Reference Dimensions

By default, the dimension drives the geometry. If a line segment is constrained to have a length of 20.00 mm, then the line segment is modified until that length is accurate.

A reference dimension is the reverse: the geometry drives the dimension. If a line segment has a reference dimension on its length, then it’s still possible to freely change that length, and the dimension displays whatever that length happens to be. A reference dimension does not constrain the geometry.

To convert a dimension into a reference dimension:

• Choose Constrain ‣ Toggle Reference Dimension.

A reference dimension is drawn with ‘REF’ appended to the displayed length or angle. Double-clicking a reference dimension does nothing; the dimension is specified by the geometry, not the user, so it is not meaningful to type in a new value for the reference dimension.