OBJ importer in 3.3 does not keep the vertex order #100421

New Issue

Amy Moo · 2022-08-15T20:42:55+02:00

Amy Moo commented

2022-08-15 20:42:55 +02:00

System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 3060/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 516.40

Blender Version
Broken: version: 3.4.0 Alpha, branch: master, commit date: 2022-08-14 18:40, hash: 659b63751d
Worked: (newest version of Blender that worked as expected)

Short description of error
In order for morph to work in DAZ Studio, the morphed mesh has to have the same number of vertices and faces, and the same order of the vertices. This is the reason I asked for it many years ago, see https:*developer.blender.org/T27145 and https:*developer.blender.org/T36159. Therefore, it is not an issue for the Wavefront (.obj) (legacy) importer or exporter.

Exact steps for others to reproduce the error

Start with cube, subdivide it 10x in edit mode
Export cube as .obj and import it.
Move imported cube next to original
Create basis shape key and another shape key.
Enter edit mode, select all vertices, run checker deselect operator and scale selected vertices a bit, exit edit mode.
Select original cube
Create basis shape key
Add duplicate cube to selection

Use transfer shape key operator to copy shape key from duplicate to original.

Left cube is imported duplicate with desired keyshape, right cube is after step 9.

**System Information** Operating system: Windows-10-10.0.19041-SP0 64 Bits Graphics card: NVIDIA GeForce RTX 3060/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 516.40 **Blender Version** Broken: version: 3.4.0 Alpha, branch: master, commit date: 2022-08-14 18:40, hash: `659b63751d` Worked: (newest version of Blender that worked as expected) **Short description of error** In order for morph to work in DAZ Studio, the morphed mesh has to have the same number of vertices and faces, and the same order of the vertices. This is the reason I asked for it many years ago, see https:*developer.blender.org/T27145 and https:*developer.blender.org/T36159. Therefore, it is not an issue for the Wavefront (.obj) (legacy) importer or exporter. **Exact steps for others to reproduce the error** - Start with cube, subdivide it 10x in edit mode - Export cube as .obj and import it. - Move imported cube next to original - Create basis shape key and another shape key. - Enter edit mode, select all vertices, run checker deselect operator and scale selected vertices a bit, exit edit mode. - Select original cube - Create basis shape key - Add duplicate cube to selection # Use transfer shape key operator to copy shape key from duplicate to original. ![Untitled.png](https://archive.blender.org/developer/F13390898/Untitled.png) Left cube is imported duplicate with desired keyshape, right cube is after step 9.

Amy Moo commented

2022-08-15 20:42:55 +02:00

Added subscriber: @amy_aimei

Amy Moo commented

2022-08-15 20:53:55 +02:00

Additional information:
I have tested the build on Aug 6 (800c7dbf41). It works. Therefore, it must be the changes after that date cause the issue.

Additional information: I have tested the build on Aug 6 (800c7dbf41a2). It works. Therefore, it must be the changes after that date cause the issue.

Aras Pranckevicius commented

2022-08-15 21:19:12 +02:00

Added subscriber: @aras_p

Aras Pranckevicius commented

2022-08-15 21:20:37 +02:00

@amy_aimei Can you attach the sample files? i.e. the obj file you get from step 2 (what's exported from daz), and the obj file you get from step 6 (what's exported out of blender after modifications)

Amy Moo commented

2022-08-15 21:34:00 +02:00

I've made a simple way to check and the issue seems to be located in the importer code. I wrote a Python script in Blender to list the vertices in order with the corresponding coordinate. Then, use the Wavefront (.obj) (legacy) importer with the "Keep Vert Order" option enabled to import the file. Use the script to list the vertices in order with the corresponding coordinate. It is the baseline, i.e., the correct vertices order. Then, export it with Wavefront (.obj). Then, import it back using Wavefront (.obj) (legacy). Use the script to list the vertices. I noticed that it is fine. This means the exporter is fine. But when I used the Wavefront (.obj) to import the obj, then export it by using Wavefront (.obj) (legacy). Then, import it back using Wavefront (.obj) (legacy). Use the script to list the vertices. I noticed the coordinates don't match. This means the vertices order is not being preserved when it is imported. The issue at the importer code.

I guess, the issue is caused by the change https://developer.blender.org/rBd76583cb4a16315c196f07f4acb9340f341bee47

I've made a simple way to check and the issue seems to be located in the importer code. I wrote a Python script in Blender to list the vertices in order with the corresponding coordinate. Then, use the Wavefront (.obj) (legacy) importer with the "Keep Vert Order" option enabled to import the file. Use the script to list the vertices in order with the corresponding coordinate. It is the baseline, i.e., the correct vertices order. Then, export it with Wavefront (.obj). Then, import it back using Wavefront (.obj) (legacy). Use the script to list the vertices. I noticed that it is fine. This means the exporter is fine. But when I used the Wavefront (.obj) to import the obj, then export it by using Wavefront (.obj) (legacy). Then, import it back using Wavefront (.obj) (legacy). Use the script to list the vertices. I noticed the coordinates don't match. This means the vertices order is not being preserved when it is imported. The issue at the importer code. I guess, the issue is caused by the change https://developer.blender.org/rBd76583cb4a16315c196f07f4acb9340f341bee47

Amy Moo commented

2022-08-15 21:43:35 +02:00

The script I used to list the vertices in order with the corresponding coordinate:
(Select the object to check before running the script.)

import bpy

currMode = bpy.context.active_object.mode
bpy.ops.object.mode_set(mode='OBJECT')
targetMesh = bpy.context.active_object.data
targetVerts = targetMesh.vertices
for targetVert in targetVerts:
  print(targetVert.index, targetVert.co)
bpy.ops.object.mode_set(mode=currMode)

The script I used to list the vertices in order with the corresponding coordinate: (Select the object to check before running the script.) ``` import bpy currMode = bpy.context.active_object.mode bpy.ops.object.mode_set(mode='OBJECT') targetMesh = bpy.context.active_object.data targetVerts = targetMesh.vertices for targetVert in targetVerts: print(targetVert.index, targetVert.co) bpy.ops.object.mode_set(mode=currMode) ```

Amy Moo commented

2022-08-15 21:45:35 +02:00

The obj I used to test{F13389325}

The obj I used to test{[F13389325](https://archive.blender.org/developer/F13389325/temp.obj)}

Richard Antalik commented

2022-08-16 05:39:57 +02:00

Added subscriber: @iss

Richard Antalik commented

2022-08-16 05:39:57 +02:00

Can confirm this, and since Blender can do this with shape keys, I will update description to eliminate need for 3rd party software

Richard Antalik commented

2022-08-16 05:59:25 +02:00

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

Aras Pranckevicius self-assigned this 2022-08-16 06:56:51 +02:00

Aras Pranckevicius changed title from ~~OBJ importer/exporter does not keep the vertice order~~ to OBJ importer in 3.3 does not keep the vertex order

2022-08-16 06:57:29 +02:00

blender-admin commented

2022-08-16 12:49:27 +02:00

This issue was referenced by efdcef7855

This issue was referenced by efdcef7855e378bc3183ceab16e17f3dfd8e3c76

Aras Pranckevicius commented

2022-08-16 12:49:52 +02:00

Changed status from 'Confirmed' to: 'Resolved'

Aras Pranckevicius closed this issue

2022-08-16 12:49:52 +02:00

Bastien Montagne added this to the Pipeline, Assets & IO project 2023-02-09 15:40:02 +01:00

Bastien Montagne removed this from the Pipeline, Assets & IO project 2023-02-10 12:49:18 +01:00

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OBJ importer in 3.3 does not keep the vertex order #100421

Use transfer shape key operator to copy shape key from duplicate to original.