Mirroring in object mode screws up normals #78512

New Issue

João Kalva · 2020-07-01T21:25:37+02:00

João Kalva commented

2020-07-01 21:25:37 +02:00

System Information
Operating system: Windows 10
Graphics card: RX 480

Blender Version
Broken: 2.83

Short description of error
Mirroring objects in edit mode inverts normals. This does not happen with Mirror modifier and mirroring in edit mode.

Exact steps for others to reproduce the error
Select an object
Ctrl M -> X, Y or Z

1st: Ctrl M (edit mode)
2nd: Ctrl M on instances (object mode)
3rd: Ctrl M on single users (object mode)
4th: Using mirror modifier
5th: Mirroring the object using mirror modifier (without applying, object mode)
6th: Applied mirror and deleted unwanted parts

I did a bunch of tests regarding mirroring.
What I found is that when you mirror objects using the Mirror Modifier and in edit mode, they cause no problems in other software

The problem is when you Ctrl M in object mode.
After doing so, you don't get the indication of inverted normals in Blender's viewport (unlike edit mode).

Nothing seem to fix it. Applying transforms, recalculating normals, triangulization, export settings, etc etc.

This is the same file as in the first screenshot. Face orientation is on, meaning the purples represent normals pointing outwards.

Despite not having any bad indication in Blender, when you import it as fbx and import it to the majority of other software, it displays as flipped normals
Displayed Flipped: Substance Painter, Unreal, Marmoset Toolbag 3

Displayed normally: Unity

**System Information** Operating system: Windows 10 Graphics card: RX 480 **Blender Version** Broken: 2.83 **Short description of error** Mirroring objects in edit mode inverts normals. This does not happen with Mirror modifier and mirroring in edit mode. **Exact steps for others to reproduce the error** Select an object Ctrl M -> X, Y or Z ![06.png](https://archive.blender.org/developer/F8657779/06.png) 1st: Ctrl M (edit mode) 2nd: Ctrl M on instances (object mode) 3rd: Ctrl M on single users (object mode) 4th: Using mirror modifier 5th: Mirroring the object using mirror modifier (without applying, object mode) 6th: Applied mirror and deleted unwanted parts I did a bunch of tests regarding mirroring. What I found is that when you mirror objects using the Mirror Modifier and in edit mode, they cause no problems in other software The problem is when you Ctrl M in object mode. After doing so, you don't get the indication of inverted normals in Blender's viewport (unlike edit mode). Nothing seem to fix it. Applying transforms, recalculating normals, triangulization, export settings, etc etc. ![07.png](https://archive.blender.org/developer/F8657790/07.png) This is the same file as in the first screenshot. Face orientation is on, meaning the purples represent normals pointing outwards. Despite not having any bad indication in Blender, when you import it as fbx and import it to the majority of other software, it displays as flipped normals Displayed Flipped: Substance Painter, Unreal, Marmoset Toolbag 3 ![03.png](https://archive.blender.org/developer/F8657798/03.png) ![04.png](https://archive.blender.org/developer/F8657805/04.png) ![01.png](https://archive.blender.org/developer/F8657808/01.png) Displayed normally: Unity ![05.png](https://archive.blender.org/developer/F8657799/05.png)

blender-admin commented

2020-07-01 21:25:37 +02:00

#92366 was marked as duplicate of this issue

João Kalva commented

2020-07-01 21:25:38 +02:00

Added subscriber: @joaokalva

Richard Antalik commented

2020-07-02 05:22:25 +02:00

Added subscriber: @iss

Richard Antalik commented

2020-07-02 05:22:25 +02:00

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

Richard Antalik commented

2020-07-02 05:22:25 +02:00

The problem is when you Ctrl M in object mode.
After doing so, you don't get the indication of inverted normals in Blender's viewport (unlike edit mode).

I can not reproduce this. Can you provide example file?

You can go to edit mode select all geometry and flip normals as workaround.

>The problem is when you Ctrl M in object mode. >After doing so, you don't get the indication of inverted normals in Blender's viewport (unlike edit mode). I can not reproduce this. Can you provide example file? You can go to edit mode select all geometry and flip normals as workaround.

João Kalva commented

2020-07-02 14:37:19 +02:00

In the Gif I create a new project, add suzanne, activate face orientation.
Mirroring with Ctrl-M in edit mode gives the correct feedback.

Then I add another suzanne, and this time I am mirroring in object mode.
Doing so does not give me the feedback that it has flipped normals.
Mirrored Objects.blend
This is the .blend of the previous tests

![03.gif](https://archive.blender.org/developer/F8659676/03.gif) In the Gif I create a new project, add suzanne, activate face orientation. Mirroring with Ctrl-M in edit mode gives the correct feedback. Then I add another suzanne, and this time I am mirroring in object mode. Doing so does not give me the feedback that it has flipped normals. [Mirrored Objects.blend](https://archive.blender.org/developer/F8659681/Mirrored_Objects.blend) This is the .blend of the previous tests

Diogo Valadares Reis dos Santos commented

2020-07-02 22:56:22 +02:00

Added subscriber: @Diogo_Valadares

Diogo Valadares Reis dos Santos commented

2020-07-02 22:56:22 +02:00

maybe a duplicate https://developer.blender.org/T37652

Richard Antalik commented

2020-07-03 01:41:07 +02:00

Thanks for explanation, I get what the problem is now.

In #78512#971430, @joaokalva wrote:
Then I add another suzanne, and this time I am mirroring in object mode.
Doing so does not give me the feedback that it has flipped normals.

This is correct. Mirroring in object mode will only apply scale of -1 in mirroed axis. Normals are not flipped. During export object scale is applied though. You can do it manually in menu Object > Apply > Scale

This is working as intended and there fore not considered a bug.

I am not familiar with workflows here but please look at one of the community websites: https://www.blender.org/community/
If you think this should be changed, please use other channels: https://wiki.blender.org/wiki/Communication/Contact#User_Feedback_and_Requests

For more information on why this isn't considered a bug, visit: https://wiki.blender.org/wiki/Reference/Not_a_bug

Thanks for explanation, I get what the problem is now. > In #78512#971430, @joaokalva wrote: > Then I add another suzanne, and this time I am mirroring in object mode. > Doing so does not give me the feedback that it has flipped normals. This is correct. Mirroring in object mode will only apply scale of -1 in mirroed axis. Normals are not flipped. During export object scale is applied though. You can do it manually in menu Object > Apply > Scale This is working as intended and there fore not considered a bug. I am not familiar with workflows here but please look at one of the community websites: https://www.blender.org/community/ If you think this should be changed, please use other channels: https://wiki.blender.org/wiki/Communication/Contact#User_Feedback_and_Requests For more information on why this isn't considered a bug, visit: https://wiki.blender.org/wiki/Reference/Not_a_bug

Richard Antalik commented

2020-07-03 01:41:30 +02:00

Closed as duplicate of #37652

Richard Antalik closed this issue

2020-07-03 01:41:30 +02:00

João Kalva commented

2020-07-03 12:14:55 +02:00

Allow me to disagree, but I don't think this is expected behavior.
Applying transformation doesn't fix the issue, and if I don't happen to have a slight technical background, there's no way I can know what is going on because I get no information about the problem.

In my experience, since I have started using Substance Painter 1.5 years ago this was a problem and I'd never understand why until I decided to spend these 6 hours trying to tackle the problem.
This was not exclusive to me.

https://polycount.com/discussion/220942/blender-flipping-normals-when-mirroring-objects/
"It's very annoying, but that is just how that operator works"
"It's a long standing and very annoying feature"
https://www.facebook.com/groups/265386433819253/?post_id=1137569739934247&comment_id=1138373413187213
Other people also reported how annoying it was to work around this and how inconsistent blender was when this problem arrived

My suggestion is not to fix anything, but to simply remove Ctrl M from object mode to avoid confusion that can be very annoying to deal with

Allow me to disagree, but I don't think this is expected behavior. Applying transformation doesn't fix the issue, and if I don't happen to have a slight technical background, there's no way I can know what is going on because I get no information about the problem. In my experience, since I have started using Substance Painter 1.5 years ago this was a problem and I'd never understand why until I decided to spend these 6 hours trying to tackle the problem. This was not exclusive to me. https://polycount.com/discussion/220942/blender-flipping-normals-when-mirroring-objects/ "It's very annoying, but that is just how that operator works" "It's a long standing and very annoying feature" https://www.facebook.com/groups/265386433819253/?post_id=1137569739934247&comment_id=1138373413187213 Other people also reported how annoying it was to work around this and how inconsistent blender was when this problem arrived My suggestion is not to fix anything, but to simply remove Ctrl M from object mode to avoid confusion that can be very annoying to deal with

Richard Antalik commented

2020-07-07 05:55:30 +02:00

In #78512#972225, @joaokalva wrote:
Allow me to disagree, but I don't think this is expected behavior.
Applying transformation doesn't fix the issue, and if I don't happen to have a slight technical background, there's no way I can know what is going on because I get no information about the problem.

In my experience, since I have started using Substance Painter 1.5 years ago this was a problem and I'd never understand why until I decided to spend these 6 hours trying to tackle the problem.
This was not exclusive to me.

https://polycount.com/discussion/220942/blender-flipping-normals-when-mirroring-objects/
"It's very annoying, but that is just how that operator works"
"It's a long standing and very annoying feature"
https://www.facebook.com/groups/265386433819253/?post_id=1137569739934247&comment_id=1138373413187213
Other people also reported how annoying it was to work around this and how inconsistent blender was when this problem arrived

My suggestion is not to fix anything, but to simply remove Ctrl M from object mode to avoid confusion that can be very annoying to deal with

I would agree with you, but my point is that we use this bugtracker strictly to fix unintended functionality of code (bugs). Please use following link to provide feedback or suggestions https://wiki.blender.org/wiki/Communication/Contact#User_Feedback_and_Requests

> In #78512#972225, @joaokalva wrote: > Allow me to disagree, but I don't think this is expected behavior. > Applying transformation doesn't fix the issue, and if I don't happen to have a slight technical background, there's no way I can know what is going on because I get no information about the problem. > > In my experience, since I have started using Substance Painter 1.5 years ago this was a problem and I'd never understand why until I decided to spend these 6 hours trying to tackle the problem. > This was not exclusive to me. > > https://polycount.com/discussion/220942/blender-flipping-normals-when-mirroring-objects/ > "It's very annoying, but that is just how that operator works" > "It's a long standing and very annoying feature" > https://www.facebook.com/groups/265386433819253/?post_id=1137569739934247&comment_id=1138373413187213 > Other people also reported how annoying it was to work around this and how inconsistent blender was when this problem arrived > > My suggestion is not to fix anything, but to simply remove Ctrl M from object mode to avoid confusion that can be very annoying to deal with I would agree with you, but my point is that we use this bugtracker strictly to fix unintended functionality of code (bugs). Please use following link to provide feedback or suggestions https://wiki.blender.org/wiki/Communication/Contact#User_Feedback_and_Requests

Philipp Oeser commented

2021-10-20 15:25:00 +02:00

Added subscribers: @de_bugger, @lichtwerk

Philipp Oeser referenced this issue

2023-09-19 10:22:08 +02:00

Mirroring in Edit and Sculpt Modes Inverts Normals #112550

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