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fix instancing in USD export #128897

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Michael B Johnson wants to merge 6 commits from wave/blender_wave_Apple:liz/fix_instancing into main
pull from: wave/blender_wave_Apple:liz/fix_instancing
merge into: blender:main

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Conversation 9 Commits 6 Files Changed 4 +38 -59
Michael B Johnson commented 2024-10-11 18:29:39 +02:00
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this PR addresses the issues raised in

#126470

Authored by Apple: Zili Zhou

Here are two USD files; one with instancing off and one with it on.

this PR addresses the issues raised in https://projects.blender.org/blender/blender/issues/126470 Authored by Apple: Zili Zhou Here are two USD files; one with instancing off and one with it on.
instance_testOutInstancingOn.usda
187 KiB
instance_testOutInstancingOff.usda
2.4 MiB
Michael B Johnson added 2 commits 2024-10-11 18:29:55 +02:00 
Updated PR to take into account Michael Kowalski's suggestions in #126470.
This ensures that the instanced prims do not contain any children (such as materials) but only a reference to the original prototype hierarchy.
Authored by Apple: Zili (Liz) Zhou, Matt McLin
Michael B Johnson requested review from Jesse Yurkovich 2024-10-11 18:30:58 +02:00
Michael B Johnson requested review from Michael Kowalski 2024-10-11 18:30:59 +02:00
Michael B Johnson added the
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Matt McLin added this to the USD project 2024-10-11 19:00:54 +02:00
Michael B Johnson commented 2024-10-11 19:38:28 +02:00
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We believe this PR fixes the issue without having to do step 1 in the design doc, which is also used by the Alembic exporter.
Therefore, our PR is USD specific and addresses the incorrect scene instancing in the current implementation.

We believe this PR fixes the issue without having to do step 1 in the design doc, which is also used by the Alembic exporter. Therefore, our PR is USD specific and addresses the incorrect scene instancing in the current implementation.
Michael B Johnson added 1 commit 2024-10-11 20:10:37 +02:00
Michael B Johnson changed title from liz/fix_instancing to WIP: fix instancing in USD export 2024-10-11 21:19:53 +02:00
Michael B Johnson added 1 commit 2024-10-12 00:37:34 +02:00
Michael B Johnson added 1 commit 2024-10-14 03:48:48 +02:00
Michael B Johnson added 1 commit 2024-10-14 03:51:16 +02:00
Michael B Johnson changed title from WIP: fix instancing in USD export to fix instancing in USD export 2024-10-14 03:51:23 +02:00
Jesse Yurkovich commented 2024-10-14 18:25:30 +02:00
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It would be good if some notes and discussion on this approach can be made over on the design task - notably about any pros/cons of not doing "step 1" as mentioned. Additionally the description to this PR could use some details about what's been done.

While testing, I've tried to use this with the example file provided at #126470 with the 2 instances in that file rotated (to give them transforms). When I Export with this PR in place, it seems like USD doesn't quite like what's being asked of it - a few Warnings that look like the following are printed:
Warning (secondary thread): in _ReportErrors at line 3172 of C:\db\build\S\VS1564R\build\usd\src\external_usd\pxr\usd\usd\stage.cpp -- In </root/Plane_001/Plane_0/Plane>: Unresolved reference prim path @t:/instanced_collection.usda@</root/Plane> introduced by @t:/instanced_collection.usda@</root/Plane_001/Plane_0/Plane> (recomposing stage on stage @t:/instanced_collection.usda@ <000001C38964ADD0>)

I think I have a few other questions that I'll mention in the design task too that we should get cleared up.

It would be good if some notes and discussion on this approach can be made over on the design task - notably about any pros/cons of not doing "step 1" as mentioned. Additionally the description to this PR could use some details about what's been done. While testing, I've tried to use this with the example file provided at #126470 with the 2 instances in that file rotated (to give them transforms). When I Export with this PR in place, it seems like USD doesn't quite like what's being asked of it - a few Warnings that look like the following are printed: `Warning (secondary thread): in _ReportErrors at line 3172 of C:\db\build\S\VS1564R\build\usd\src\external_usd\pxr\usd\usd\stage.cpp -- In </root/Plane_001/Plane_0/Plane>: Unresolved reference prim path @t:/instanced_collection.usda@</root/Plane> introduced by @t:/instanced_collection.usda@</root/Plane_001/Plane_0/Plane> (recomposing stage on stage @t:/instanced_collection.usda@ <000001C38964ADD0>)` I think I have a few other questions that I'll mention in the design task too that we should get cleared up.
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Michael Kowalski commented 2024-10-14 19:23:03 +02:00
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I will review this today as well.

I will review this today as well.
Michael Kowalski requested changes 2024-10-15 01:20:07 +02:00
Michael Kowalski left a comment
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First of all, thank you so much for tackling this! Nice work!

I made a couple of comments and will continue my review tomorrow.

First of all, thank you so much for tackling this! Nice work! I made a couple of comments and will continue my review tomorrow.
source/blender/io/usd/intern/usd_writer_abstract.cc
@ -249,43 +249,6 @@ void USDAbstractWriter::write_visibility(const HierarchyContext &context,
usd_value_writer_.SetAttribute(attr_visibility, pxr::VtValue(visibility), timecode);
}
bool USDAbstractWriter::mark_as_instance(const HierarchyContext &context, const pxr::UsdPrim &prim)
Michael Kowalski commented 2024-10-15 01:05:49 +02:00
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It looks like you replaced this function with a comparable block of code in usd_writer_transform::do_write() but I wonder if this is necessary. For one thing, the new code introduces an error (see my comment below) but also the original function performs additional error checking. I think the original function needs one change to set the instanceable flag to fix the underlying issue, as I note below.

But please let me know if I'm missing something and there is a reason for replacing this function entirely.

It looks like you replaced this function with a comparable block of code in `usd_writer_transform::do_write()` but I wonder if this is necessary. For one thing, the new code introduces an error (see my comment below) but also the original function performs additional error checking. I think the original function needs one change to set the instanceable flag to fix the underlying issue, as I note below. But please let me know if I'm missing something and there is a reason for replacing this function entirely.
makowalski marked this conversation as resolved
source/blender/io/usd/intern/usd_writer_transform.cc
@ -110,0 +110,4 @@
/* If the xform hierarchy is being instanced, then we want to create a new
* xform prim that will reference the prototype's xform. */
if (usd_export_context_.export_params.use_instancing && context.is_instance()) {
Michael Kowalski commented 2024-10-15 01:10:15 +02:00
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If you restore USDAbstractWriter::mark_as_instance() function (modified to set the instanceable flag on the prim) you could replace this if clause with the following (though I haven't tested this):

if (usd_export_context_.export_params.use_instancing && context.is_instance()) {
    mark_as_instance(context, xform.GetPrim());
 }

This would also fix an error I indicated below.

If you restore `USDAbstractWriter::mark_as_instance()` function (modified to set the instanceable flag on the prim) you could replace this `if` clause with the following (though I haven't tested this): ``` if (usd_export_context_.export_params.use_instancing && context.is_instance()) { mark_as_instance(context, xform.GetPrim()); } ``` This would also fix an error I indicated below.
makowalski marked this conversation as resolved
source/blender/io/usd/intern/usd_writer_transform.cc
@ -110,0 +120,4 @@
pxr::SdfPath inst_path(inst_path_str);
/* To avoid USD errors, make sure the referenced path exists. */
auto new_prim = usd_export_context_.stage->DefinePrim(inst_path);
Michael Kowalski commented 2024-10-15 01:14:35 +02:00
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Actually, we want to define the ref_path prim being referenced below, like this:

usd_export_context_.stage->DefinePrim(ref_path);

Not doing this causes the Unresolved reference prim path USD errors noted by @deadpin.

But. again, I would simply call the original USDAbstractWriter::mark_as_instance() instead.

Actually, we want to define the `ref_path` prim being referenced below, like this: ``` usd_export_context_.stage->DefinePrim(ref_path); ``` Not doing this causes the `Unresolved reference prim path` USD errors noted by @deadpin. But. again, I would simply call the original `USDAbstractWriter::mark_as_instance()` instead.
makowalski marked this conversation as resolved
Michael Kowalski commented 2024-10-15 01:21:58 +02:00
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While testing, I've tried to use this with the example file provided at #126470 with the 2 instances in that file rotated (to give them transforms). When I Export with this PR in place, it seems like USD doesn't quite like what's being asked of it - a few Warnings that look like the following are printed:
Warning (secondary thread): in _ReportErrors at line 3172 of C:\db\build\S\VS1564R\build\usd\src\external_usd\pxr\usd\usd\stage.cpp -- In </root/Plane_001/Plane_0/Plane>: Unresolved reference prim path @t:/instanced_collection.usda@</root/Plane> introduced by @t:/instanced_collection.usda@</root/Plane_001/Plane_0/Plane> (recomposing stage on stage @t:/instanced_collection.usda@ <000001C38964ADD0>)

I noted the cause of this error in my review comments.

EDIT: see my additional comment below.

> While testing, I've tried to use this with the example file provided at #126470 with the 2 instances in that file rotated (to give them transforms). When I Export with this PR in place, it seems like USD doesn't quite like what's being asked of it - a few Warnings that look like the following are printed: > `Warning (secondary thread): in _ReportErrors at line 3172 of C:\db\build\S\VS1564R\build\usd\src\external_usd\pxr\usd\usd\stage.cpp -- In </root/Plane_001/Plane_0/Plane>: Unresolved reference prim path @t:/instanced_collection.usda@</root/Plane> introduced by @t:/instanced_collection.usda@</root/Plane_001/Plane_0/Plane> (recomposing stage on stage @t:/instanced_collection.usda@ <000001C38964ADD0>)` I noted the cause of this error in my review comments. EDIT: see my additional comment below.
Michael Kowalski reviewed 2024-10-15 01:27:38 +02:00
source/blender/io/usd/intern/usd_writer_abstract.cc
@ -282,4 +252,0 @@
context.original_export_path.c_str());
return false;
}
Michael Kowalski commented 2024-10-15 01:27:38 +02:00
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You would need to add this line

 prim.SetInstanceable(true);

To fix the instancing issue.

You would need to add this line ``` prim.SetInstanceable(true); ``` To fix the instancing issue.
makowalski marked this conversation as resolved
Michael Kowalski commented 2024-10-15 17:54:15 +02:00
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I deleted my last comment regarding the scene hierarchy, as I believe this was a local issue for me.

I deleted my last comment regarding the scene hierarchy, as I believe this was a local issue for me.
Michael Kowalski commented 2024-10-15 18:18:29 +02:00
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Okay, I think I was misunderstanding what you were doing. My comments were based on the design I originally had in mind, and you are doing something different. My apologies. Let me close my current comments to avoid confusion and start fresh.

So, the fix to the error noted by @deadpin is to add the following line to the new logic in usd_writer_transform.cc:

usd_export_context_.stage->DefinePrim(ref_path);
Okay, I think I was misunderstanding what you were doing. My comments were based on the design I originally had in mind, and you are doing something different. My apologies. Let me close my current comments to avoid confusion and start fresh. So, the fix to the error noted by @deadpin is to *add* the following line to the new logic in `usd_writer_transform.cc`: ``` usd_export_context_.stage->DefinePrim(ref_path); ```
Michael Kowalski commented 2024-10-15 18:34:56 +02:00
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I think there may be issues when exporting parented meshes. For example, if you export the attached mesh_hierarchy_instance.blend with instancing enabled to USDA, it looks like /root/proto/Plane_0 references /root/Plane and /root/proto/Plane_0/ references /root/Plane/Plane_001 so that I believe /root/Plane/Plane_001 effectively gets instanced twice.

But I could be wrong. Please let me know if I'm misunderstanding.

I think there may be issues when exporting parented meshes. For example, if you export the attached `mesh_hierarchy_instance.blend` with instancing enabled to USDA, it looks like `/root/proto/Plane_0` references `/root/Plane` and `/root/proto/Plane_0/` references `/root/Plane/Plane_001` so that I believe `/root/Plane/Plane_001` effectively gets instanced twice. But I could be wrong. Please let me know if I'm misunderstanding.
mesh_hierarchy_instance.blend
497 KiB
Matt McLin commented 2024-10-16 17:30:12 +02:00
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Thanks Michael and Jesse for the reviews, and for the repro scene for the parenting issue. Yes, we will fix that, and will follow up the discussion in the design task.

Thanks Michael and Jesse for the reviews, and for the repro scene for the parenting issue. Yes, we will fix that, and will follow up the discussion in the design task.
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Zili Zhou (Liz) commented 2024-12-05 00:13:59 +01:00
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Thanks @makowalski @deadpin for the review. We have a fix for the issue Jess mentioned in #128897 (comment), and will push after an internal review.

I'd like to discuss about Michael's comment #128897 (comment). For the example mentioned, both Blender LTS and this PR branch fail to correctly instance the hierarchy. I think this is because Blender USD exporter cannot recognize Collection, since it is not a blender object. In the example attached to the comment mesh_hierarchy_instance.blend, the prototype also collection proto is not added to the hierarchy in the exported USD file.

My proposed solution is:
Add Collection to the object type for letting blender USD exporter know it's a Collection and add it as a Xform --- add OB_COLLECTION = 31 to ObjectType in DNA_object_types.h . Change other places like AbstractHierarchyWriter accordingly.

This solution requires some lower-level changes, so I wanted to consult with everyone first. I’ve attached the proposed USD file for reference. In the USD file, the collection proto is a Xform, so its instancer proto_001 can easily instance the whole hierarchy by using prepend references = </root/proto> without needing to know the details about its children.

Adding Collection as an object type can benefit the following point instancing fix too.

Loop @mont29 in for further discussion.

Thanks @makowalski @deadpin for the review. We have a fix for the issue Jess mentioned in https://projects.blender.org/blender/blender/pulls/128897#issuecomment-1318187, and will push after an internal review. I'd like to discuss about Michael's comment https://projects.blender.org/blender/blender/pulls/128897#issuecomment-1319324. For the example mentioned, both Blender LTS and this PR branch fail to correctly instance the hierarchy. I think this is because Blender USD exporter cannot recognize `Collection`, since it is not a blender object. In the example attached to the comment `mesh_hierarchy_instance.blend`, the prototype also collection `proto` is not added to the hierarchy in the exported USD file. My proposed solution is: _Add `Collection` to the object type for letting blender USD exporter know it's a `Collection` and add it as a `Xform` --- add `OB_COLLECTION = 31` to `ObjectType` in `DNA_object_types.h` . Change other places like `AbstractHierarchyWriter` accordingly._ This solution requires some lower-level changes, so I wanted to consult with everyone first. I’ve attached the proposed USD file for reference. In the USD file, the collection `proto` is a `Xform`, so its instancer `proto_001` can easily instance the whole hierarchy by using `prepend references = </root/proto>` without needing to know the details about its children. Adding `Collection` as an object type can benefit the following point instancing fix too. Loop @mont29 in for further discussion.
mesh_hierarchy_instance_proposed.usda
3.1 KiB
Matt McLin requested review from Bastien Montagne 2024-12-05 00:35:30 +01:00
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