MODELLING OF DUCT PASSING THROUGH RISER AT 45 DEGREE.

HI 

I HAVE A DUCT PASSING VIA RISER FROM  L1 TO L6 AT AN ANGLE OF 45 DEGREE OR SAY NOT IN A 90 DEGREE VERTICAL WAY.  PLEASE COULD YOU BE SO KIND TO DEMONSTRATE HOW THIS CAN BE MODELED. 

MANY THANKS