Hello Lucy,
Other programs are ideal: Maxon Form etc. But you definitely can do this in Archicad.
The best way would be if you can export your file in Studio format or other 3d format and import directly to AC. If not, then a mesh is your answer:
1) Get as much information as you can from the model. I would want a section of each roof rib in the design, 50 sections more or less.
2) Import a plan view and the sections. If no export function is available, then do it just as you did to post your roof pictures, AC can use jpg's.
3) From the plan view create a mesh. Use the sections you imported to create accurate mesh ridges for each portion of the roof.
4) then convert mesh to roof (see AC help for this). A roof has thickness, whereas a mesh does not.
5) If you are new to AC this might be a bit much. You are going to modify the ridge elevation of 50 x 6 = 300 points at a minimum, the more points you create the smoother the resulting mesh. (I assume 50 ridges broken into a least 6 segments each).
Happy meshing,
-Mark
PS I don't know how to post pictures, I actually started on your roof just to make sure this method works. and it does.
roof design!
