Now it is good (fast) again on my machine. Maybe another Win10 update? I'm not sure.

For additional information I have include that this exact problem first occurred around Mar. 17., I have immediately notified Emmanuel. After a few days and a supposed Win10 update the problem went away. But now it came back. I do not know what type of update messes with this. My problem only ...

hal9000, please install Java, download the Jar executable version of Sweet Home 3D, and run it with the following command in a cmd window:
java -Dcom.eteks.sweethome3d.j3d.version=1.5.2 -jar [i]/path/to/[/i]SweetHome3D-5.4.jar (to get easily the path to [font=courier new]SweetHome3D-5.4.jar[/font ...

I can confirm. Since the last Win10 update, SH3D became very slow. Unusable this way.