Hi Mike,

> I got now the shape that I need, but cannot bevel the outer edges
> and inner extrude the window-frames.

Which edges are you trying to bevel? All of them? Some of the juncture areas where you've got small edges from some slivery pieces will probably be difficult for the fillet engine to handle very well - it won't be able to fillet things if an entire edge or face would be consumed away by the bevel and you probably have several little edges where that would be the case unless you used a very small fillet radius. Also many of the junctures topology like with 7 or 8 edges all coming to a single point with all different angles between the different faces is a quite complex case to fillet, it makes for a difficult to form juncture patch where the fillets are coming together. In sharp edges things like that, the fillet surfaces will be of different widths and are hard to connect up.

Basically when you do a fillet it generates an arc of the particular radius you are asking for in between the surfaces. When the surfaces meet at a small angle it's a short arc that goes between them. When they meet at a big angle, an arc of the same radius is longer so the fillet is longer as well. MoI's fillet engine is not very good at dealing with the complex corner juncture cases that are formed by this kind of situation. You may have better luck in something like SolidWorks or ViaCAD for doing the fillets here.

For extrusion, you can extrude a face that is non-planar, but you may have to use the "Set dir" option on something like that to set the specific extrusion direction direction that you want to use. But extrusion in MoI means to take a curve or a face and produce a solid from it by moving it in one single direction. Maybe you mean something else which in MoI is called "offset" which is taking an outline and making a new shape that is a constant distance away from it?

If you want to offset the window frame edges, you would probably want to do that by duplicating the edges you have as regular curves (select them and do Ctrl+C / Ctrl+V), then take those curves and make them planar in the Top view, by grabbing the corner of the edit frame and using "flat snap" as shown here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=3378.4

You will then be able to offset that planar curve to make a sort of border thickeness shape, like this:






I'm not sure if I understand correctly what it is that you're trying to do with the windows though, if that's not it maybe you could explain it in a bit more detail.

- Michael