if surface normals of a dn6/brix map are zero in some places, is there a specific reason it would look OK as a solid mesh in coot in ccp4 format? i used some USF programs to write out a ccp4 map that looks like a nice closed tube in coot. its dn6 or brix counterparts (which i admit are not for coot), however, have surface normals equal to zero at the end of the tube, making it look like the end of an open pipe.
not sure where to start on this - any pointers appreciated, -bryan (with thanks to T.Fenn)
