Looking for tricks to lock Ref Planes to round objects

[vanderloo5]

I'm creating a round fixed window family and, after cutting the round opening into the wall, I'm attempting to have a top, bottom, and 2 side reference planes locked to the opening. I've been wrestling with this for over an hour and I can't seem to figure out how to lock these ref planes to the right, (or any), area on the circular opening.

[David_W_Koch · Accepted solution]

I am not certain that you can align and lock a circle to a reference plane.  But you can achieve the same effect by driving both the circular opening and the position of the bounding reference planes by parameters that are tied to each other.

In a test file started with the Revit 2025 out-of-the-box Imperial Window family template, I added a Center (Elevation) reference plane, and locked it EQ-EQ between the Top and Sill Reference planes.  Then I edited the opening cut, deleting the straight lines that were locked to the Top, Right, Sill, and Left reference planes.  I added a Circle with the center at the intersection of the Center (Left/Right) and Center (Elevation) planes and drew the radius of the circle to the intersection of the Center (Elevation) and Right reference planes.  I selected the Circle and turned on the display of the center mark by checking the toggle for the Center Mark Visible parameter, under the Graphics category in the Properties palette.  I then used the Align tool to align and lock the center mark to the Center (Left/Right) and Center (Elevation) planes.

I created a new dimension parameter, called Radius.  I placed a radial dimension on the circle for the opening, and labeled it with the Radius parameter.

I then finished editing the Opening Cut Boundary.

In the Family Types dialog, I set the Height equal to the Width, and the Radius equal to half of the Width.

Now a change to the Width, Height, or Radius will percolate through all of them, keeping the Top, Right, Sill, and Left reference planes tangent to the circular Opening Boundary.  That is the equivalent of locking the circle to those reference planes.  I have attached my sample file (done, as previously mentioned, in Revit 2025).