Converting 2D elements for use in 3D. Any 3D element(s) can be saved as an object with the Save Project As... menu command. (In Archicad 11, Save 3D Model As...) This technique is known as 'slabifying' since such models are often built from slabs. Objects saved in this way are dumb (not parametric), but it's still a useful trick. 2D
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In the site plan, the top view of the house is a separate drawing. Why? The site plan is generated from the first floor. The roofs are only seen in their entirety on the roof story. The only way to get the roofs on the first floor is to draw (trace, copy/paste, whatever) them. We don't like drawing things.
The roof plan has to be drawn. Sigh. Update: I changed the recommended line weights, making them lighter. I think this will make the structure plan read better.
Which you need to do from time to time, for several purposes.
The only difference between a perspective and an axon is in the 3D projection settings. And you usually do more than one axon, so you'll probably want to know about that.