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Intro to Grasshopper


In this guide we will introduce the computational design tool Grasshopper and discuss both how it works as well as how it can enable a new way of thinking about design. By the end of this guide you will understand what Grasshopper is, how to get it running, and will be ready to start developing your first Grasshopper definition in the next exercise.

Tutorials in this series:

Getting Started With Grasshopper
1Intro to Grasshopper
2Exercise: Hello Grasshopper!
3Working in Grasshopper
4Exercise: Parametric tower
5Working with Data
6Exercise: Parametric facade

What is Grasshopper?

Grasshopper is a visual programming environment built on top of Rhino, a CAD program. It enables you to design by establishing relationships among data and modelling operations instead of directly manipulating geometry. This allows designers to think systematically, rather than focusing on static objects.

Like any programming environment, Grasshopper allows you to create algorithms, or sets of instructions, for telling a computer what to do. In traditional programming, these instructions are written using programming languages, text-based systems that follow strict formatting rules and have specific vocabularies for describing computer operations. With visual programming, the instructions are described in a visual interface using a set of nodes, or components, that describe operations, and a set of lines, or wires, that create connections between them. The layout of these components and wires is stored in a visual script or definition that can be visualized and edited in the Grasshopper canvas.


Visual programming (left) and text-based programming (right)

In mathematical terms, you can think of the nodes as functions which take in inputs and generate outputs. The wires then are the way in which data is passed between the inputs and outputs of different functions. Although text-based and visual programming do basically the same thing, a visual interface can be easier to learn and more intuitive to use for designers, who tend to be more visually oriented and don't typically have a background in coding.

Thinking systematically

Forgetting design for a moment, let’s consider how we could use visual programming to describe a simple formula: y = 2x + 3:


Going in the order of operations, you first pass a variable x and the number 2 into a function that multiplies them together. Then you take the result of that function and the number 3 and pass them into another function that adds them together. The result of this function will be the solution to the formula, y. In Grasshopper, the definition would look like this:


Pretty straight forward, huh? It’s amazing that all Grasshopper definitions are composed of only these two types of elements: components that define small operations that do stuff, and connecting wires that pass information between the components.

Since Grasshopper is a design tool, it cannot be limited to simple mathematical operations. Luckily, since Grasshopper is built on the 3d modeling software Rhino, it has access to all of the geometric functions contained within Rhino, and allows us to access these functions within our definitions. The combination of its intuitive visual programming interface with Rhino’s best-in-class geometry library makes Grasshopper a powerful tool for computational design and by far the most popular computational design tool used today.

How does Grasshopper connect to Rhino?

Like most computer software, Rhino has two components — the front-end graphical user interface (UI) with which users interact, and a backend system that contains all the logic for what the program can do. In a CAD program like Rhino, the front-end contains the visual display of the geometry and a command-input system that allows users to run commands to generate geometry while providing inputs and getting visual feedback from the display. On the backend, there is a library that defines the functionality behind all of the geometric commands, along with other functionality needed by Rhino such as saving and loading files.


Like many modern software, Rhino exposes its backend system through an Application Programming Interface (API), which allows third-party developers to build functionality on top of Rhino’s backend system while bypassing the front-end user interface. Grasshopper utilizes this API to expose the geometric operations as individual components, allowing users to craft their own automated workflows using Rhino’s backend. The Rhino API and how it is used by both Grasshopper and Python will be discussed in detail in a later section.

Designing with algorithms

When you first learned how to model geometry in a CAD software, you probably used a visual UI to perform many of the operations. For example, if you wanted to make a box, you would run the “box” command, which would give you a series of instructions to follow for making the box. First, you would click on a point in space to specify the first corner of the box, then click another point to specify the other corner of the base, and finally use your mouse to visually define the height of the box. This is a very visual and intuitive way of making geometry in the computer, and matches the traditional way of working with physical materials by hand to create form.


Box created in Rhino using the visual interface

If you wanted to be more precise about the geometry, you could start to enter exact values for some of the dimensions. For example, you could specify exact coordinates for the base point of the box. You could also use the desired width and length of the box to calculate the second corner point, and finally enter an exact height for the box. Now the box is precisely defined through data, without relying on any intuitive input. Most designers use a combination of these two methods:

  1. Intuitive visual modeling for generating initial concepts, and then
  2. Adjusting exact dimensions as the model is refined


Box created in Rhino based on exact dimensions

When you work with computational models, you have to define everything about your design through data and functions, without relying on a visual UI at all. Creating form this way can be a challenge for many designers, since it requires not only knowledge of computational design tools such as Grasshopper, but good working knowledge of fundamental geometric concepts such as vector math and trigonometry, which are not typically taught as required courses in design schools.


Box created in Grasshopper by defining a system of variables and operations

Towards Computational Design Thinking

The goal of this course is to give you just enough background on these topics so you can get started with Grasshopper, and continue to develop your knowledge over time with more intermediate and advanced courses. However, once you get past the initial technical learning curves, true success with computational design relies not just on knowing the tools, but also in a change in how you think about design itself.

Traditionally, design was a highly intuitive and visual process, where the designer started with a base material and crafted it through a series of operations while getting direct visual feedback about what they were designing. With computational design, things are a bit different. Since computational design involves designing systems and not objects directly, there is not always the direct physical input or visual feedback to guide the process. Instead, computational design requires the designer to think of design problems systematically, break them down into smaller solvable parts, and then solve those smaller problems using the computational tools (such as Grasshopper) that they have at their disposal.

Because of its reliance on math and connection to computer programming, computational design is often thought of as more analytical and less intuitive than traditional design methods. However, there is still a large amount of intuition and creativity involved with designing computational models properly to ensure that they achieve the desired outcomes.

This change of mindset, or learning to think through design problems analytically, systematically, and computationally, is often called Computational Design Thinking. This new way of thinking about design relies on learning some new technical tools such as computational geometry and computer programming, but it goes far beyond that. Learning the tools and techniques of computational design will not only make you a more skilled designer, but will give you a new way of thinking about design and your creative process.

The Grasshopper community

One of the best features of Grasshopper, and one of the key factors behind its success, is the amazing community of designers and programmers that’s grown around it.

Designing computationally can be a very challenging and creative process. When you are building something totally new there are not always standard answers out there for how to solve the problems you might run into. In such cases it is useful to have a strong community of fellow users who can share experiences and help each other to overcome challenges in a collaborative way.

Because of its connection with computer programming, computational design inherits a lot of the community and open-source culture of the software development industry. A great way to engage with the Grasshopper community is by visiting the Grasshopper forum:

At this point, Grasshopper is old enough and the community of users is large enough that you can usually Google Grasshopper + whatever your issue is and get results from the Grasshopper forum (or occasionally private blogs or video tutorials) discussing the same issue.

Getting started in Grasshopper

Grasshopper started its life as a plugin for Rhino which you had to download and install separately. Since version 6, Rhino now has Grasshopper built-in, so if you are using Rhino 6 or later, you don’t need to install any additional software to use Grasshopper. You can start Grasshopper either by clicking the Grasshopper button in the toolbar or by typing Grasshopper in the Command line.


When you start Grasshopper, it will open up in a new window on top of your Rhino interface. The Grasshopper interface consists of two main parts: the components library at the top, and the canvas below.


The components

The components library contains all the components that are available to use in your model. Grasshopper comes pre-loaded with a large number of basic components, and you can also download libraries of custom components made by other users (more on loading libraries later). Each component is represented by an icon in the toolbar, and they are organized according to their function or the library they come from.

The canvas

The canvas is the most important part of Grasshopper. It is the visual environment in which you develop your Grasshopper models. To create a model, you drag components from the top toolbar onto the canvas, and then connect them together with wires by clicking and dragging between an input and output node.


You can think of the Grasshopper window as a separate "view" into your Rhino file. The Grasshopper model developed within the canvas has a connection to the Rhino model from which it was launched, so you should think of both Rhino and Grasshopper working together in a common environment, using their own separate interfaces.

When you develop geometry in Grasshopper, you will see this geometry visualized within the Rhino viewport. You can also reference objects from Rhino into your Grasshopper definition. With certain objects like points, you even get an interactive widget that allows you to move the Grasshopper geometry directly within Rhino.


Any geometry developed within Grasshopper is considered "dynamic geometry" because it does not actually exist in the Rhino model, but is only displayed for preview purposes in the viewport. Because of Grasshopper's connection to the Rhino model, however, you can take any geometry developed in Grasshopper and "bake" it so it becomes a permanent part of the Rhino file.


Because Grasshopper has its own interface and stores its own data, the definitions you develop in Grasshopper need to be saved to a separate file which usually has the extension .gh or .ghx. This file is separate from the .3dm file which contains your Rhino model data. This means that when you are working with Grasshopper, you typically are working in two separate files: a Rhino document and a Grasshopper model that is connected to it.

That concludes this module, congrats! Now that you have Rhino and Grasshopper open, go on to the next exercise, where we will build our first Grasshopper definition.