Rhino Grasshopper: How to start

New to Rhino Grasshopper? Welcome to some basic instructions on how to get started! In short, I’ll tell you …

• What Grasshopper basically is all about
• About Grasshopper’s relation to Rhino3D
• How to start Grasshopper
• How to customize Grasshopper
• How to use Grasshopper
• How to save Grasshopper Files

This is really a quick summary of information you’ll find more thoroughly explained elsewhere, e.g. in Mode Lab’s Grasshopper Primer. For more background sources also check my own article here.

What is Grasshopper? <

Grasshopper is a Rhino3D plugin that allows you to model things that can’t be done in Rhino3D alone. It is a built-in programming tool. In contrast to other built-in programming tools however that demand code scripting (e.g. Python), Grasshopper offers a more designer-friendly, visual, object-style approach for basically the same ends. The basic idea is to plug data inputs into components that produce geometry output. This illustration from the Grasshopper Primer shows the difference:

Other than some marketing lyrics proclaim this does not mean Grasshopper is always easy to use. You still have to think like a programmer when utilizing it – but then, at least you won’t have to struggle with code syntax. For an architect, this makes a hell of a difference.

You want to see more information? Check my article on Grasshopper learning resources.

Grasshopper and Rhino3D <

Grasshopper is a Rhino3D plugin which means you can’t use it standalone. Until short, you had to download and install it yourself but today it comes pre-installed with Rhino3D V6 (WIN) and Rhino3D V5 (MAC).

You need Rhino3D’s viewports to preview Grasshopper’s geometry output – Grasshopper’s canvas itself can only display your component composition:

A Grasshopper definition (that’s what a working set of components is called) has to be saved to stay with you and the world. Other than Rhino3D’s generic files the format is .gh. Theoretically, Grasshopper files are independeant from Rhino3D files. In practice, there are 2 scenarios, though:

When building up definitions in Grasshopper you can either reference Rhino3D geometry or construct everything directly in Grasshopper. When you input Rhino3D points, curves etc. you have to make sure that you always keep 2 files to save your work: The Rhino3D file (.3dm) and the Grasshopper file (.gh). When you develop your geometry in Grasshopper without any reference to existing Rhino3D geometry you may only keep the Grasshopper file.

You want to see more information? Check my article on Grasshopper learning resources.

How to start Grasshopper <

That’s simple: Type grasshopper into Rhino3D’s command prompt. Or click the Grasshopper icon in Rhino3D’s Standard toolbar:

Either way, Grasshopper opens up. If you have more than one screen, pull Grasshopper’s window onto one of them. If you have only one screen, press the Windows key and the Right-Arrow-key so the Grasshopper window fills the right half of your screen. Do the same for your Rhino3D window, but – of course – put that one on the left half of your screen (Windows-Left Arrow). On Mac, you have a similar way to split your screen for two apps.

You want to see more information? Check my article on Grasshopper learning resources.

How to customize Grasshopper <

There’s not much to customize in Grasshopper compared to larger software suites. Let me show you my favorite changes.

First of all, per default Grasshopper components are displayed with their names on it:

Let’s change the Display settings to Icon:

Now it’s easier to identify (or guess) the component’s function:

At the same location, choose Fancy Wires for connection diplay:

This helps you understand the type of data flow between components later on.

If you want to see distinct colors for Grasshopper-induced geometry previews in Rhino3D, choose the according settings under Display – Preview Settings:

Here you may set colors for the unselected and selected geometry:

That’s all, no more things to customize for the moment. You want to see more information? Check my article on Grasshopper learning resources.

How to use Grasshopper <

To use Grasshopper you will place lots of components on your canvas and connect them. The main problem is always to find the right component. You can browse through the icon sets on top of the canvas, pick the right component and drag it onto the canvas, like this Panel component:

Browsing the panels on top of the canvas in order to find an appropriate component is one way. Another way is to double-click on the canvas and type some command you guess would be the right one. Mostly, Grasshopper will make suggestions along your typing that you can choose from:

If you get more than one suggestion (as here for Lines), choose the right one (or take a guess, at least) using the arrow keys and press Enter when done deciding. The component will appear on the canvas.

To get a Number Slider with numbers you wish, just double-click on the canvas and type, e.g. 1<10<20 – a Number Slider will appear with integers ranging from 1 to 20 showing 10 as default. If you type a number like 0.200 the Number Slider will carry real numbers with 0.200 as default. You can always double-click on the left segement of a Number Slider to reset it’s values:

When you have developed some basic routine in Grasshopper you’ll find this is the most fluent way to get a new component onto your canvas.

If you find a component unfit though you can delete it using one of the according keys on your keyboard.

If you need a component you already have on your canvas (and within reach) you can get it via duplication. There are 2 ways of duplicating. STRG-C + STRG-V produces a disconnected copy. ALT-drag produces a connected copy. (Mind you: First drag, then press ALT on the way. If you press ALT before dragging you’ll space up your canvas. This is a feature, not a bug – doing this allows you to create space for new components between existing ones. It’s called the Moses tool.)

You can select components the way you do it in Rhino3D: Draw a selction rectangle from left to right and you will add only components that are completely inside the rectangle. Draw a selection from right to left and you will add all components touched by the rectangle. Of course you may also click-select objects.

You can group selected components (right-click – Group):

And you can name the group:

This grouping feature is a real life-saver, being the only way to not get lost in your component pasta.

Connect component outputs and inputs via mouse-dragging. You can plug wires from various outputs into one input by holding Shift. You can disconnect by right-clicking an input and choose Disconnect… or by pressing CTRL (STRG) and drag the wire from the input back to the output.

Hovering your mouse cursor over anything will produce a display with more or less meaningful information:

To find out which menu a canvas component comes from you just press CTRL (STRG)-ALT and click on the component. Grasshopper will indicate (showing creepy hand-drawn arrows) where this component comes from.

Want to find a certain component in your crowded definition? Just right-click on the canvas and choose Find (or press F3) – type the first letters of your component and Grasshopper will find and mark it.

Last not least: If you like to keep your component array tidy and aligned you may select a subset of them and use the align and distribute buttons that appear. I do this all the time, especially before grouping the whole bunch.

You want to see more information? Check my article on Grasshopper learning resources.

How to save Grasshopper Files <

That’s easy, just choose the Save command from the File menu.

If you want to configure a Grasshopper file the way you like it (with your own preview colors for example) and use it whenever you start a new Grasshopper project you’ll just have to create a template file. First, save your configured file as a normal Grasshopper file but choose a folder that’s suitable for a template file (i.e., not a normal project folder). Then, under File – Preferences – Files you find a slot where you can define a file to be opened as a template. Just search for your recently saved Grasshopper file, and you’re done:

You want to see more information? Check my article on Grasshopper learning resources.

Roundup <

Although brief this should be enough to get you started with this fascinating piece of software. Just to start training you may have a look at my first Grasshopper project tutorial here. Have fun!

© 2018 / Horst Sondermann / All Rights reserved