The lightmaps break when Plane GameObjects cast shadows on them

Unity: Lighting

As Designed

6.5.X

6.4.X

6.3.X

6.0.X

Thank you for reporting a bug to Unity. After reviewing the behavior, we've confirmed it aligns with the current design and intended use of the feature. We understand this may differ from your expectations or workflow. We will close this case as 'As Designed.' If you have feedback on how the feature could better meet your needs, please let us know - we value your input and consider it in future improvements. To solve the issue, please use a material with double sided GI for the plane. The issue you are seeing is because of back facing geometry. Have a look at the validity view mode it is likely red in the areas Unity - Manual: https://docs.unity3d.com/2019.1/Documentation//Manual/GIVis.html

Reproduction steps:
1. Open the attached “IN-125166” project
2. Open the SampleScene
3. Open the “Lighting” window and Generate Lighting
4. Move around the Scene and observe the baked lightmaps

Actual result: The shadows under Plane GameObjects are broken
Expected result: The shadows under Plane GameObjects are normal, same as under the Cube GameObject

Reproducible with: 2022.3.70f1, 6000.0.64f1, 6000.3.3f1, 6000.4.0b3, 6000.5.0a4

Reproducible on: macOS 26.2
Not reproducible on: No other environments tested

The lightmaps break when Plane GameObjects cast shadows on them

Unity: Lighting

As Designed

Prioritise and Follow this issue

Have a workaround or additional info about this issue?

The lightmaps break when Plane GameObjects cast shadows on them

Unity: Lighting

Statuses

As Designed

Resolution Notes

Description

Prioritise and Follow this issue

Have a workaround or additional info about this issue?