I'm not sure if this is a problem with Revit's solution finding algorithm or if it's my modeling skill, but since I've been modeling in various software for 18 years, I think it's Revit.
I opened a new family file with a generic template and created a circle with the center on the two reference planes. Then I created another circle to the right centered on the front/back reference plane and another circle above the first two circles and between them. I wanted to have an equal 7" measurement between all circles (center to center). I dimensioned them center to center and then as a changed the dimensions, Revit randomly changed other dimensions instead of finding a solution that did not require changing other dimensions. I tried locking dimensions which worked at first but when I had two dimensions locked at 7" and changed the third dimension to 7", it said a solution could not be found. It also gave the same error message when I dragged either circle with an unlocked dimension. It didn't keep the two dimensions locked and let the circle pivot around the center of another circle. But when I tried it with one locked dimension, I was able to move one circle around until the other two dimensions read 7" and then released and everything was okay. I locked the two dimensions and now it's fine. so there clearly was a solution and Revit couldn't find it. It doesn't seem to understand degrees of freedom.
Is Revit MEP 2010's solution finder better? (Not that I can use it right now since the other contractors I am working with are all using 2009).
