Controlling Arcs for Arched Top Windows

[3dway]

I'm hoping that someone has a method for this, or knows which formulas work with the way that Revit manipulates sketch lines.

Ex.

We have arhced top windows which are defined by the length of the vertical leg at the side of the window, and by the overall rise from the end of the vertical leg to the peak of the arch.

The relevant formula is likely going to be something to do with a chord.

Anyone?

I'm not able to make flexing families for my arched top windows because when I flex the width, the arches go all squirrely.

[cliff collins]

Perhaps try this approach: ( if said arch is a "roman arch"--not parabolic?)

Make a reference plane vertically down the centerline of the window.

Create a dimension parameter for the radius of the arch top

Place a dimension and snap to the vertical leg/tangent of the arch and the centerline ref. plane and apply Equal lock.

The arch should then flex when width of window changes.

Is this what you are after?

How does the OOTB Archtop window handle this, or maybe one of the Anderson
families?

cheers............

[bwbarch]

I have found the "Ask Dr. Math" website invaluable for finding the right formulas to drive circles, triangles, etc. in families. What I appreciate is their "if you know A and B, here is how to find C" approach to explaining the formulas.

One of the challenges our office has faced with developing arch top windows is determining the best way for the user to specify the geometry of the window. For instance, some window manufacturers specify the arch by its radius, and some by the "shoulder height." I have run into situations where knowing the radius is most useful, and others where the shoulder height is most useful. Our office settled on specifying the shoulder height, but you could just as easily set up parameters to control the top-of-vertical-leg-to-top-of-rise as you have expressed. I suppose other combined approaches with YES/NO parameters could be tried, but such efforts can get overly complicated in a hurry.

All that said, here is an example of a generic window opening that should demonstrate the concept. I have used a curved reference line (colored red) to provide the appropriate "skeletal component" of the arch. But here is a great tip that has been a real sanity check for me on more than one occasion: If you select the curved reference line and open its properties window, check the check box for "Center Mark Visible". That center mark can then be aligned and locked to reference planes to enable you to control the location of the center point of the arc relative to other parts of the window. BTW, this works with sketch lines and regular lines as well.

The formula that drives the radius of the arc came from the Dr. Math website, and I translated it into Revit-speak. Essentially this process is a replication of placing a 3-point arc as you do with the Detail Line tool.

[3dway]

Thank You.

I clearly need to read up on formulae in Revit.

[twiceroadsfool]

http://malleristicrevitation.blogspot.com/2007/10/trigonometry-revit-parameters-and.html

I wrote a few posts about it, because i/we had a few problems getting it to work. Its certainly overly complex, because we wanted some extra information out of the family. But the chart is in there that has all the geometry formulas youll need...

[3dway]

Can you dimension an offset between arches in the family editor?
I can see that I wouldn't want to recreate a bunch of "if then" formulae to control, the trim, the sash, all of the other lines that are concentric with that reference line.

[twiceroadsfool]

Seems to me you would just use a Length Parameter = to something like "RADIUS + OFFSETPARAM" or whatever... If youre just talking about concentric arcs...

[bwbarch]

To elaborate on twiceroadsfool's point, the method we used was to locate the subsequent arcs of the window componenets, i.e., sash, trim, etc., at the same centerpoint as that used by the arched reference line. There is no way to dimension offsets between arcs, but you can produce concentric arcs by calculating their radii in relationship to the curved reference line, and then locking their centerpoints all to the same reference point.

For instance, if you were to set up a sweep for arched casing, you would set that sweep's curved sketch line centerpoint to the same intersection of reference planes as those used by the red curved reference line. Then, you would need a simple calculation to determine the radius of that sketch line arc as compared to the radius of the reference line. So, let's say you had a 3/4" thick window frame whose outermost curved edge is set to the curved reference line, and the casing's reveal from interior finish edge of frame is 1/4". The radius of the casing sweep would be 1/2" less than the radius of the reference line. All this would be driven by simple add-and-subtract formulas (no need for IF/THEN's) based on your assumptions of the casing reveal, frame thickness, etc.

We have also used this method successfully with nested families by linking the radius location point in the nested family through to the host familiy's parameter that drives the red reference line's location. All components stay in sync as the family is flexed.