Getting started#

Open the app. The workspace has three columns:

• Left — the family catalog (click one to open it) and a New button (creates a blank family instantly with the Metric Generic Model template).
• Middle — the 3D viewport, showing your family live.
• Right — the editor panel: a toolbar plus three tabs, Parameters, Types, and Generators (where the geometry lives — its list is headed Elements).

Build a door panel, step by step#

This walks the whole loop once. Every control named below is a real button in the panel.

1. Start a new family. Click the 📄 New button in the toolbar (not the one in the left catalog — that skips the dialog). Name it, pick a template (Metric Generic Model is fine), Create. Parameters and Generators start empty.
2. Add the driving parameters. On the Parameters tab click + and choose Length. A row appears — click its key and rename it Width. Click the row's ⚙ and set Default value to 900, tick Instance so it is editable on each placed door. Repeat for Height (default 2100) and Thickness (default 45).
3. Add a derived parameter. The panel sits centred, so we need half its height. Add another Length, rename it HalfHeight, and in the row's formula field type Height / 2. (Math lives in formulas, not in geometry fields — see Parameters & coordinates.)
4. Draw the profile. Switch to the Generators tab. Click +, and under SHAPE pick Rectangle. A rectangle element is added.
5. Make it follow the parameters. Click the rectangle row to select it — its fields expand. Each coordinate field has two buttons, V (a fixed value) and P (follow a parameter). For width click P and choose Width; for height choose Height; for the center's Y choose HalfHeight. Leave center X on V = 0.
6. Give it depth. Click + again and under FORM pick Extrusion. Select it; in the profile checkbox list tick your rectangle, and set depth to P → Thickness. You now have a 3D door panel.
7. Tune it live. Back on Parameters, change Width to 1000 — the panel widens in the viewport instantly. That is the whole parametric loop, before Revit.
8. Add size variants (optional). On the Types tab add named types like 900 × 2100 with preset values — the user picks one when placing the family.
9. Save / export. Save JSON (the disk icon) stores the family. To produce the real .rfa, open the family in the Molding Revit plugin and press Generate (the ▶ icon).

In the browser you design and preview. The actual .rfa is produced by the Molding Revit add-in — this same editor inside a Revit panel, where the Generate button is enabled.

Grab it from the Revit Plugin page. New to the V / P toggle? It is the core idea — read Parameters & coordinates next.