Roof by Extrusion behavior discrepancies.

[patricks]

I have a couple of different barrel-vaulted roofs that I created by extrusion, but the behavior of the roof properties doesn't seem consistent.

On the first roof I created, I was in my South elevation, and used Grid C as my work plane. The roof properties shows -6" as the start offset, and 31'-0" for the depth. The resulting roof starts 6" towards my viewpoint in elevation, and then extends back away from my viewpoint 31 feet.

On the second roof, I was also in the South elevation, and used Grid B as my work plane. I wanted a similar roof, but longer. On this roof, I had to change the offset reference to positive 6", and have it extend negative 211 ft. to make it extend back away from my viewpoint, in the same direction as the other roof.

So what is the deal here? Both roofs extend away from my work plane in the South Elevation, but on one I had to make the Extrusion End parameter a positive value, and the other one I had to make it a negative value. Thoughts?

[sbrown]

Just a guess, but was one grid created left to right or top to bot and the other right to left or bot to top. Revit seems to take direction of object creation to give all object a pos side and neg side(front or back).

[patricks]

Hmm interesting, I didn't know that.

My boss made all the grid lines a couple of months ago so I don't know for sure, but that's probably the reason.

[dbaldacchino]

I think Scott is right. I read somewhere that even when it comes to Reference planes, Revit has a way of determining which side is positive and which is negative, which is important to know when doing extrusions. Now if only we could see this graphically and not have to remember it.....

[whittendesigns]

oh boy, I prolly shouldn't say I do this, but I just chuck it up there the best I can and go perpendicular to the view(or plan view works better) I just made it in and adjust the front and back of the roof to the planes I want and lock 'em.

So precise I am!