difference(){
    cube(100);
    cube(100,true);   
}

As a side note in a previous thread, I said: > Strangely, the first time that I previewed this model, the > intersection ... didn't.  It showed the original docks and the cubes > for the intersection, and the intersection acted like a union.  > Subsequent previews, including after restarting, got it right.  (Give > or take the convexity issue.)  This is on 2021.01 on Windows. I think I found the culprit for this strange behavior - pilot error, not understanding the behavior of View/Thrown Together. I have a trivial case now: difference(){ cube(100); cube(100,true); } F5s as this: But then I realized that I'd been using View/Thrown Together to look at a polyhedron, and indeed when I switched to View/Preview I got the expected result: There's a similar behavior for intersection: vs This is consistent with the behavior I was experiencing:  I'd load up a model, it would display wrong, I'd mess with it and eventually F6 it (which resets View/Thrown Together), and since I wasn't aware of the View/Thrown Together tie-in it would stay fixed until the next time I happened to look at a model with an intersection or difference while I had View/Thrown Together set. The documentation <https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/First_Steps/Model_views#The_Thrown_Together_View> for View/Thrown Together describes this behavior for difference(), but not for intersection().