Core concepts
The four tabs
The editor panel is the whole tool. Everything you build lives under one of four tabs, and each tab is one lane of the saved family:
| Tab | What it holds |
|---|---|
| Parameters | The inputs that drive geometry — Width, Height, a material, a yes/no… |
| Types | Named size variants — preset value sets the user picks in Revit. |
| Materials | The family's own Revit materials (colour, transparency) and its subcategories. |
| Generators | The geometry elements (headed Elements): shapes, forms, curves, arrays, annotations… |
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, reference planes, text, annotations, MEP connectors, nested families.
Material/Subcategory— the family's own Revit materials and subcategories. They are not elements: they live in their own lists and a form points at one by name.
Parameters drive everything
Each parameter has a key (its name) and a type (length, number, angle…). It holds no value of its own: it is either computed by a formula, or set per family type — exactly as in Revit. 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. Its material, subcategory, visibility and detail levels are its properties — each one either a fixed value or a parameter Revit lets the user change.
Types are size variants
A family ships with named types, and a type is where parameter values actually live — so every family has at least one. A door might ship 800 × 2100, 900 × 2100, 1000 × 2100, each a full set of values. 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.