Summary
When using Hierarchical Static Meshes (HISM) with Negative Scale Transformations, the static mesh renders with Inverted Normals on hardware which runs ES3.1 and SM5 (first noticed whilst testing on Nintendo Switch 2).
Please select what you are reporting on:
Unreal Editor for Fortnite
What Type of Bug are you experiencing?
Assets
Steps to Reproduce
- Drag out multiple copies of an asset.
- Flip at least one of the scale values to be negative.
- Select all the assets and use Modelling Mode to Harvest Instances.
(I set it to use HISMs, the case may be the same for ISM as well) - Test on a piece of hardware using ES3.1 or SM5.
(I used an Xbox One X, Nintendo Switch and Nintendo Switch 2)
Expected Result
The normals should look correct and be unaffected by negative scaling.
Observed Result
The normals are inverted, showing the interior faces of any asset with negative scale.
Platform(s)
Affected: Mobile*, Nintendo Switch, Nintendo Switch 2, Xbox One, PS4*
Unaffected: PS5, Xbox Series S | X*, High-end PC
*Not tested, but suspected
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Additional Notes
I tested across multiple platforms, in live edit sessions, as well in a private island code. This problem never occurred on my PC.