2D Platformer Character 2 / 4 - Jumping

Lets teach our cat how to jump. First, we need to modify PlayerCat.cs script.

using UnityEngine;
 
public class PlayerCat : MonoBehaviour
{
    // How strong force to apply for sidewise movement
    public float movementForce = 15;
 
    // How strong force to apply for jump
    public float jumpForce = 5;
 
    // Where should we check for ground
    public Transform groundCheck;
 
    // Are we standing on the ground?
    private bool grounded;
 
    // References for various components to use later
    private SpriteRenderer sr;
    private Rigidbody2D rb;
    private Animator anim;
 
    // Use this for initialization
    void Start()
    {
        // Find our components
        sr = GetComponent<SpriteRenderer>();
        rb = GetComponent<Rigidbody2D>();
        anim = GetComponent<Animator>();
    }
 
    // Update is called once per frame
    void Update()
    {
        // Lets see if we are standing on something
        grounded = Physics2D.OverlapPoint(groundCheck.position) != null;
 
        // Jump only when we are grounded
        if (Input.GetButtonDown("Jump") && grounded)
        {
            rb.AddForce(Vector2.up * jumpForce, ForceMode2D.Impulse);
        }
 
        // Set Speed parameter to absolute value of our horizontal speed
        anim.SetFloat("Speed", Mathf.Abs(rb.velocity.x));
    }
 
    // FixedUpdate is called every Time.fixedDeltaTime
    void FixedUpdate()
    {
        // Get value of horizontal axis (left/right arrow or a/d keys),
        // returns value in range [-1.0f, 1.0f]
        var h = Input.GetAxis("Horizontal");
 
        // Flip sprite depending on horizontal input
        if (h < 0.0f)
            sr.flipX = true;
        if (h > 0.0f)
            sr.flipX = false;
 
        // Move player according to horizontal axis
        rb.AddForce(Vector2.right * h * movementForce, ForceMode2D.Force);
    }
}

Then, add empty GameObject to the cat, rename it to GroundCheck and place it right below cat's Capsule Collider. Now, select cat GameObject and drag your new GroundCheck into Ground Check property of PlayerCat.cs script. If all went good, you should have a jumpy cat!

Lets make jumps look nicer by adding different animation for when the cat is in the air. Prepare cat_jump bitmap like before, by slicing it and creating animation out of it. This time, make animation only out of 3rd and 4th frames. Like before, you can delete cat_jump_2 GameObject and cat_jump_2 Animator that unity created. Open cat Animator and add another parameter to it of type bool this time and call it 'Grounded'. Also add your new 'cat_jump' animation to it and make two new transitions to it, one from 'cat_idle' state and one from 'cat_walk' state. Set them up like in screenshot below. Just make sure you set parameters for both of them. Add one more transition, from cat_jump to cat_idle this time, so our cat can land. And finally, modify Update method of PlayerCat.cs script to look like this.

 
    // Update is called once per frame
    void Update()
    {
        // Lets see if we are standing on something
        grounded = Physics2D.OverlapPoint(groundCheck.position) != null;
 
        // Jump only when we are grounded (Space key by default)
        if (Input.GetButtonDown("Jump") && grounded)
        {
            rb.AddForce(Vector2.up * jumpForce, ForceMode2D.Impulse);
        }
 
        // Set Speed parameter to absolute value of our horizontal speed
        anim.SetFloat("Speed", Mathf.Abs(rb.velocity.x));
 
        // Set Grounded animator parameter
        anim.SetBool("Grounded", grounded);
    }

Congratulations, you taught our cat how to jump properly :3

Of course we could continue improving our jump by adding animation for beginning of the jump and landing, but its not really necessary and it would complicate cat Animator. If you are curious how much, take a look at one that has them implemented. If you are up for a challenge, you can try to figure out how to implement it all by yourself :3