assignment.md

Create a Basketball Game App in Unity: Part 2

Prerequisites

Unity

The activity requires you to create an app in Unity. If you don't already have Unity installed, visit unity.com/download to download the Unity Hub. This activity can be completed with Unity version 2020.3.20f1 or newer.

Visual Studio

This activity requires you to create code in Visual Studio. Ensure that Visual Studio is downloaded and set as the default editor for Unity. If you're unfamiliar with the steps to set Visual Studio as the default editor, review Set Your Default Script Editor. This activity can be completed with Visual Studio 2019 or newer.

Unit 6 Activity Project

This activity picks up at the conclusion of the Unit 6 activity. If you haven't completed the activity, download and open the Unit 6 Activity Project in Unity.

Instructions

In this activity, you'll create game play functionality for the basketball game.

Create Player Movement

For this prototype, you'll simulate player movement with keyboard input. The left and right arrow keys should move the player in the respective directions.

1. Create a script that'll enable you to move the Player in the corresponding direction of the arrow keys. To create a new script, in the Project window, right click into the Scripts folder and select Create > C# Script. Name the script PlayerControls and double click to compile and open in Visual Studio.

   

2. In Visual Studio, add the following script and save (WILL PROVIDE EXPLANATION LATER):

   using System.Collections;
   using System.Collections.Generic;
   using UnityEngine;
   
   public class PlayerControls : MonoBehaviour
   {
       public float moveSpeed = 5;
   
       // Start is called before the first frame update
       void Start()
       {
   
       }
   
       void Update()
       {
           //Creating a direction vector based on the input axes (X being Horizontal direction, Y being 0 as we do not want the player to move beyond the plane and Z being Vertical direction).
           Vector3 direction = new Vector3(Input.GetAxisRaw("Horizontal"), 0, Input.GetAxisRaw("Vertical"));
           //Change the position transform by the direction vector times the preset movement speed and the time.
           transform.position += direction * moveSpeed * Time.deltaTime;
           //Makes the character look towards the vector's direction.
           transform.LookAt(transform.position + direction);
       }
   }

3. In the Unity editor, add the PlayerControls script as a component to Player. You can do so by dragging the script onto the Player GameObject. You can verify that the script became a component by looking at the Player GameObject in the inspector window.

   

4. Press Play to test the script.

   • Press the right arrow key to move the Player to the right.
   • Press the left arrow key to move the player to the left.
   • Press the up arrow key to move the player forward.
   • Press the back arrow key to move the player back.

   

Create Character Ball Hold

When the game starts, the basketball is placed at a hold position in front of the player. Create a hold position for the player.

1. In the Hierarchy window, select Player. Right-click and select Create Empty. Name the object HoldPos.

   

2. The HoldPos should be placed in front of the Player at about arms height (slightly above the half-way mark of Player). Modify the HoldPos Transform Position to 0, 0.2, 1.2. This positions the HoldPos in front of the player and a short direction upwards.

   

3. Using code, place the basketball at the HoldPos for the start of the game. In Visual Studio, add a GameObject variable for the basketball and a Transform variable for the position of HoldPos to the PlayerControls script:

   public GameObject basketball;
   public Transform holdPos;

   The basketball variable holds the basketball GameObject. The HoldPos variable holds the position of the HoldPos GameObject. You can use these two variables together to reposition the basketball.

4. In the Start() method, add the following to position the basketball at the position of holdPos for the start of the game:

   void Start()
   {
       basketball.transform.position = holdPos.position;
   }

5. In the Unity editor, expand the Player Controls script component on the Player. Drag the basketball GameObject into the Basketball field. Also, drag the HoldPos GameObject into the Hold Pos field.

   

6. Press Play to test the script. The basketball be positioned at the HoldPos when the scene starts.

Hold Ball Overhead

Before the player can shoot the ball, they must hold the ball over their head. This ensures that the ball is held at an optimal height for the shooting arc that you'll later create. Since the player can only hold the ball if the ball is not already shooting towards the hoop, you'll need to create boolean logic to account for the status of the ball. Create an overhead position for the ball and a conditional statement that checks whether the ball is being held by the player. If the player is holding the ball, use the space bar key to hold the ball overhead.

1. In the Hierarchy window, select Player. Right-click and select Create Empty. Name the object OverheadPos.

   

2. The OverheadPos should be placed in front of the Player above their head. Modify the OverheadPos Transform Position to 0, 0.5, 1.2. This positions the OverheadPos in front of the player and slightly above their head.

   

3. In the PlayerControls script, create a Transform variable for the position of OverheadPos.

   public Transform overheadPos;

4. Next, create two boolean (true/false) variables that'll define whether the ball is in the Player hand's or flying towards the hoop.

   //Our game will start with the ball in the character's hand, thus the assigned value is true.
   private bool isBallInHands = true;
   private bool isBallFlying = false;

   At the start of the game, the basketball is in the Player hands. Therefore, at the start of the game isBallInHands is true and isBallFlying is false.

5. Next, add a conditional statement that checks whether the ball is being held by the Player. If the ball is in their possession, then pressing the space bar on the keyboard will raise the ball to the OverheadPos. Add the following conditional statement below in the Update() method after the Player's movement controls:

   if (isBallInHands)
   {
       //If it is, we will define the space key as the key to hold the ball over the character's head.
       if (Input.GetKey(KeyCode.Space))
       {
           basketball.transform.position = overheadPos.position;
       }
       else
       {
           basketball.transform.position = holdPos.position;
       }
   }

6. In the Unity editor, expand the Player Controls script component on the Player. Drag the HoldPos GameObject into the Overhead Pos field.

   

7. Press Play to test the script. Press the space bar key to raise the basketball.

Shoot the Ball

Once the ball is placed above the player's head, the player can shoot the ball. The player aims for a target (which is essentially the basketball hoop. The ball is considered to be shot once the space bar key is lifted. Create a GameObject for the target positon and a conditional statement that checks whether the space bar key has been lifted. If the space bar key is lifted, then shoot the ball.

1. In the Hierarchy window, select basketball-hoop. Right-click and select Create Empty. Name the object TargetPos.

   

2. The TargetPos should be placed in front of the hoop. Modify the TargetPos Transform Position to -0.4, 12, -2.4. This positions the TargetPos at the hoop of basketball-hoop.

   

3. In the PlayerControls script, create a Transform variable for the TargetPos and a float variable for the length of time that the basketball is in the air.

   public Transform targetPos;
   private float T = 0;

4. Within the if (isBallInHands) statement modify the statement to include the transform.LookAt() method:

   if (isBallInHands)
   {
       //If it is, we will define the space key as the key to hold the ball over the character's head.
       if (Input.GetKey(KeyCode.Space))
       {
           basketball.transform.position = overheadPos.position;
           transform.LookAt(targetPos.parent.position);
       }
       else
       {
           basketball.transform.position = holdPos.position;
       }
   }

   The transform.LookAt() method faces the Player in the direction of the basketball-hoop.

5. Add another conditional statement within the if (isBallInHands) statement that checks whether the space bar key has been lifted:

   if (Input.GetKeyUp(KeyCode.Space))
   {
       //For the ball to be shot, it must leave the character hands, so we make the boolean variable false.
       isBallInHands = false;
       //To begin shooting, we change the boolean flying to true (as the ball starts flying from the hands)
       isBallFlying = true;
       //And restart the time (so that the new series of events can be easily written)
       T = 0;
   }

6. The next step is to add what happens once the basketball is shot. Once the basketball is shot, the program uses two vector points (TargetPoint and OverHeadPos) to determine the direction of the basketball. A new vector is created from these vectors and the basketball position is changed accordingly. Add the following conditional statement after the if (isBallInHands) statement.

   if (isBallFlying)
   {
       //Time variable is assigned a new value based on the time the event starts
       T += Time.deltaTime;
       //duration of travel
       float duration = 0.5f;
       //This variable allows for the interpolation to be accurate, as we want a set duration for the shooting.
       float t01 = T / duration;  
     
       Vector3 point_A = overheadPos.position;
       Vector3 point_B = targetPos.position;
       //Lerp is the linear interpolation function, will result in a new vector that will represent the trajectory from A to B.
       Vector3 pos = Vector3.Lerp(point_A, point_B, t01);
   }

7. To shoot the basketball in a realistic way, you can create an arc and add it to the basketball position once shot. Add the following in the if (isBallFlying) statement:

   //Arc created using sine function
   Vector3 arc = Vector3.up * 5 * Mathf.Sin(t01 * 3.14f);
   //Moves the ball in an arc function 
   basketball.transform.position = pos + arc;

8. In the Unity editor, expand the Player Controls script component on the Player. Drag the TargetPos GameObject into the Target Pos field. Also, drag the HoldPos GameObject into the Hold Pos field.

   

9. Press Play to test the script. Press and release the space bar key to shoot the ball. Notice that although the basketball shoots in an arc towards the TargetPos, the basketball continuously bounces up and down in the air. You can add physics to resolve this problem.

Add Physics to the Basketball

Physics is necessary for the ball to move as intended once it's shot into the air. Usually, when a basketball is shot, the ball also rolls on the ground. Adding a Rigidbody to the basketball enables the physics that's needed for these actions.

1. In the Hierarchy, select the basketball and add a Rigidbody component.

   

2. You'll manipulate the physics for the object within the PlayerControls script. Therefore check the Is Kinematic box. If Is Kinematic is enabled, the object is not driven by the physics engine, and can only be manipulated by it's Transform.

   

3. In the PlayerControls script, add the following at the end of the if (isBallFlying) statement:

   if (t01 >= 1)
   {
       isBallFlying = false;
       basketball.GetComponent<Rigidbody>().isKinematic = false;
   }

Add a Collider to the Basketball

Currently, after the basketball is shot, the ball falls through the Court. A collider creates an invisible mesh around the ball that'll enable the ball to instead collide with the Court. Add a Sphere collider to the Basketball.

1. In the Hierarchy, select the basketball and add a Sphere Collider component.

   

2. Now that basketball has a collider, the collider needs to be resized to fit the shape of the ball. In the Sphere Collider properties, select Edit Collider and resize the collider.

   

3. Press Play to test the changes. After the basketball is shot, the ball falls to the ground and stays in place.

Pick Up the Ball

After the player takes a shot, the basketball falls to the court and stays in place. The player should instead receive the ball back to take another shot. Using code, create logic for the player to get the basketball after taking a shot.

1. In the Player Controls script, add the following after the if (isBallFlying) statement and outside of the Update() method:

   //when the collision trigger happens, this method is executed.
   private void OnTriggerEnter(Collider other)
   {
   //Conditional: If the ball isn't flying or has not been picked up yet, pick up the ball and activate its Rigidbody component's kinematics.
   if (!isBallInHands && !isBallFlying)
   {
       isBallInHands = true;
       basketball.GetComponent<Rigidbody>().isKinematic = true;
   }

2. In the Hierarchy, select the Player. Now in the Inspector, go to the object's Box Collider and click on the isTrigger box.

   

3. Press Play to try out the game. After the basketball is shot, the basketball returns to the HoldPos and is ready for another shot. As the player moves around the court, the player's orientation changes to face the basketball-hoop before taking a shot.

   

Solution

To view the project sample for this activity, import the Unit 7 Assignment Unity package that's within the XR Development for Beginners repository.

How to Import a Package into Unity

1. In top navigation menu, select Assets > Import Package > Custom Package.
2. In the Import Unity Package window, select All then Import.
3. Once the package is imported, open the Unit-7 scene.