Houdini: Add null node as output indicator when using TAB search

[BigRoy]

Changelog Description

Add visual NULL node as indicator as to what the output will be.

With this PR when adding a Creator instance inside a SOP or COP2 context it now adds a null node as a placeholder for the selection instead of the actual selection.

The null in SOPs:

The publish instance then uses that node instead of 'selection':

This then now also allows to create the placeholder OUT node without having any selection to begin with.

Filter per creator in what node type categories it's shown

Additionally this PR now implements filtering per Creator to decide where it is shown, for example:

• Create Point Cache shows in ROP + SOP context, not in COP2, LOPs, etc. since it's irrelevant there.
• Create Composite shows in ROP + COP2 context, not in SOP, etc. since it's irrelevant there.
• Create Camera (ABC) shows in ROP + OBJ context, not in others since it's irrelevant there.

Add use selection support to Create Composite

Create Composite creator didn't use the selection previously at all - it now does.

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Tl;DR

1. Allow a creator plug-in to specify where it's shown for TAB search completion.
2. Add a feature where if generated in a SOP or COP2 context to add a null node as placeholder.

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Additional info

Here's a screen capture of this PR's functionality:

houdini_tab_create_with_null_node_and_filtering.mp4

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This is an enhancement to the feature added in #4831

Testing notes:

1. Launch Houdini
2. Create relevant publish instances using the TAB menu in the different use cases, e.g. in OBJ, SOP, COP2, ROP networks, etc.

[moonyuet]

i did some testings. They all works as expected. I do have one comment on the point cache and vdb creators although it isn't neccessary at all.
Is it possible to also remove the null node with "out_{family_name}Main" when user deleting the instance through the rubbish bin button?
When I test it and try to delete instance with the button, it seems the null node is still there.

2023-04-20.15-02-11.mp4

[BigRoy]

i did some testings. They all works as expected. I do have one comment on the point cache and vdb creators although it isn't neccessary at all. Is it possible to also remove the null node with "out_{family_name}Main" when user deleting the instance through the rubbish bin button? When I test it and try to delete instance with the button, it seems the null node is still there.

This is one of the reasons I wasn't too sure about this feature. Cleaning it up correctly means we'd need to track that this node was created by that creator and link it to the ROP node, etc. Not impossible, but with quite a few lines of code doable. For example we could add a parameter "created_by" on the null that is itself also linked to the ROP node and then find it through that. However, what if the user still has the ROP node but had changed the SOP path manually to something different than that null. Do we still want to remove it?

I've discussed it with our Lead Houdini FX artist and he said that he'd prefer the null to remain. For him it's more 'convenience' that the node gets created than really being a required part of the ROP node. As such to him it's just a regular null in his network - it just clarifies that a link is being generated to that.

If the feature that the null gets created to begin with is considered like a nice great idea. I'd say let's merge it like this and discuss maybe tweaking it later?

[moonyuet]

i did some testings. They all works as expected. I do have one comment on the point cache and vdb creators although it isn't neccessary at all. Is it possible to also remove the null node with "out_{family_name}Main" when user deleting the instance through the rubbish bin button? When I test it and try to delete instance with the button, it seems the null node is still there.

This is one of the reasons I wasn't too sure about this feature. Cleaning it up correctly means we'd need to track that this node was created by that creator and link it to the ROP node, etc. Not impossible, but with quite a few lines of code doable. For example we could add a parameter "created_by" on the null that is itself also linked to the ROP node and then find it through that. However, what if the user still has the ROP node but had changed the SOP path manually to something different than that null. Do we still want to remove it?

I've discussed it with our Lead Houdini FX artist and he said that he'd prefer the null to remain. For him it's more 'convenience' that the node gets created than really being a required part of the ROP node. As such to him it's just a regular null in his network - it just clarifies that a link is being generated to that.

If the feature that the null gets created to begin with is considered like a nice great idea. I'd say let's merge it like this and discuss maybe tweaking it later?

I see your point and I agree let's get it merge and adjust later if there's issue.

the creator of this PR still works on updating the code

[BigRoy]

Tweaked code a bit based on some notes by @fabiaserra - please do one more test run @moonyuet

[BigRoy]

Ready to merge @antirotor ?