Does anyone have any idea what's going on here?
I have a family with a few parameter driven dimensions - see screenshots. The family is essentially to represent some cable hanging between two fixed points at various spans with varying amounts of sag (a circular curve approximates a catenary close enough for my purposes). The sag parameter is a % value of the span and controls the position of the center point for the arc and the radius of the arc. The end points of the arc are aligned to the horizontal reference line.
The parameters and geometry all work together fine at 10% as in the following example:
1. Sag at 10%.JPG
When I change the sag to 5%, everything still works:
2. Sag at 5%.JPG
When I change the sag to 2%, the arc decides to flip around and go the other way:
3. Sag at 2%.JPG
And of course when I change it back to the original 10%, it keeps the incorrect geometry:
4. Sag at 10% again.JPG
How on earth do I make Revit understand? And to make it more maddening, if I incrementally step the value down by 1 and apply it each time, it keeps the geometry correct, but if I change it straight from 5% to 2% it flips.