1st March 2024

GHEC 01 : The Grasshopper and Rhino Relationship

Today’s focus:

  • The Grasshopper and Rhino Relationship
  • The Grasshopper Interface
  • Getting Components
  • Visualizing data in Rhino
  • Homework to complete before the next session

The Grasshopper and Rhino Relationship

You might be confused to hear the word Rhino in a course about Grasshopper. But Grasshopper cannot exist alone, it only works with Rhino. So, it’s important to understand both programs and how they interact.

Rhino is a geometry modelling tool with a command line interface. Grasshopper is a plugin that sits inside Rhino and uses all of Rhino’s geometry and data to do its processing.

This means that Rhino is the backbone of Grasshopper. It provides the data, structure and visuals for Grasshopper to work on. Part of what makes learning Grasshopper difficult is the need to learn the interface of two programs.

To help with that, you should only think of Rhino as a place to store and visualise data. As we gain more Grasshopper experience and understanding, the relationship between these two programs should become clearer.

The Grasshopper Interface

To get to Grasshopper from Rhino, type “grasshopper” in the command line or click the Green ball icon on the “Standard” toolbar.

You should then see Grasshopper load up along with a blank Grasshopper canvas.

In a nutshell, Grasshopper is just a fancy drag-and-drop system. You have components that you can drag onto the canvas and connecting them will tell Grasshopper to process them.

Unlike other modellers, you are giving Grasshopper the steps to create the model and not making the steps yourself.

Say, you wanted to create a line in a normal modelling program. You would use your mouse and physically draw the line in the model.

In Grasshopper, instead of drawing the line yourself, you have to give Grasshopper the logical steps to draw the line. Let's look at what this means in Grasshopper.

Getting Components

So, to draw a line, we need some components.

You can find all the available components in the toolbar on top of the canvas. What we need to start drawing a line is a panel component. It's a component that lets us enter any value.

The panel component will be in Prm tab under input category.

Once you found the component, you can drag it onto the canvas.

Once you get more comfortable with components, you will stop using the toolbar and start using the search bar to get your components. It's quicker and less cumbersome. You can do this by either hitting your spacebar or double-clicking on an empty spot on the canvas.

Going back to how to model a line. We also need to create some points as we need two points to form a line. For that, we need the construct point component.

Which can be found in the Vec tab under Point category.

or better yet, use the search bar to get it.

Now, that we know how to get our components, let’s add some points in Grasshopper. I will use that panel component from earlier to enter my coordinates for the points. I'll create a point at the origin (0,0,0) and one more point along the X-axis. Then canvas now looks something like this:

Notice how even though I connected the panels and construct point components, nothing happened in Grasshopper? To see these points we've created, you need to look at Rhino’s viewport.

Visualising data in Rhino

If you turn your attention to Rhino, you should see two red crosses/dots. They are the two points that we created in Grasshopper.

Note: it’s quite helpful to have two monitors, one for Rhino and another for Grasshopper. It saves you from constantly flicking between Rhino and Grasshopper

This tells you that Grasshopper only processes the data, but to visualise the data, you need to use Rhino.

Now, that we can see our points, we can make our line with the Line component.

Note: The grid in Rhino might be blocking the line. Hit F7 on your keyboard to toggle on/off the grid

If you have noticed the steps to create the line need a lot more information than just drawing the line manually in the program. When we created the line, we had to worry about the exact coordinates of the points.

This is because the steps we give Grasshopper rely on logic and maths.

The good news is that because we are giving the steps to Grasshopper, we can make changes to the model and see the update immediately.

And, with just a few components, we have created our very first model in Grasshopper. Albeit a simple one, it's the beginning of your Grasshopper journey.

Today’s Homework

Great job getting through today’s lesson! Learning a new program is never easy, learning two programs is even harder.

I am leaving you with some homework before we meet again in 2 days for our next session.

I want you to make a Rectangle by using the new components that you learnt today: the panel, construct point, and line components.

As you do the homework, just know that it’s okay to struggle and feel frustrated, it’s part of the learning process. Grasshopper and Rhino are sophisticated and powerful programs. Just know that with practice and some time, most of it will feel like second nature.

Good luck with the homework!


Here is Grasshopper’s official tutorials page, I haven’t found them that useful but if you have time, have a browse through them to see more of what Grasshopper is about: