Parametric Clearance based on Nested Family Type

[cole_went]

I am working on creating a family for a medical suspension system. The geometry all works properly and consists of a nested family with other nested accessories giving the user the ability to select the accessory from a Family Type: Specialty Equipment parameter. I am trying to add clearances to the family, one for the center access, and another for the accessory. I am able to create the center clearance easy enough because that is based on a simple length parameter for the arm of the suspension. I am struggling to figure out how to create a clearance for the accessory. The Image below shows the Ref. Level view of my family. The red circle is the center access, the Green circle is the accessory clearance.

Because the user can change the accessory, the accessory clearance needs to adjust based on the accessory selected. My thought was to create a "Clearance VAR" parameter, then use a formula for the clearance diameter that would add the length of both arms and the Clearance VAR (Arm 1 Length + Main Arm Length + Clearance VAR). This appears to be working correctly (Screenshot below):

I then tried creating a "Clearance VAR" parameter that would account for the differences between the different accessories. I thought I could use an IF statement formula to change the value based on the accessory in the Accessory parameter. The formula I was using is below:

if(Arm 1 Accessory = "UDM", 137 mm, if(Arm 1 Accessory = "Screen", 237 mm, if(Arm 1 Accessory = "SLX628", 442 mm, if(Arm 1 Accessory = "SLX528", 377 mm, if(Arm 1 Accessory = "NFC-SLX628", 758 mm, if(Arm 1 Accessory = "NFC-SLX528", 663 mm, if(Arm 1 Accessory = "NAV Cam", 199 mm, if(Arm 1 Accessory = "Lead Shield", 161 mm, if(Arm 1 Accessory = "Bubble Cam", 173 mm, 0 mm)))))))))

I can't seem to get this formula to work, I'm not sure if the formula is incorrect, or if there is some limitation in Revit that doesn't allow this type of formula to work with Family Type parameters. I've attached the family to this post. 

Any help or direction would be greatly appreciated! 

[barthbradleypdq]

Text cannot be evaluated in formulas. Only numeric and Yes/No parameters. Lookup Table might be a way to go though. 

https://help.autodesk.com/view/RVT/2024/ENU/?guid=GUID-91270AEF-225A-49D7-BF84-1F44D1E3E216

[ToanDN]

Create an integer parameter and use a number for each accessory type, then use this integer parameter in the formula.

[azad.Nanva]

make the parameter

"UDM<Specialty Equipment> (default)=Type:UDM"

"Screen<Specialty Equipment> (default)=Type:Screen"

and you can use it in formula :

if(Arm 1 Accessory = UDM, 137 mm, if(Arm 1 Accessory = Screen, if(Arm 1 Accessory = SLX528,337 mm,0 mm))))

i don't have 2022 anymore to fix your family if you see the screenshot , i think you can understand what i did.

if not tell me to explain more.

[Mike.FORM]

As @azad.Nanva posted the correct way to accomplish what you want is by using additional "family type" parameters, one for all the nested options you can switch between. Set each of them to the differing types and make sure users know not to change them.

Then you can compare these helper family type parameters to the family type parameter you are actually using to switch out the nested families.

[cole_went]

@azad.Nanva and @Mike.FORM  thank you both for your responses! I'm not familiar with this technique, can you elaborate a little more on how this would work or direct me to another thread if that is easier for you? 

[Mike.FORM · Accepted solution]

I do not have 2022 but this is a simplified example of the parameters for a sample family. It has 3 types for a nested family (triangle, square, circle) which is controlled by a family type parameter called "shape".

There are 3 more family type parameters as shown in the image to compare against in the formula driving the size.

[azad.Nanva · Accepted solution]

watch the film and test your family:

[cole_went]

@azad.Nanva and @Mike.FORM you are my heroes! This worked great. Thank you both so much for your help!