Some years ago I tried to slice a roof object to see what it would do. It went crazy! and I abandoned the crumpled mess to it's doom. But this clever little tool was just doing it's job. It was obeying the rules set for it.
Try this - Draw a line thru a roof object, TRIM one side and then edit the cut edge. (To do this, For 1 or more edges select the roof object and right click. Select 'edit edges/faces'. For all the edges at once, click on the roof and then on the properties pallete click on the edges/faces).
The Height is reset down to 0 and the slope is set to 90 (of course). That's gonna mess up the equations!
Reset those edges as per the rest of your roof, give it a height and set the pitch back to the main roof and voila. It's sanity has returned.
But all you did was shorten it. Not much gain there. Now the real trick.
Draw your line across a corner. ah........ TRIM the roof object. Now you have an extra edge and an extra vertex to play with. Wow. All of a sudden the roof object is editible. The perceptive among you will realise the potential this gives this object. No more recreating that complex roof arrangement or exploding to slabs just because you can't bare to do all that again.
Why didn't anyone share this? I guess the ruling paradigm is to convert to slabs so most have not really explored the roof object's potential. I should point out that the roof object will not give you areas or quantities without some clever programming. The way our industry here is set up we don't need it.
Now my call, in the spirit of opensource, is for you to post your complex roof solutions (just the roof object itself) append to my post and the community can benefit.
I also want to tell you about http://www.archidigm.com/ and also look at the advanced roof tool from http://www.visionrez.com/ so come back.
I have 'just a little' obsessive personality and I drive around looking at buildings to judge how I can built it using ACA objects. Lately it's been roof's and here in Perth Australia, there are only a small percentage of roof shapes that cannot be done with the roof object. Ok in the US, you do build complex roofs and the visionrez tool has been built with you in mind. But for the rest of us the old roof tool may just have some more milage to offer.
If you trim a Roof Object that has it's elevation other than 0 (say for the 2nd Floor), you will find once trimmed that it's elevation is set back to 0 . Simply Select the roof and set the elevation back to it's intended height in the properties pallete ( I use the relevant Floor hieght).
So remember : Cutting corners is now the recommended method of editing your roof object. (You heard it here first :-)
Best to ya (Click here to view all the roof tips).
ps. I am now going to have to rewrite sections of my roof posts now! You can edit!