New obj exporter: Scale factor is applied incorrectly #96415

New Issue

Yahya Janani · 2022-03-13T22:41:55+01:00

Yahya Janani commented

2022-03-13 22:41:55 +01:00

System Information
Operating system: Windows-10-10.0.19044-SP0 64 Bits
Graphics card: GeForce 840M/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 388.73

Blender Version
Broken: version: 3.1.0, branch: master, commit date: 2022-03-08 18:16, hash: c77597cd0e
Worked: (newest version of Blender that worked as expected)

Short description of error
There is not an error but it's a little problem to exporting object(s) as .obj format from blender to maya.
I tested it on my own lap top and our studio's computers too and got same result at all of them.

In previous versions, the position of all vertices of an imported object was maintained in wherever they were in blender, and only the origin was moved to the (0, 0, 0) which was true.
In the new version, all verts position is shifted along with object's origin

Exact steps for others to reproduce the error

Open .blend file in previous version (say 3.0.0)
Export object in .obj format. In obj export settings , set scale to 10
Open default scene -> delete everything -> Import back the .obj file
Open same .blend file in 3.1 release
Export object in .obj format. In obj export settings , set scale to 10
Open default scene -> delete everything -> Import back the .obj file

3.0.0	3.1.0

Test File:
#96415.blend

**System Information** Operating system: Windows-10-10.0.19044-SP0 64 Bits Graphics card: GeForce 840M/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 388.73 **Blender Version** Broken: version: 3.1.0, branch: master, commit date: 2022-03-08 18:16, hash: `c77597cd0e` Worked: (newest version of Blender that worked as expected) **Short description of error** There is not an error but it's a little problem to exporting object(s) as .obj format from blender to maya. I tested it on my own lap top and our studio's computers too and got same result at all of them. In previous versions, the position of all vertices of an imported object was maintained in wherever they were in blender, and only the origin was moved to the (0, 0, 0) which was true. In the new version, all verts position is shifted along with object's origin **Exact steps for others to reproduce the error** - Open .blend file in previous version (say 3.0.0) - Export object in .obj format. In obj export settings , set scale to 10 - Open default scene -> delete everything -> Import back the .obj file - Open same .blend file in 3.1 release - Export object in .obj format. In obj export settings , set scale to 10 - Open default scene -> delete everything -> Import back the .obj file | 3.0.0 | 3.1.0 | | -- | -- | | ![image.png](https://archive.blender.org/developer/F12926661/image.png) | ![image.png](https://archive.blender.org/developer/F12926663/image.png) | Test File: [#96415.blend](https://archive.blender.org/developer/F12926666/T96415.blend)

Yahya Janani commented

2022-03-13 22:41:55 +01:00

Added subscriber: @yaiiaj

Pratik Borhade commented

2022-03-14 04:32:34 +01:00

Added subscriber: @PratikPB2123

Pratik Borhade commented

2022-03-14 04:32:34 +01:00

Changed status from 'Needs Triage' to: 'Needs User Info'

Pratik Borhade commented

2022-03-14 04:32:34 +01:00

Hi, thanks for the report.
In both the cases object origin has moved to world origin (as shown in the image).
So what exactly the issue is? Or is that the issue itself?

Hi, thanks for the report. In both the cases object origin has moved to world origin (as shown in the image). So what exactly the issue is? Or is that the issue itself?

Yahya Janani commented

2022-03-14 08:55:36 +01:00

Hello dear Pratik and thank you for your answer.
If you look closely at the pictures, I'm not just talking about origin itself but about vertices.
In previous versions, the position of all vertices of an imported object was maintained in wherever they were in blender, and only the origin was moved to the (0, 0, 0) which was true.
In the new version, the movement of all vertices with origin is problematic, not just the origin itself.

Thank you again.

Hello dear Pratik and thank you for your answer. If you look closely at the pictures, I'm not just talking about origin itself but about vertices. In previous versions, the position of all vertices of an imported object was maintained in wherever they were in blender, and only the origin was moved to the (0, 0, 0) which was true. In the new version, the movement of all **vertices with origin** is problematic, not just the origin itself. ![pic h.jpg](https://archive.blender.org/developer/F12926343/pic_h.jpg) ![pic_e.jpg](https://archive.blender.org/developer/F12926351/pic_e.jpg) ![pic_i.jpg](https://archive.blender.org/developer/F12926369/pic_i.jpg) Thank you again.

Scurest commented

2022-03-14 11:48:10 +01:00

Added subscriber: @scurest

Scurest commented

2022-03-14 11:48:10 +01:00

Looks like the Python exporter transforms verts with

  scaling_factor @ axis_conversion @ ob_mat

while the C++ exporter is using

  axis_conversion @ ob_mat @ scaling_factor

The difference is in the latter, the scaling factor does not affect the translation in ob_mat.

Probably swapping these lines will fix it.

Looks like the Python exporter transforms verts with ``` scaling_factor @ axis_conversion @ ob_mat ``` while the C++ exporter is using ``` axis_conversion @ ob_mat @ scaling_factor ``` The difference is in the latter, the scaling factor does not affect the translation in ob_mat. Probably swapping [these lines](https://github.com/blender/blender/blob/8eb189925e028a480d13e43d60216b98b73cfa16/source/blender/io/wavefront_obj/exporter/obj_export_mesh.cc#L242-L243) will fix it.

Pratik Borhade commented

2022-03-14 12:25:08 +01:00

Now I see, thanks for clarifying. I will make some edits in task description before confirming
I've not tested the proposed fix yet but will do in a bit :)

Now I see, thanks for clarifying. I will make some edits in task description before confirming I've not tested the proposed fix yet but will do in a bit :)

Yahya Janani commented

2022-03-14 12:37:23 +01:00

Thank you very much.

Pratik Borhade commented

2022-03-14 12:39:27 +01:00

Changed status from 'Needs User Info' to: 'Confirmed'

Pratik Borhade commented

2022-03-14 13:00:17 +01:00

Added subscriber: @howardt

Pratik Borhade commented

2022-03-14 13:00:17 +01:00

Probably swapping these lines will fix it.

@scurest's suggestion actually works for me.
@howardt , can you take a look?

> Probably swapping [these lines](https://github.com/blender/blender/blob/8eb189925e028a480d13e43d60216b98b73cfa16/source/blender/io/wavefront_obj/exporter/obj_export_mesh.cc#L242-L243) will fix it. @scurest's suggestion actually works for me. @howardt , can you take a look?

Pratik Borhade changed title from ~~obj export problem~~ to New obj exporter: Scale factor is applied incorrectly

2022-03-15 12:43:33 +01:00

Aras Pranckevicius self-assigned this 2022-03-15 12:48:58 +01:00

blender-admin commented

2022-03-19 22:13:21 +01:00

This issue was referenced by 9ed566efb6

This issue was referenced by 9ed566efb67a20c66e6d8c2965546b89bdd9764e

blender-admin commented

2022-03-19 22:13:21 +01:00

This issue was referenced by 5bfdaaa800

This issue was referenced by 5bfdaaa80082be12af9850a2af294823005abb72

Howard Trickey commented

2022-03-19 22:17:27 +01:00

Changed status from 'Confirmed' to: 'Resolved'

Howard Trickey closed this issue

2022-03-19 22:17:27 +01:00

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New obj exporter: Scale factor is applied incorrectly #96415