The round (2 pitch) roof was based on a 16 side polygon and how they usually construct it anyway though usually 8 sides. The flat top (name?) was created using 2 pitches and then adding a third 0 slope roof as similar to what I describe here. The Pizza hut roof is done using the double slope roof (check the properties pallete) as can the Mansard roof if the pitching is on all 4 sides (not 2 like I've shown).
The Dormer is simply another roof (object) sat above the main roof. The trick here is to create a 5 side roof shape, with the back planted end having 2 (triangular) sides with no overhang and the slope set to 90. UPDATE - see technique for dormer roofs and other holes. The roof object cannot have holes so yes there will be roof in the middle of dormer and won't work for sections thru' here. For a schematic section you could use a masking object or simply edit the section and delete the lines. That may even possibly get you thru' a construction drawing as well.
The floating or planted Gable is again another simple roof object with 5 sides. The trick here is the 2 sides with slope are too small to be seen so it appears to be a triangle. The VisionRez roof can do this slope without a length being required which is very smo
The Gablet or Dutch Gable (Gablet-uk) along with the Mansard, Half Hip and derivatives can be created using the technique describe in part 2. via editing edges.
The Skillion roof is the most simple but not obvious with the roof object. It would appear to be native to a slab. But aecSlabs behave differently (displayReps) and so I will use the RO instead.
Trick is to create a 90 slope roof to start with and only add a slope to the one side edge. It can also turn corners and wrap around a house, even completely around. To get a verandah roof all around a house (with a hole in the middle for the house) create one roof up to the hip and then another to complete. Connecting at the hip end will disguise the use of two objects and there will be no unwanted lines in plan, elevation & model. (UPDATE: If you create a full square roof and add a second pitch at 0 to one edge at a height between the pitch line and ridge, you will get a hole. This is demonstrated in my file posted at AUGI and Adesk NG.
Hopefully you can see that the roof object has some versitility. You may well need to revert to slabs to do a complex roof but the RO can certainly go further than what may be immediately obvious. I seriously believe that with a little tweaking by the Autodesk team, the roof object could be a great tool for residential roof's. As it is - it's almost there! I don't care for edge styles as I am happy using a wall style for that But it does need ;
- Ability to add/remove vertices (critical) UPDATE - it's there but hidden.
- Ability to cut holes (ok not so critical) UPDATE - reasonable workaround.
- Styles (ok not so critical but would be nice)
Next I want to look at when a roof needs to overlap itself and the simple cut out section.