Virtual Columns (V-Cols)
The flagship feature of the Logic & Rules engine is the Virtual Column (V-Col).
In native Revit, if you want to multiply a door’s width by its height, you have to use a Calculated Value. If you want to merge a Family Type name with a Manufacturer name, you have to use a Combined Parameter. Both dialogs are rigid, notoriously prone to syntax errors, and cannot be mixed together.
V-Cols replace both of these native Revit features with a single, unified Formula Builder. Because V-Cols are processed entirely within the Vellum engine, you can generate an unlimited amount of custom schedule data without cluttering your Revit project with one-off shared parameters.
The Formula Builder
Section titled “The Formula Builder”Instead of forcing you to type out exact parameter names and risking typos, Vellum uses an interactive “Pill” based interface.
You simply click the parameters and math operators you want to use, and Vellum automatically color-codes them based on their data type: green # pills for numbers, and grey Aa pills for text.
Toggle through the examples below to see how Vellum handles Math, Text, and Mixed data types:
Virtual Columns (V-Cols)
Live Preview and Error Checking
Section titled “Live Preview and Error Checking”Writing formulas in Revit is often a guessing game. You write the formula, click “OK”, and hope Revit doesn’t throw a “Inconsistent Units” error.
Vellum’s Formula Builder features a Live Preview block at the bottom of the editor. As you build your V-Col, Vellum silently evaluates the formula against the first row of your schedule data in real-time. If the logic fails or results in NaN (Not a Number), Vellum will immediately flag it, allowing you to fix the formula before you ever publish the column.
Simple Logic vs. Complex Logic
Section titled “Simple Logic vs. Complex Logic”The V-Col Formula Builder is intentionally designed to be lightweight and fast, covering 90% of standard architectural schedule needs (basic math, unit conversion, and string concatenation).
However, if you need to execute highly complex logic—such as nested IF/THEN/ELSE statements, multi-category relational queries, or advanced regex string manipulation—you should bypass the standard V-Col builder and use the Nodes Studio.
(When you build a new column inside the Nodes Studio, it will automatically appear in your Content Drawer as a standard V-Col!)