If you open a mesh asset and generate LODs without saving it first, the bounding box is calculated using all available LODs. For example, if LOD1 is larger than LOD0, the resulting bounds will encompass LOD1.
Once the asset is saved, the bounding box calculation changes. From this point on, only LOD0 is considered when computing the bounding box. This means that even if other LODs are larger, the bounding box will tightly fit LOD0 only.
Steps to Reproduce
- Open any static mesh asset
- Enable BBox visualization and Generate LODs
- Notice how all LODs affect BBox size
- Save mesh
- Change reduction setting and regenerate LODs again
- Notice how only LOD0 is taken into consideration for BBox calculation
Hi,
Unfortunately I am unable to reproduce this.
Would you be able to share a small example reproduction project with this please?
Here’s what I’ve done in case I missed anything:
1.) In a blank project, duplicated Cube from Basic shapes and moved it into content.
2.) Opened it, enabled “Bounds” flag in the viewport to display the bounds of the static mesh.
3.) Observed it had LODs generated.
4.) Modified Percent triangle in reduction settings of LOD 1 and hit apply.
This was done on UE 5.6.1.
That being said, an example repro project would be easier to ensure we are seeing the same thing. Thank you!
Regards
Hi,
Your repro steps look good but seems like there some something different when you do duplicate/move.
Also, I don’t think ‘cube’ mesh is complex enough to make problem visible.
Here are exact repro steps with Sphere from Basic shapes:
1.) In a blank project, duplicate Sphere from Basic shapes and move it into content
2.) Open it and set max number of LODs to 2 and press apply changes
[Image Removed] Restart Unreal editor (seems like duplicate or move command does something with mesh so it’s not reproduceable in current instance of unreal editor)
4.) Open Sphere mesh again, change perspective view to ‘left view’ and enable bounds. It should look like this:
[Image Removed] Select LOD1. In LOD reduction settings, set triangle percentage to 100% and press apply
6.) Set triangle percentage back to 0% and press apply
7.) Observe how bbox size is changing and LOD1 is never outside of bbox:
LOD0
[Image Removed] 7b - Optional) You can switch triangle percentage back to 100% then back to 0% how many times you want, bounding box will behave the same
8.) Save mesh
9.) Repeat steps with adjusting triangle percentage 100%-0% and notice how bounding box will stay always the same, and LOD1 will be bigger than bounds.
0% Triangle AFTER SAVE
[Image Removed]
Hope this helps!
Thank you for the detailed steps, I was able to repro this!
I created a bug report for this issue that can be tracked here if/when it’s approved for public visibility: Unreal Engine Issues and Bug Tracker (UE\-350304\).
There is no ETA as priorities for bugs and features can shift at any time.
As a workaround, while it is being looked at, it does look like fully restarting the editor does reset the behavior until saved again.
Thank you again!