2.D Platformer: Double Jump!

Today, I implemented the ability to double jump!

Objective

We want to jump when pressing the space key.

Setup

I want the player to jump with out the use of a rigidbody. So I need to create the logic for gravity as well.

With the character controller script in use from Unity, I can use it’s “isGrounded” property to check if the player is touching the ground or not.

Scripting

In the player script, I added some variables.

[SerializeField] private float _gravity = 1.0f;
[SerializeField] private float _jumpHeight = 8f;
[SerializeField] private bool _canDoubleJump = false;
private float _yVelocity;

I want to store the value of the gravity, so when the player jumps, I can have its y position imitate fall.

I also need a jump height, or jump speed, to give the player its height when jumping.

Also, a bool is needed to control the double jump since I don’t want the player to jump infinitely.

And finally, the Y velocity variable will store the value of the sum:

_yVelocity += _jumpHeight;

After a jump, it will also subtract from gravity, making the player fall to the ground.

_yVelocity -= _gravity;

With the fields set, in the Update() function, I want to check if the player is grounded. If the player is grounded, then we need to check if the jump key has been pressed.

if (_controller.isGrounded)
{
    if (Input.GetKeyDown(KeyCode.Space))
    {
        _yVelocity = _jumpHeight;
        _canDoubleJump = true;
    }
}
else
{
    if (Input.GetKeyDown(KeyCode.Space))
    {
        if (_canDoubleJump)
        {
            _yVelocity += _jumpHeight;
        }
        
        _canDoubleJump = false;  
    }

    _yVelocity -= _gravity;
}

velocity.y = _yVelocity;

If the jump key has been pressed, we want to store the jump height to the Y velocity variable and set the bool “can double jump” to true.

Else, if the player is not grounded, and if the jump key is pressed, I want to check if the player can double jump.

If the player can double jump, we want to add the Y velocity with the jump height and set the “can double jump” bool to false.

I then need to subtract the Y velocity to gravity and store it into y velocity so I can finally apply the data to the player’s vector3 Y position.

Conclusion

I can now jump and fall through simple logic! Since I am following a course, we are not using a rigidbody to add gravity which would help in that regard instead of coming up with our own gravity system.

That is all for today. Thank you for your time!

Gabriel