Monday, December 14, 2009

REVIT Calculating Standard Roof Slopes by Formula

As I start to get deeper into the conceptual parametric massing families I am coming up with all kinds of cool tips.
Here's a great one.
When you need to constrain reference lines in order to create down stream roof slope parameters for a conceptual mass form as in 3-12, 5-15, 7-12 etc. . . . You don't want the user to have to input the roof slope by an angle. You want to input the slope as a factor of Rise / 12 as shown below. This involves a little trigonometry. Remember the old tan (x) = opposite over adjancent ?
If not have a look at the images just below.
So we know the Adjacent (12) and the user inputs the Opposite (Rise) but the trick is we have to use the 'Inverse Tangent' to get the actual angle in degrees. Otherwise all we get is the Tan of the angle, not the actual angle itself. So the correct term for Inverse Tan is ArcTan which REVIT accomodates as the built in operator atan.
So have a look at the desired constrain resultant and the corrisponding parameter formula below.
The user inputs a Roof Rise of '7' and REVIT calculates the slope angle and adjusts the reference lines (and corrisponding solid form) accordingly.
It is also critical that the 'Slope' parameter is type 'Angle' and the 'Roof Rise' parameter is type 'Number'.
Once this flexes (balances) correctly you simply turn the reference lines into a solid form and Bob's Your Uncle !
Don't forget about the CADclips coined 'Brains', 'Bones', 'Balance' 'Body' approach to Family creation. Be it conceptual massing or conventional Familes.


Anonymous said...


Daryl Gregoire said...

Well, I hope that's a good comment?