Actually,calling “show” on the “environ” didn’t work as it’s not the “Plane” itself, but a parent of the Plane. However calling “show” on the Plane resulted in a trianglemesh drawn(with edges, without shading). However, I found another useful thread
here. It says, that you should set the objects attribute in Blender to “Polyset keep descend”, where the keep means, that it should be drawn as well.