Poor performance for "Remove duplicate vertices" for some models #82544

New Issue

Gary Oberbrunner · 2020-11-09T18:03:35+01:00

Gary Oberbrunner commented

2020-11-09 18:03:35 +01:00

System Information
Operating system: Windows 10 (but happens on Linux too)
Graphics card: NVIDIA GeForce GTX 970 (but happens w/ no gfx card too)

Blender Version
Broken: 2.91.0 Beta of 2020-10-26 17:29, hash edf4378c44 (master)
Worked: unknown

Short description of error
"Merge vertices" becomes very slow if glTF object is imported with vertices already merged

Exact steps for others to reproduce the error

Start blender, remove all default objects
Import the attached glTF with:
- Merge Vertices: Turned on
- Shading: Smooth Shading
Select Model Group > Mesh Group > Mesh_0
Enter Edit mode
right-click Merge Vertices > By Distance
repeat the above process, but leave Merge Vertices turned off during import
or

Open attached .blend file
Go to edit mode on the object named Mesh_0_slow
right-click Merge Vertices > By Distance
Try the same with the object named Mesh_0_fast

Note the first time taken: for me it's around 30 sec, which is quite slow
Note the second time taken for Merge Vertices > By Distance is only a second or so

I speculate that this could be because this particular glTF object is reusing some buffers (the 60 meshes are just transformed copies of Mesh_0), so the merge may be doing more work than necessary, but I haven't dug into it.

In my application, I'm looping over all meshes in the scene and removing duplicate verts, so in my case I'm spending the 30 sec per mesh 60 times for a total of 30 min of processing time! Of course I shouldn't need to do that with Merge Vertices turned on, but I have other imported objects and it's all scripted so it's hard to know which ones to merge vs. not.

merge_by_distance_bug.blend
test-molecule-1.glb

**System Information** Operating system: Windows 10 (but happens on Linux too) Graphics card: NVIDIA GeForce GTX 970 (but happens w/ no gfx card too) **Blender Version** Broken: 2.91.0 Beta of 2020-10-26 17:29, hash edf4378c442a (master) Worked: unknown **Short description of error** "Merge vertices" becomes very slow if glTF object is imported with vertices already merged **Exact steps for others to reproduce the error** * Start blender, remove all default objects * Import the attached glTF with: * Merge Vertices: Turned on * Shading: `Smooth Shading` * Select Model Group > Mesh Group > Mesh_0 * Enter Edit mode * right-click Merge Vertices > By Distance * repeat the above process, but leave Merge Vertices turned off during import or - Open attached .blend file - Go to edit mode on the object named `Mesh_0_slow` - right-click Merge Vertices > By Distance - Try the same with the object named `Mesh_0_fast` Note the first time taken: for me it's around 30 sec, which is quite slow Note the second time taken for `Merge Vertices > By Distance` is only a second or so I speculate that this could be because this particular glTF object is reusing some buffers (the 60 meshes are just transformed copies of Mesh_0), so the merge may be doing more work than necessary, but I haven't dug into it. In my application, I'm looping over all meshes in the scene and removing duplicate verts, so in my case I'm spending the 30 sec per mesh 60 times for a total of 30 min of processing time! Of course I shouldn't need to do that with Merge Vertices turned on, but I have other imported objects and it's all scripted so it's hard to know which ones to merge vs. not. [merge_by_distance_bug.blend](https://archive.blender.org/developer/F9253358/merge_by_distance_bug.blend) [test-molecule-1.glb](https://archive.blender.org/developer/F9246885/test-molecule-1.glb)

Gary Oberbrunner commented

2020-11-09 18:03:35 +01:00

Added subscriber: @garyo

Gary Oberbrunner commented

2020-11-09 18:06:10 +01:00

Here's the glTF file: test-molecule-1.glb

Here's the glTF file: [test-molecule-1.glb](https://archive.blender.org/developer/F9246885/test-molecule-1.glb)

Germano Cavalcante commented

2020-11-10 17:12:35 +01:00

Added subscriber: @mano-wii

Germano Cavalcante commented

2020-11-10 17:12:36 +01:00

I can confirm the problem.
I created a simplified file.
The objects are topologically identical, but while 1 takes a long time to merge the vertices, the other is very fast.
merge_by_distance_bug.blend

I can confirm the problem. I created a simplified file. The objects are topologically identical, but while 1 takes a long time to merge the vertices, the other is very fast. [merge_by_distance_bug.blend](https://archive.blender.org/developer/F9253358/merge_by_distance_bug.blend)

Germano Cavalcante commented

2020-11-10 17:19:19 +01:00

Changed status from 'Needs Triage' to: 'Confirmed'

Julien Duroure commented

2020-11-12 15:14:23 +01:00

Added subscriber: @JulienDuroure

Campbell Barton commented

2020-11-18 10:27:54 +01:00

Added subscriber: @ideasman42

Campbell Barton commented

2020-11-18 10:27:54 +01:00

It seems this is an issue with kd-tree balancing. Marking this as a known issue since it doesn't seem like an error in the code.

Campbell Barton changed title from ~~"Remove duplicate vertices" becomes very slow if glTF object is imported with vertices already merged~~ to Poor performance for "Remove duplicate vertices" for some models

2020-11-18 10:30:25 +01:00

Philipp Oeser removed the

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Poor performance for "Remove duplicate vertices" for some models #82544