Trig Driven Roof Family

[jpolding]

Warning: Not for the faint of brain...

Greetings. I had started this thread originally but it got lost in time before I could find an answer. Any help is truly appreciated, in the form of beer at AU...:beer:

I've attached an image explaining the question and the Revit file. It's more of a trig question than a Revit one but it all ties together.

original thread...
http://forums.augi.com/showthread.php?t=118549&page=2

[MatrimA]

Hi,

Couldn't help but take a look at this one. It's a very intriguing equation for me, as I am in the middle of writing a reference manual on compound roof joinery for timber frames. I'll look at it some more this weekend. Just wanted to point out or question that there appears to be one more driven variable....as I see it the length of the roof must also change to accomodate the coplanar z constraints.

cheers,


Matt

[jpolding]

Hi Matt,

Thanks for the response, sounds like you might know a thing or two about this. I'm curious to find out what you find out...

I was only able to take it this far but it's not mathematically perfect because we couldn't figure out the trig formula.
A friend of mine was able to help me make a a polynomial equation in Excel graph based upon X and Y points.

Here's the equation.
y = 0.003x2 + 0.459x + 11.98

[crispin.schurr]

Hi Jay

There is no correlation between the 2 angles, given the units you have here.

Indeed any combination of angles is possible, by adjusting the lengths of the protruding lower edges of the inclined flap, to align the lower elevated corner vertically over the original lower roof corner.

Hope this helps

C

[DoTheBIM]

Is the 100.48 angle fixed?

[jpolding]

Yes, the 100.48 angle is fixed. That's the only angle which is fixed. The front edge of the roof in question needs to line up with that angle not matter what the X angle is.

[jpolding]

Thanks for your input!

Another way to describe this is:

The front edge of the roof flap must always be coplanar with the 100.48 Z.
Angle X can and will change to a precise angle.
In order for this change NOT to affect the coplanar Z, the Y angle will have to change. This is because the flap is square to itself, 90 degrees at the corners.

[DoTheBIM]

I'm pretty sure I understand what you trying to do geometrical wise... and thiink I could eventually work out the trig... maybe... but it seems that there would have to be an easier way with different variables/constraints. 'Tis difficult to to see alternative ways to do something given the very limited info. I'm sure there are reasons that you might not be able to disclose why it is the way it is but if you can it might help if one understood the logic for arriving at the current way things are set up.:beer:

[DoTheBIM]

Need to confirm....

From your pic...

Goal: Set X to get Y value

100.48° is fixed

90° is fixed on the flap & all four corners are 90°

Roof pitch (Fixed Roof plane) is fixed @ 27.6877747188°

X angle is NOT coplainer with the fixed z coplaner lines and is perpendicular to the flap as it is defined in the flap parameters.

The front edge (Top side) must be coplaner with the Fixed Z coplaner lines, thus implying that the flap length along the Y angle will vary accordingly so that the front corner point is always in plane with the labled z lines??? Otherwise the front edge line could merely be parallel and not coplaner depending on the length of the flap.

[jpolding]

You've got it. This is a project that I'm working on but can't show the full building yet. I was able to use a chart based formula along with the align function in Revit but it just doesn't have the elegance of trig. Often I've been able to use other means to get static forms that I want but not so when it comes to something truly parametric. I need to learn trig, I can see that, but I need to go back to basics. From what I can see, this problem is not very basic. Thanks again for taking the time to look at this.