Important is that Sketchup can draw on crved surfaces and flat but when flat surfaces
come in via 3ds they are triangulated. So the first thing to do is erase the lines that
divide the flat surfaces (not curved ones) before you start to soften.
You can then use all tools that can be used in Sketchup to build upon these planes.
You can even colour every plane














Those models can be pretty detailed and large...






Peter