I'm creating a polygon using BRepBuilderAPI_MakePolygon, then using BRepPrimAPI_MakePrism to extrude the polygon to become a 3D shape.
However, the resulting shape isn't being closed.
E.g. if I create the polygon using coordinates in the X-Y plane, then extrude in the Z direction using BRepPrimAPI_MakePrism with the constructor that takes a gp_Vec(0, 0, 1), it creates a shape with the top being the polygon and has sides, but there's no bottom (which should be the same as the top polygon, with reversed Z normals).
Is this expected behavior?
How do you generate the bottom?