I found a fix. The 3D view is now perfectly smooth if I start the desktop app with this ENV variable:
```
JAVA_TOOL_OPTIONS="-Dcom.eteks.sweethome3d.j3d.useOffScreen3DView=true"
```

I had the same issue with Sway on recent Intel hardware. 3d acceleration is perfectly smooth using the online version of SweetHome3d in Chrome and Firefox, but the desktop version is rendering at 1 fps or less.