Core concepts
The three tabs
The editor panel is the whole tool. Everything you build lives under one of three tabs:
| Tab | What it holds |
|---|---|
| Parameters | The inputs that drive geometry — Width, Height, a material, a yes/no… |
| Generators | The geometry elements (headed Elements): shapes, forms, curves, arrays, materials… |
| Types | Named size variants — preset value sets the user picks in Revit. |
In the Generators list, click an element to select it — its argument fields expand inline right under the row. That expanded panel is where you wire the element to parameters.
A family is a graph, not a mesh
A Molding family is a small definition: a list of parameters and a list of elements. It is not a baked mesh — it describes the geometry parametrically, so it stays tiny, editable, and easy to generate. The browser evaluates it into a preview live; the Revit runner evaluates the same definition into a .rfa.
Parameter— an input value that drives geometry: a length, count, angle, material, yes/no…Shape/Segment— 2D building blocks: closed profiles (rectangle, circle, loop) and the open curves (line, arc, spline) that build them or guide a sweep.Form— a 3D solid or void built from profiles: extrusion, blend, revolution, sweep, swept blend.- Helpers — arrays, transforms, materials, reference planes, text, annotations, MEP connectors, nested families.
Parameters drive everything
Each parameter has a key (its name), a type (length, number, angle…), and either a default value or a formula that computes it. In a geometry field you flip the P toggle and pick a parameter, so changing one parameter ripples through the whole family. This is the heart of Molding — covered in detail under Parameters & coordinates.
Profiles become forms
A Form takes one or more closed profiles and gives them a third dimension:
| Form | Built from |
|---|---|
| extrusion | one profile + a depth |
| blend | a bottom profile + a top profile + a depth (a loft between two shapes) |
| revolution | a profile spun around an axis |
| sweep | a profile pushed along a path curve |
| sweptBlend | two profiles morphed along a path |
Every form can be a solid (the default) or a void that cuts other geometry, and can carry a material.
Types are size variants
A family ships with named types — preset parameter values. A door might ship 800 × 2100, 900 × 2100, 1000 × 2100. The user picks one when they place the family; instance parameters can still be tuned per placement.
It becomes a real .rfa
Molding generates the full constraint apparatus — reference planes, dimensions, and parameter associations — so Revit's built-in solver drives the recompute. The generated Family Editor is dense, but nobody reads it: the node graph is the surface you work in, and the .rfa is a generated artifact, not meant for hand-editing.