Formula-Driven Types

Would you like to make families that can change Types based on a parameter?  For example, say you have a table family that contains a nested chair family.  If the table is larger than, say, 60” diameter, you’d like it to automatically use a different chair.  Here’s how you can do this in Revit 2012:

1. In the AppMenu, click Open > Family.  Navigate to the Furniture folder and open Table-Dining Round w Chairs.rfa. 
2. In the Insert tab, click Load Family.  Navigate to the same folder and load Chair-Task.rfa.
3. In the Modify tab, click the Family Types button. 
4. In the Family Types dialog, click Parameters: Add…
5. Create a new Type Parameter named, say, T (for Chair-Task).  Set Type of Family as <Family Type…> with category Furniture.  OK.
6. Repeat steps 3 through 5, but name the parameter B (for Chair-Breuer, the default chair in the Table-Dining Round w Chairs family).
7. Select one of the chair groups (it’s a group because it has been arrayed around the table in this family), click Edit Group, then select the chair.
8. In the Options Bar, choose <Add Parameter…> from the Label drop-down.
9. In the Parameter Properties dialog, name the new parameter L (for Lable).  Click OK.  In Edit Group, click Finish.
10. In the Formula cell for Parameter L, type in “L = “if (Diameter>5’, T, B)”.
11. Now, you can try your new formula-driven type by flexing the family:  Change the Value of the Diameter parameter (try 4’, then 6’) and see the chairs change when the table gets larger than 60".