Advanced Arrays
Time 3.6 hrs

Difficulty Intermediate
Prerequisites Data Structures & Graphs
Departments Science
Authors Sandra Kuipers
Groupings Individual
Minimum Year Group None

Blurb

Advanced Arrays

License

This work is shared under the following license: Creative Commons BY-SA-NC

Outline

Learner Outcomes
Students will:
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Competency Focus
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Interdisciplinary Connections
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Reflection
What was successful? What needs changing? Alternative Assessments and Lesson Ideas? What other Differentiation Ideas/Plans could be used?
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5 mins
Arrays
Getting Started
  • As code gets more complex, arrays are essential.
  • They allow us to manage a huge number of objects by using loops and indexes.
  • Let's start with a quick recap of Arrays in Unity:

From Unity Learn scripting tutorials.

5 mins
C# Built-in Arrays
Theory
  • C# has a lot of advanced ways of handling arrays.
  • The example above looks at built-in arrays.
  • Built-in arrays are the fastest and most efficient type of array.
    • Built-in arrays are created with a value type and square brackets, eg: int[].
    • Their size must be declared when the array is created, and cannot be changed.
    • This is what makes them fast: because they always use the same block of a computer's memory.
    • However, an array that cannot change size is more limited in its uses.
  • Here's an example of declaring and working with a built-in array.
public class ExampleClass : MonoBehaviour
{
    // Exposes an float array in the inspector, which you can edit there.
    public float[] values;
    void Start()
    {
        foreach (float value in values)
        {
            print(value);
        }

        // Since we can't resize builtin arrays
        // we have to recreate the array to resize it
        values = new float[10];

        // assign the second element
        values[1] = 5.0F;
    }
}
10 mins
C# Lists
Theory
  • Lists are another type of array in C#, and these ones come with a lot more features.
    • Lists are resizable as well as searchable, which makes them quite useful.
    • However, these features can come at a performance cost if the list gets really big.
  • Here's an example of declaring a list in C#. Note that the variable type is inside <>.
List<GameObject> = new List<GameObject>();
  • Lists are easy to use. There is a huge list of different operations that you can perform with it. Here are some of the common ones to start with:
    • Add: This adds an object at the end of List.
    • Remove: This removes the first occurrence of a specific object from List.
    • Clear: This removes all elements from List.
    • Contains: This determines whether an element is in List or not. It is very useful to check whether an element is stored in the list.
    • Insert: This inserts an element into List at the specified index.
    • ToArray: This copies the elements of List to a new array.

  • Dictionaries are similar to lists, but instead of an integer for an index, they can use a string, known as the array key.
5 mins
3D Arrays
Examples
  • Arrays can exist in more than one dimension.
  • Technically, they can be as many dimensions as your computer's memory allows, which is a lot!
  • For built-in arrays, we can declare a multi-dimensional array using the following syntax.
public int[,,] myArray = new int[10,10,30];
  • This syntax declares an array which has three dimensions, making it a 3D array.
  • We can access items in a 3D array with a similar syntax.
myArray[0,0,0] = 42;
  • This assigns the first item in each dimension of the array to the value of 42.
  • To iterate over a 3D array, we use a loop that is nested three times:
for (int x = 0; x < myArray.GetLength(0); x++) {
    for (int z = 0; z < myArray.GetLength(1); z++) {
        for (int y = 0; y < myArray.GetLength(2); y++) {
            // Do stuff!
        }
    }
}
  • In the above example, we can get the length of a single dimension in an array with the GetLength() method.
  • This example iterates over x and z first, because in Unity these are the horizontal dimensions. Then it iterates over y, which is the height of the 3D array.
5 mins
Minecraft Arrays
  • What better example of a 3D array is there than a Minecraft world!
  • Each "chunk" of the world in Minecraft is a 3D array of cubes.
  • Every chunk is also part of a bigger 3D array of chunks.

  • The world is created procedurally by determining which parts of the array should be solid blocks, and which should be open air.
  • The procedural scripts also use different types of noise and cellular automata to place caves, trees and other decorations in the world.
  • We'll look at procedural generation a bit more in-depth in a following unit, this unit is just the intro :)
5 mins
Minecraft Math
  • Minecraft uses a 3D array to create a map of cubes. But, it's not a solid block of cubes.
  • The map generator in Minecraft uses procedural generation to decide which parts of the array are cubes, and which are open air.
  • To understand how it works, we need to take a quick look at what pseudorandom numbers are.

  • Perlin noise is a type of pseudorandom number. This means it appears random, however it's deterministic: the number will always be the same for any given input.
  • Perlin noise looks like a 2D waveform. For any given x and y input, it will return a fraction between 0 and 1.

  • These numbers "wobble" and change smoothly between 0 and 1, giving the perlin noise pattern above.
  • So, how does the relate to Minecraft?
    • Well, many games that use procedural generation begin with the humble Perlin Noise function.
    • Behind the scenes of this function is a mathmatical algorithm that generates the value between 0 and 1.
    • Luckily, you don't need to know the math, just the input and output of the function.
    • In Unity, the function is called Mathf.PerlinNoise(x,y)
  • Look at the waveform above. Looks kind of like hills and valleys, right?
  • Well, if you were to use Perlin Noise to generate a 3D map, you could the value it returns to decide if a point in the map should be a cube or open air.
  • Consider the following conditional:
float noise = Mathf.PerlinNoise((float)x/10f, (float)z/10f) * (float)height;
if (y < noise)
{
    // Make a cube
}
  • In this example, the code is getting a perlin noise value and multiplying it by the height of the terrain to create.
  • Instead of a number between 0 and 1, this creates a number between 0 and the max height of the terrain.
  • Then, it's looking at the y value of the cube it's currently drawing.
  • Is this y value less than the noise?
    • If yes, this point is underground, so draw a cube.
    • If no, it doesn't draw a cube, which leaves open air above the ground.
  • Repeat this in a 3D nested for loop and you can begin to generate a whole 3D map!
180 mins
Your Advanced Array
Evidence
  • 2D and 3D arrays are used all the time in game design to hold data.
  • They are used for grids, maps, level design, etc. For example:
    • Many games use a 2D grid for their inventory system that stores items.
    • Minecraft and block-based games use a 3D grid of cubes that can be created or destroyed.
    • Mario and sidescroller games use a 2D grid to design the game level.
  • In this unit, you'll use either a 2D or 3D array to create and manipulate a set of objects.
  • What those objects are and what the grid is used for is up to you!
  • The goal is to create your array procedurally:
    • This means the data doesn't exist before you press play on your game.
    • Instead, in the start() method, you would initialize and create the objects in your array.
    • You could use randomization or a noise function to create the objects.
    • Each object would be saved to your array at a numerical index (x,y for 2D, x,y,z for 3D)
    • Using the numerical index, you can manipulate your objects after they're created.
  • Experiment with your 2D or 3D array to create a scene in Unity that can be both generated and manipulated.
  • Once you're happy with your scene, zip it and upload the Google drive, then submit it as your evidence of learning in this unit.
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