find a solution. I'll keep looking for one too and keep you posted.

[110507 · Accepted solution]

It seems the way to make it work is to always have a unique namespace in the translator options of the gpu cache.

This is regardless of the maya namespace the node might have.

Once the alembic translator has a unique namespace you should be able to do the assignments using the 'path-like' selection you suggested:

nodeName*/someparent/someChild/*

Hope this might help.

[pavelR.]

nice!

after some frustrating play-around I picked probably the worst workaround... let me just say that the file-size increased from 5Mb to 350Mb-ish ... imported them all, had some bad experience with regular file-referencing (lost shader connections)..back to the topic...

Setting a unique namespace does seem to work, great finding!

now path-like operator-selectors work!!!: 🙂 🙂 🙂

right*legoman*/legoman_GRP/body*.(@node == 'polymesh')

(I might skip the node-type part, as it works too, just a weird habit.. currently the render-setup does seem to attempt to add material overrides on non-shapes which then results in errors..not related to arnold, seems it's a 2018U3 feature...hence why I try to be as explicit as possible)

I wonder if the arnold-namespace attribute can also be used in some way..
An "easy" way to keep the namespace-string unique is to assign it based on selection via a script.
The attribute name is just 'aiNamespace', so it's rather easy to maintain unique names within a scene.

But again: Amazing that you could figure out a way to use gpu-cache nodes with operators, thanks! (I doubt that I would have ever found a feasible workaround...)

cheers

[orn.gunnarsson]

Is the problem alleviated if you set enable_procedural_cache to false in the options?