Problem in implementation of a TGeo volume with holes

Dear ROOTers,

in attachment you can find a macro which I am implementing to create a TGeo volume which should consist in a thin shape with some holes. The shape has a form not too regular, so I used TGeoXtru to define it, instead of gluing together plenty of boxes and Arb8 shapes. Then, I implemented the holes and I tried to compose the shape with the holes, and to generate a final volume with this kind of "pierced" volume whose shape I created.

As you can see from the example plots, when I draw this object in the GL viewer, I notice that, if I see it from one side, it looks fine. If I look at it from the other side, it looks strange, because some part of the "filled" volume disappears.

Could someone help me in understanding where's the problem?

thanks and best regards

       Alberto

• text/x-c++src attachment: gfoil1.C