Reference planes have a property called Is Reference. By setting this property, you specify that the reference plane can be dimensioned or snapped to when you place a family into a project. For example, if you create a table family and want to dimension the edges of the table, create reference planes at the table's edges and set the Is Reference property for the reference planes. When you create dimensions for the table, you can then select the table's edges.
Is Reference also sets a reference point for dimensions when you use the Align tool. Specifying the Is Reference parameter lets you select different reference planes or edges of aligned components for dimensioning. The Is Reference property also controls if a shape handle is available on instance parameters in the project environment. Shape handles are only created on instance parameters attached to reference planes with strong or weak strength.
To dimension or snap to a location on families placed in a project, you need to define the references in the Family Editor. You set the reference plane attached to the geometry as either strong references or weak references.
- A strong reference has the highest priority for dimensioning and snapping. For example, you create a window family and place it into a project. As you are placing the family, temporary dimensions snap to any strong references in the family. When you select the family in the project, temporary dimensions appear at the strong references. If you place a permanent dimension, the strong references in the window geometry highlight first. A strong reference takes precedence over a wall reference point (such as its centerline).
- A weak reference has the lowest priority for dimensioning and snapping. When you place the family into the project and dimension to it, you may need to press Tab to select a weak reference, as any strong references highlight first.
- A not a reference is not visible in the project environment so you cannot dimension or snap to those locations in a project.
| Strong References | Weak References | Not a References |
|---|---|---|
|
Weak Reference | Not a Reference |
If you create multiple families with the same Is Reference value for a particular reference plane, the dimensions to that reference plane apply when you switch between family components.
Examples
- You create a table family and a chair family, and specify the left side reference plane property value to Left for both of them. You place the table in a building and dimension it from the wall to the left side of the table. If you replace the table with the chair, the dimension to the left side would remain to the left side of the chair because they both had a property value of Left.
- You create a toilet family and a sink family, and specify the left side reference plane property value to Left for both of them. You place the toilet in a building and dimension it from the wall to the left side of the toilet. If you replace the toilet with the sink, the dimension to the left side would remain to the left side of the sink because they both had a property value of Left.
To specify the Is Reference value:
- Click Create tab
Datum panelReference Line (or Reference Plane), and sketch a line or reference plane. - Select the line or plane, and on the Properties palette, for Is Reference, select Strong Reference. Note: The default reference property for all reference planes and sketched lines is Weak Reference.
- Click Apply.