How components work

Every Alien component runs one plain script file, in Python 3 or C#. The file lives in a folder you choose, so you can read it, edit it, share it and keep it. Save the file, or let Alien or an agent change it, and the component rebuilds its pins, keeps its wires, and runs again.

The header

Two comment lines at the top of the script give the component its pins:

divide_curve.py

# NODE_INPUTS: base:Curve, count:int | "divisions" min=2 max=200 default=20
# NODE_OUTPUTS: points, log
# CATEGORY: Geometry
# Divides a curve into N points.
import Rhino.Geometry as rg

params = base.DivideByCount(count, True) if base else []
points = [base.PointAt(t) for t in params]
log = f"{len(points)} points"

NODE_INPUTS and NODE_OUTPUTS list the pins. You can use several lines of each.
Each input is name:type, then optionally | "description" and settings: min=, max=, step=, decimals=, default=, options="a|b|c".
# CATEGORY: puts the component in a library category. The next comment line is its listing in the library.
In C#, the same lines start with //.

Pin names are how Alien keeps your wires. Rename a pin and its wires drop, so keep names stable.

Controls come from the header

Leave an input unwired and it gets a control right on the component:

The input is	You get
a number (`float`, `int`)	A slider. `min` and `max` set its range; without them, a range is suggested from the default. A fast script follows the drag live; a slow one runs when you let go
a `bool`	A switch
a `bool` with the word `button`	A momentary button: on for one run. Used for anything slow or paid, so re-running never repeats it
a `str`	A text field that grows as you type
a `str` with `options="a\|b\|c"`	A dropdown
a `str` with the word `image`	Drop an image on the component; it shows a thumbnail
a `str` with `suggest="vic-address"`	Victorian address suggestions while you type
geometry (curve, surface, Brep, mesh, point and more)	Select in Rhino (next beta): pick objects in the viewport, and the component follows them when they move or change

Wire something in and the control folds away to its pin. Values you set save with the .gh file and can be undone. Input dots: green means wired, blue means a value you set on the component (or an agent set), grey means the header’s default.

Types

float int bool str Color Interval Point3d Vector3d Plane Line Circle Arc Box Rectangle3d Curve Surface Brep Mesh SubD Geometry Transform object Add list[T] for a list, or tree[T] for a data tree, which arrives as a list of branches. Values arrive as plain RhinoCommon and .NET types. Outputs are the top-level variables named in NODE_OUTPUTS: a list becomes a Grasshopper list, and a list of lists becomes a data tree.

Reading a component at a glance

The component shows the Alien mark, the script’s name, a PY or C# badge and its state: ok, error or running. When a run fails, the error itself is printed on the component, not hidden in a log. The selected component glows.

Section	Items
Script	Edit, new, open, reveal, reload
Describe	Open the panel, stop
Inputs	Show controls, reset
Share	Copy the component’s id
Settings	Script repository, settings file

Where your files live

Your scripts live in the script repository: Documents/Alien scripts unless you choose another folder (right-click › Script repository). Your .gh files point to scripts relative to it, so a folder you share with a colleague works on their machine too. The ready-made components are copied into its suite/ folder. Alien keeps the ones you haven’t touched up to date, and leaves alone any you edit or delete. What the generators make is kept in .alien/assets/.

Scripts run inside Rhino with your user’s permissions, including ones a model writes and ones someone shares with you. Read a shared script before you run it.

Python and C#

Python
C#

Real CPython 3.9 inside Rhino 8. import Rhino.Geometry as rg. Add packages with # r: numpy near the top; Rhino installs them on the first run. Put shared helpers in helpers.py in your script folder and import helpers.

C# 9 script mode: using lines, then top-level statements, with inputs as typed variables. Add references with // r "nuget: Package, 1.2.3" or a full path to a DLL. Best for tight numeric loops, large data and parallel work.

Components in both languages mix freely on one canvas; the wires carry RhinoCommon types either way.

Get started

Using Alien

Ready-made components

Reference

How components work

The header

Controls come from the header

Types

Reading a component at a glance

Right-click menu

Where your files live

Python and C#

​The header

​Controls come from the header

​Types

​Reading a component at a glance

​Right-click menu

​Where your files live

​Python and C#

The header

Controls come from the header

Types

Reading a component at a glance

Right-click menu

Where your files live

Python and C#