Sweet Home 3D can run headless if you set the Java property [font=courier new]java.awt.headless[/font] to [font=courier new]true[/font] (which is probably the default value in Tomcat) and set the Java property [font=courier new]j3d.rend[/font] to [font=courier new]noop[/font].
You may even need no library in that case but I’m not sure.