Mirror modifier will modify custom normals along the center where the mirror starts. #109480

New Issue

MVPuccino · 2023-06-29T02:31:34+02:00

MVPuccino commented

2023-06-29 02:31:34 +02:00

System Information
Operating system: ArchLinux (Plasma Wayland)
Graphics card: RX 570 8GB | Mesa 23.1.3-1

Blender Version
Broken: 3.6.0, c7fc78b81e, blender-v3.6-release, 2023-06-27
Worked: Never

The mirror modifier will modify custom normals of vertices found in the center line of the mirror.
This only happens with Merge turned on.
So this especially a pain when trying to use with other modifiers like SubSurf below it.

Steps to reproduce

Auto-Smooth the object. (Suzanne was used in testing, 180° angle was used for comfort.)
Delete one half of the object
Apply mirror.
Enable On Cage, everything should look as expected for now.
Edit any normal in the middle point where the mirror starts (It is recommended to disable On Cage at this point to understand how the custom normals should actually be).
Turn On Cage back on to see that the mirror modifier has modified the custom normal.

Workaround
Apply without Merge enabled, then select all the middle vertices (or just all the vertices for convenience), go to Mesh -> Clean Up -> Merge by Distance.
Although ideally one should be able to keep the mirror modifier on without having to apply it and still have proper custom normals.

**System Information** Operating system: ArchLinux (Plasma Wayland) Graphics card: RX 570 8GB | Mesa 23.1.3-1 **Blender Version** Broken: 3.6.0, c7fc78b81ecb, blender-v3.6-release, 2023-06-27 Worked: Never The mirror modifier will modify custom normals of vertices found in the center line of the mirror. **This only happens with Merge turned on.** So this especially a pain when trying to use with other modifiers like SubSurf below it. **Steps to reproduce** 1. Auto-Smooth the object. (Suzanne was used in testing, 180° angle was used for comfort.) 1. Delete one half of the object 1. Apply mirror. 1. Enable On Cage, everything should look as expected for now. 1. Edit any normal in the middle point where the mirror starts (It is recommended to disable On Cage at this point to understand how the custom normals should actually be). 1. Turn On Cage back on to see that the mirror modifier has modified the custom normal. **Workaround** Apply without Merge enabled, then select all the middle vertices (or just all the vertices for convenience), go to Mesh -> Clean Up -> Merge by Distance. Although ideally one should be able to keep the mirror modifier on without having to apply it and still have proper custom normals.

MessedUpNormals.blend

1.4 MiB

MVPuccino added the

labels 2023-06-29 02:31:34 +02:00

YimingWu commented

2023-06-29 05:15:39 +02:00