Here's a nice tip from Bruce Madsen in the San Francisco office that was used to allow for a quick positive or negative distance value to adjust curtain panel offsets:
The problem is that Revit does not allow negative distances:
When a negative distance is entered, Revit will report, “Parameter <name> has an invalid value.”
Create the Offset parameter as a number and use an IF statement to control the length – and to convert the number to a distance.
Steps to Follow:
- Create a “Number” type parameter for the offset dimension
- “MyOffset_Inches”, in this case
- The formula will assume inches, so we added “Inches” to the name
- In words, to calculate the Variable Length;
- If the Offset is negative, subtract the absolute value of the Offset from the Base Dimension
- If the Offset is zero or positive, add the value of the offset to the Base Dimension
- In the formula, note the multiplication by 1”. This is to convert the Offset (Number) parameter to a distance.