USD: basic support for on_import USD hooks #117822

Merged
Michael Kowalski merged 2 commits from makowalski/blender:usd-import-hooks into main 2024-02-05 14:26:11 +01:00

Added support for defining an on_import() function in
bpy.types.USDHook subclasses. If on_import() is defined
on a given USD hook, it will be invoked in import_endjob().

The implementation closely follows the existing design of
export hooks. USDHook.on_import() takes as an argument
an instance of an internally defined USDSceneImportContext
class which provides an accessor to the USD stage.

Also updated the USDHook documentation with an example
on_import() callback implementation.

Testing

The attached usd_hook add-on provides a basic (somewhat
contrived) example of an on_import() implementation which
creates a Text object in the scene to display the root layer
custom data. Examples of USDZ files with custom data can
be found on the quick-look page.

Added support for defining an on_import() function in bpy.types.USDHook subclasses. If on_import() is defined on a given USD hook, it will be invoked in import_endjob(). The implementation closely follows the existing design of export hooks. USDHook.on_import() takes as an argument an instance of an internally defined USDSceneImportContext class which provides an accessor to the USD stage. Also updated the USDHook documentation with an example on_import() callback implementation. ### Testing The attached `usd_hook` add-on provides a basic (somewhat contrived) example of an `on_import()` implementation which creates a Text object in the scene to display the root layer custom data. Examples of USDZ files with custom data can be found on the [quick-look page.](https://developer.apple.com/augmented-reality/quick-look/)
Michael Kowalski added the
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Michael Kowalski added 1 commit 2024-02-05 03:46:18 +01:00
USD: basic support for on_import USD hooks
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4c7a4788aa
Added support for defining an on_import() function in
bpy.types.USDHook subclasses.  If on_import() is defined
on a given USD hook, it will be invoked in import_endjob().

Also updated the USDHook documentation with an example
on_import() callback implementation.
Michael Kowalski added this to the USD project 2024-02-05 03:46:50 +01:00
Michael Kowalski requested review from Jesse Yurkovich 2024-02-05 04:07:58 +01:00
Michael Kowalski requested review from Brecht Van Lommel 2024-02-05 04:08:21 +01:00
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@blender-bot build

@blender-bot build
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@Matt-McLin for visibility.

@brecht @deadpin I know there are only a couple of days left in Bcon2, but this is a relatively small, localized patch and hopefully can be included in 4.1. However, I would understand if you feel there is insufficient time to review this.

@Matt-McLin for visibility. @brecht @deadpin I know there are only a couple of days left in Bcon2, but this is a relatively small, localized patch and hopefully can be included in 4.1. However, I would understand if you feel there is insufficient time to review this.
Michael Kowalski added 1 commit 2024-02-05 04:42:42 +01:00
Jesse Yurkovich approved these changes 2024-02-05 05:08:44 +01:00
Jesse Yurkovich left a comment
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I'm fine with this going in for 4.1. It seems to work as advertised and the only comments I have pre-date this patch to when hooks were initially added.

  • It seems as through the True/False return value for the hooks aren't really used? Returning False has no real impact it seems.
  • There's a memory leak if a hook is added but never unregistered. This wouldn't typically happen for a real addons but would when running in the script editor or similar. We can fix this up as a separate bug fix.
I'm fine with this going in for 4.1. It seems to work as advertised and the only comments I have pre-date this patch to when hooks were initially added. - It seems as through the True/False return value for the hooks aren't really used? Returning False has no real impact it seems. - There's a memory leak if a hook is added but never unregistered. This wouldn't typically happen for a real addons but would when running in the script editor or similar. We can fix this up as a separate bug fix.
Brecht Van Lommel approved these changes 2024-02-05 12:03:10 +01:00
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  • It seems as through the True/False return value for the hooks aren't really used? Returning False has no real impact it seems.

You are correct. The intent was to future-proof hook implementations to allow for use cases when the return value could matter as the USD hook API evolves. The return value could be helpful for recognizing when the hook function is a no-op so that the IO code can provide fallback behavior (e.g., if a user-specified material conversion hook does nothing, the USD import code could still convert the standard USD Preview Surface material by default). But this is something we can certainly discuss.

Thanks so much for the reviews!

> - It seems as through the True/False return value for the hooks aren't really used? Returning False has no real impact it seems. You are correct. The intent was to future-proof hook implementations to allow for use cases when the return value could matter as the USD hook API evolves. The return value could be helpful for recognizing when the hook function is a no-op so that the IO code can provide fallback behavior (e.g., if a user-specified material conversion hook does nothing, the USD import code could still convert the standard USD Preview Surface material by default). But this is something we can certainly discuss. Thanks so much for the reviews!
Michael Kowalski merged commit ecbf3385c5 into main 2024-02-05 14:26:11 +01:00
Michael Kowalski deleted branch usd-import-hooks 2024-02-05 14:26:13 +01:00
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Reference: blender/blender#117822
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