Introduction to Grasshopper
Grasshopper lets you design with rules instead of fixed geometry. Build your first parametric definitions and learn the core ideas: components, data flow, lists and trees.
In this lesson you will
- Understand components, parameters and wires
- Build a parametric definition with sliders
- Work with lists and understand data trees
- Bake results to Rhino
The canvas
Type Grasshopper in Rhino to open it. You place components (operations such as Divide Curve, Circle, Extrude) and parameters (containers for geometry and numbers) on the canvas and connect them with wires. Data flows left to right; the preview appears in Rhino in red/green until you bake it.
A first definition: a row of columns
- 1Reference a Rhino line into a Curve parameter (right-click › Set one Curve).
- 2Add Divide Curve; connect the curve; add a Number Slider for the count.
- 3Add Circle with the division points as centres and a slider for radius.
- 4Add Extrude with a Unit Z vector multiplied by a height slider.
- 5Move the sliders and watch columns update; right-click Extrude › Bake to create Rhino geometry.
Lists and data trees
Most components process lists: 10 points in, 10 circles out. When lists are nested — e.g. points on several curves — Grasshopper uses data trees (branches of lists). Use Panel and Param Viewer to inspect data; Flatten, Graft and Simplify reshape trees. Understanding data structure is the key skill in Grasshopper.
Attractors and rules
A classic exercise: a facade grid of openings whose size depends on distance to an attractor point — near the point, openings are small; far away, large. Use Distance, Remap Numbers and Scale. The same pattern drives shading, structure sizing and panelisation.
Good habits
Group and label parts of the definition, use clear slider names and ranges, keep inputs on the left and outputs on the right, and save versions. Plug-ins extend Grasshopper for analysis and fabrication — download them only from their official sources (e.g. Food4Rhino).
Quick reference
| Command / tool | How to start it | What it does |
|---|---|---|
| Grasshopper | Rhino command line | Opens the editor |
| Number Slider | Params › Input | Adjustable numeric input |
| Panel / Param Viewer | Params › Input / Util | Inspect data |
| Bake | Right-click component | Creates Rhino geometry |
Common mistakes
Orange component with warnings.
Hover to read the message; usually a missing or wrong type of input.
Unexpected matching between lists.
Inspect trees with Param Viewer; graft or flatten as needed.
Exercise
Attractor facade
- Create a rectangular surface for a facade.
- Divide it into a grid of points (e.g. SubSrf or Divide Domain²).
- Draw circles at each point with radius driven by distance to an attractor point (remapped to 100–600).
- Move the attractor and watch the pattern change; bake a version.
You should end up with: A parametric facade pattern controlled by one point.
Checklist
0 of 5 checked · saved on this device
Lesson quiz
What does 'baking' do?
Finished this lesson?
Taking the quiz marks it complete too. Your course page picks up where you stopped.
Free KitWren tools that help
- Length ConverterConvert between metres, centimetres, millimetres, kilometres, inches, feet, yards and miles.
- Angle ConverterConvert degrees, radians, gradians, arcminutes and turns.
- Area ConverterConvert square metres, square feet, acres, hectares and more.
- Image ResizerResize images to exact pixel dimensions or by percentage, keeping the proportions if you like.
- Merge PDFCombine multiple PDFs into one file, in any order, choosing which pages to include from each.
Free, independent learning material written for KitWren. Rhinoceros, Rhino and Grasshopper are trademarks of Robert McNeel & Associates. KitWren is not affiliated with, sponsored or endorsed by Robert McNeel & Associates. We never provide software downloads, licence keys or cracks — use the official sources.