Flipped normals in FBX 3D models when using plugins usually result from mismatched coordinate systems (e.g., left-hand vs right-hand) or differing normal calculation methods between the original 3D software and the plugin.
- Normals determine a face’s front/back; if the plugin interprets the FBX’s coordinate space differently than the model’s source (like Blender to a Unity plugin) or recalculates normals instead of using the saved ones, faces can flip. - Try enabling "preserve normals" in the plugin’s import settings or matching the coordinate system (e.g., Y-up vs Z-up) between your 3D software and the plugin to fix this.