Making a Rainbow in ScriptCraft – Part 1


I decided for my first ScriptCraft project I would try to create a rainbow. There were two reasons for choosing this:

  • I thought it’d look nice
  • It would need a bit of maths, so it’s something you couldn’t easily build by-hand

I was a bit disheartened when I found that the creator of ScriptCraft, Walter Higgins, had included a rainbow as a standard function in ScriptCraft, but I persisted regardless and I’m glad I did.

There are, I think, three things that make this script interesting:

  • It’s got some useful maths in it
  • It’s got an array variable
  • It’s got a second function

So, I’ll have a quick chat about each of these, but because it’s fundamental to the rest. This post is all about the maths.

I can just about hear the groans now, but I promise, this is crazy useful and really not that hard.

Useful Maths – Calculating the Area of a Rectangle or Square

The area of a rectangle or square is just the width multiplied by the height. Take a look at the two shapes below. The rectangle is 2 high and 5 wide and contains 2 x 5 = 10 squares. It’s area is 10. The square is 5 high and 5 wide and it’s area is 5 x 5 = 25.


Count the little squares if in any doubt.

Useful Maths – Squares and Square Roots

In a square, width and height are the same so the square’s area is always the same number multiplied by itself. Above it was 5 x 5 = 25.

A number squared is simply the number multiplied by itself. The name makes sense when you see that it relates to the area of a square, as above.

Two squared is 2 x 2 = 4. Three squared is 3 x 3 = 9. A square is often written as the number with a superscript 2 after it. You can see that here:


A square root is the reverse of a square. If 2 x 2 = 4, then the square root of 4 is 2. In the same way, the square root of 9 is 3. Every positive number has a square root, but most aren’t easy to guess like the two I’ve just shown. The square root of 2 is 1.414! A calculator or your computer program can always figure them out though. A square root is normally written as shown here:


Useful Maths – Measuring Distance in 2D and 3D

Now that we know about squares and square roots, we can talk about calculating the distance between two points in 2D and 3D. This is something programmers need to do all the time. The technique that’s used is known as Pythagoras’ Theorem and it’s been round since ancient times.

The person who invented it (probably not Pythagoras, even though his name’s on it now) noticed that there was something interesting about triangles which have right-angles in them (a perfectly square corner). They noticed that if you squared the length of the two shorter sides and added them together that that was the same as the square of the length of the longest side. Notice that the longest side is always the one which is directly across from the right angle. This diagram shows everything I’ve just said visually, showing the squared side lengths as physical squares:


If you’re in doubt, all the little squares are exactly the same size, you can count them to make sure they’re the same.

You might not see it, but we now have everything we need to calculate distances in 2D. Consider two points, shown in red below, which are x units apart horizontally and y units apart vertically:


It’s a right-angle triangle! This means that we know that the distance is related to the length of x and y like this:


but we don’t want distance squared, we only want distance so we can reverse the squaring with a square root which gives:


This is really easily extended to 3D too. If the points are at different Z positions and z is the difference between them in that direction the distance is:


Which is almost exactly the same, but has the z bit added.

In JavaScript – Measuring Distance in 2D and 3D

So, what does this look like in JavaScript? A little different, but easy to understand.

JavaScript doesn’t have a short way to write “squared” so we just multiply the variable by itself to get the squared value.

When it comes to square roots, the built-in Math object has a function for calculating square roots called “sqrt”.

Lets see how this looks together:

var x = 4;
var y = 3;
var distance = Math.sqrt((x * x) + (y * y));

Hopefully you can relate this to what we’ve shown above. Even if you don’t get it, you can still copy and use this code yourself if you need it.

The extension to 3D is almost identical. You’re probably figured it out, but I’ll show it anyhow for completeness:

var x = 4;
var y = 3;
var z = 5;
var distance = Math.sqrt((x * x) + (y * y) + (z * z));


I’ll probably take one more post to finish this off, which could take a day or two to appear. The script will be attached to the last post, so stay tuned!

Combining ScriptCraft and PrintCraft: Write code to build Minecraft structures and 3D Print them


I have bundled ScriptCraft and PrintCraft so that you can write JavaScript code to create objects in Minecraft and then generate 3D printable models with them.

The PrintCraft server is one created by Paul Harter of, version 1.5.0 for CB 1.6.4. It has Paul’s default world with 36 building plots arranged in a clearing in the jungle.

The ScriptCraft plugin is created by Walter Higgins, available at, version dated 2014-08-23.

How to install:

Just download the zip file from this link and unzip it:

It is a Minecraft server that you run.

How to use:

  • Run the server with Run_windows.bat or the corresponding Linux/Mac files.
  • Make sure you are an admin: in the server window, type op <your_username>
  • In Minecraft, connect to the server by selecting Multiplayer – Direct connect and enter localhost
  • Go to one of the plots and press the button to Claim it.
  • Create an object with ScriptCraft code. For example, try /js stonehouse(), which was written by a member of CoderDojo Athenry.
  • Press the Print button to create a printable version of the object. You’ll get web link where you can download your model.


  • Glass, doors, fences and other objects that are not basic blocks don’t render; you just get voids.
  • Many 3D printers are single-colour, so bear that in mind.
  • If you want to reset your world, copy the one in “BACKUP-world”.

The picture below shows the house created with /js stonehouse(). Follow this link to see its PrintCraft 3D model.


ModderDojo Athenry: Planning for MineVention


The Minecraft fans’ convention, MineVention, will take place on Sunday 7 December in the Radisson Blu Hotel, Galway. Tickets are completely sold out, unfortunately.

The organisers of the convention invited CodderDojo Athenry to participate, particularly as we do Minecraft Modding. We will have a booth beside the 3D printer.

Here is our plan for what we will do at our booth:

  • We will demonstrate Java mods written by our group
  • We will demonstrate structures created by people in our group using ScriptCraft
  • The 3D printer will print out a structure that we created in ScriptCraft, and we will show the structure itself
  • We will also show off any other cool Minecraft-related things our modders have done, e.g. their own YouTube videos, their own command blocks, and any interesting structures they have
  • We will also have information and demos to highlight the range of different things done in CoderDojo Athenry apart from Minecraft modding.

Any members of CoderDojo Athenry who have tickets are welcome to join us for some of the time.

ModderDojo Athenry Topic 6: JavaScript Operators and ScriptCraftJS Drone Functions

Our mods:

Download them here:


Operators in any programming language are used when you want to calculate something new: they operate on values. variables, or expressions to produce a new value.

Since ScriptCraftJS is built on the JavaScript langauge, it uses standard JavaScript operators. As it happens, many other programming languages (including C, C++ and Java) use the same operators or very similar ones.

JavaScript Operators

Drone Functions:

As we have seen before, in ScriptCraft you use a drone to do your building for you. The drone has functions that are part of it.

Here are some of the main drone functions that are useful when building your mods:

ScriptCraft Drone Functions

You can find lots more about these and other functions in the ScriptCraft API Reference:

ModderDojo Topic 5: Moving from Scratch to JavaScript


Reminder: JavaScript is a well-established programming language, mainly used in web development. ScriptCraft is a Minecraft mod that allows you to write JavaScript code for building structures in Minecraft and writing new Minecraft mods. (So it’s a mod for creating other mods.)

Steps 1 and 2: Try out ScriptCraft commands and write simple mods

Please look back to last week’s notes for now to do this:

Step 3: Comparing JavaScript to Scratch

Some people criticise Scratch as being “childish”, but I don’t agree. While it is designed so that even 8 year olds can use it, it is still has all of the key features of ‘adult’ programming languages, as listed in the image at the top of this post.

(Technically, any programming language with variables, decision and loops is Turing Complete.)

This means that, if you already know how to write a Scratch programs that use these features, you will be able to apply that knowledge to any other language, such as JavaScript. The syntax of JavaScript is different, but it uses the same computational thinking.





  • Even though they have basic ideas in common, every programming language has its own specific commands that relate to its purpose: Scratch is focused on 2D games and animations, while ScriptCraft is focused on operating inside Minecraft, and JavaScript generally is used for interactive websites.
  • the echo command that features in these slides is not a standard JavaScript command, it is just used in ScriptCraft to display things on your screen in Minecraft.  Everything else is standard JavaScript.

Topic 4: Planning and Building a Complex Structure Mod in Minecraft

PyrimidInside This week we have one main goal: build a substantial mod in ScriptCraft that, when you run it, will create an impressive-looking structure! This will include:

You might find it helpful to work in pairs on designing and coding your mods. During the session, I will ask people to load their mods onto my computer, demo them to the group, and explain how their code works. To get things started, at the top and bottom of this post are pictures of mods created by Ruaidhri and Luke. We will take a look at how they work.


Practical notes:

  • During development and testing, you can end up with lots of incomplete structures that slow down your CraftBukkit server. A simple fix is to delete your world:
    • Stop your CraftBukkit server
    • Open the CraftBukkit folder on your computer: in it you will see folders called world and possibly world_nether and world_the_end delete them all
    • While you are at it, edit in the CraftBukkit folder to make your new world superflat, write level-type=flat and you could also change other properties such as spawn-monsters=false
    • Restart your CraftBukkit folder to create a new, empty world
    • Re-run your scripts to recreate structures that you want
  • Read the ScriptCraftJS API reference to see what commands you can use for your structures:

Topic 3: Creating our First ScriptCraft Mods


(Notes updated September 2015.)

Previous Topic: Connecting to Each Other’s Servers.

Our First Mod: sayhi.js

I’ll show you how to write a very simple one, sayhi.js, and then a more complex one, scraper.js. After that, it’s up to you to figure out what you can do!

In the Canarymod folder, find the folder scriptcraft / plugins, then make a new folder with your name (or any unique folder name).

Using Notepad++, type in the code shown below and save it in a file called sayhi.js. Here are explanations of what everything means:


Try it out in Minecraft and see if it works!

NOTE: Every time you create a new ScriptCraft program or edit one, you have to type /js refresh() in Minecraft to update your changes. If no commands run, make sure you are opped. (In the Canarymod window, type op <your_mincraft_name>).

To run it, type /js sayhi() in Minecraft.

A More Complex Mod: scraper.js

This makes the skyscraper shown above. We will figure out together how it works!


Topic 2: Connecting to Each Other’s Servers


(Notes updated September 2015.)

Note: This continues what we started in Topic 1: Getting Started with ScriptCraft and JavaScript.

Next step: Creating our first Scriptcraft mods.

Previously, we installed a Canarymod server and inside it we installed ScriptCraft, a mod that will allow us to build structures in MineCraft by writing JavaScript code.

Canarymod is a Minecraft Server. Therefore, the instructions we followed to connect to it were:

  • Start MineCraft, making sure it’s the same version (1.8 in our case)
  • Choose Multiplayer, then Direct Connect and enter localhost as the server address
  • If this works, in your CraftBukkit window you’ll see a message that you connected.

Here, localhost is actually means “the address of this local computer”.

But you can also connect to a friend’s computer, if you are all on the same network and you can find out their address. (If you are on different networks, things get a bit more complex: you will have to search online about how to set up port forwarding on your router, and you will probably also need a free Dynamic DNS service.)

On a local network, to find your IP address, open a command window. (In Windows, run or search for cmd.) In the command window, enter the command ipconfig and read through to find an entry like this:

Wireless LAN adapter Wi-Fi:
    Connection-specific DNS Suffix . :
    Link-local IPv6 Address . . . . . : fe21:9ba2:9db6:13e9%4
    IPv4 Address. . . . . . . . . . . :
    Subnet Mask . . . . . . . . . . . :
    Default Gateway . . . . . . . . . :

The IPv4 address is what you need. Get a friend to start Minecraft on their computer, then Direct Connect and enter your IP address. They will then be connected to the server on your computer!

This can be handy if you want to work on projects together.

Next step: Creating our first ScriptCraft mods.

ModderDojo Topic 1: Getting Started with ScriptCraft and JavaScript

Slide1Welcome to ModderDojo Athenry!

(Notes updated September 2015. Previously used the CraftBukkit server, now using Canarymod.)

This stream is aimed at older & more experienced ninjas, mainly in secondary school, who:

  • Know how to program in some language (e.g. a blue belt in Scratch)
  • Already use the PC edition of Minecraft
  • Know how to edit file and know your way around your computer’s filesystem
  • Ideally have already installed a mod yourself

Plan for today:

  1. Install a Canarymod server (a Minecraft server that is designed to be better to extend than a standard Minecraft server)
  2. Install ScrptCraft, a Mod for Minecraft (built with Canarymod) that allows you to write programs to build objects in Minecraft
  3. Try out some ScriptCraft commands
  4. Write our first mod or two in ScriptCraft

In future weeks, we’ll figure out more about the JavaScript language, which is a popular programming language that is often used in web programming.

Step 0: Prepare

Before you start, you’ll need a programmer’s editor and a zip program. I recommend:

You’ll also need to run Minecraft and the server on your own laptop or pair up with somebody.

Steps 1 and 2: Install Canarymod Server and ScriptCraft

Instructions here:

I’ll have files pre-downloaded on a USB flash drive to save time.

We’ll edit the properties file to specify a flat world, creative mode, and give the world a name.

Either follow the instructions linked above to install everything from scratch, or these instructions ot use my pre-=built server:

  1. Download the Canarymod/ScriptCraft server (a single zip file) here:
  2. Create a folder, e.g. C:\ScriptCraft
  3. Move the downloaded zip file into the folder and unzip it
  4. Run canarymod.jar to start it
  5. If Java is not installed, you will need to download it from

You should then be ready to try out ScriptCraft.

Step 3: Try out ScriptCraft

Run Canarymod (with ScriptCraft already installed).

Then start Minecraft. Important: you will have to run the Minecraft version that matches your version of Bukkit (e.g. 1.8.8)

Choose to directly connect to a server and enter localhost – if you’re connecting to a friend’s machine, you’ll need to connect to their IP address.

To run ScriptCraft commands, you have to be an op. In Canarymod window, type op <username> to op yourself.

In Minecraft, type /js echo(“hello world”) and check that it displays the message: if so, you have it installed correctly.

Next Steps …