When is AddForce actually applied ?

Questions & Answers
1

So i have the following code to make a rigidbody move:

    void Update()
    {
        inputVector.x = Input.GetAxis("Horizontal") * acceleration * rigidbody.mass * Time.deltaTime;
        inputVector.y = Input.GetAxis("Vertical") * acceleration * rigidbody.mass * Time.deltaTime;

        rigidbody.AddRelativeForce(inputVector.x, 0, inputVector.y);
        horizontalMovement = new Vector2(rigidbody.velocity.x, rigidbody.velocity.z);

        if (horizontalMovement.magnitude > currentMaxSpeed)
        {
            horizontalMovement.Normalize();
            rigidbody.velocity = new Vector3(horizontalMovement.x * currentMaxSpeed, rigidbody.velocity.y, horizontalMovement.y * currentMaxSpeed);
        }
    }

The problem is, that Applyforce doesn’t seem to care that i resett the velocity of the body if it’s going too fast, which would happen if i set acceleration too high. So i wonder, when is it actually applied ?

And more importantly, how do i fix that ? I tried setting the velocity manually, which indeed solved the problem (hence this question). But, well i can’t seem to figure out how i would go about and add my cute little inputVector to the velocity. That’s because my brain has trouble following this whole relative rotation thingy. Meaning that i don’t know how i would convert that worldspace-input to relative-input.

Also: Have patient with me, i’m really bad at math and come from xna, which uses a slightly different coordinatesystem. And i also only did 2D so far, where relative rotation is relatively irrelevant =) (And you also have to write pretty much all physics stuff yourself, so you at least know what’s going on :/)

Edit: I actually figured it out.

        inputVector = rigidbody.transform.forward * Input.GetAxis("Vertical");
        inputVector += rigidbody.transform.right * Input.GetAxis("Horizontal");

        inputVector.Normalize();
        inputVector = inputVector * acceleration * rigidbody.mass * Time.deltaTime;

        rigidbody.velocity += new Vector3(inputVector.x, 0, inputVector.z);
        horizontalMovement = new Vector2(rigidbody.velocity.x, rigidbody.velocity.z);

        if (horizontalMovement.magnitude > currentMaxSpeed)
        {
            horizontalMovement.Normalize();
            rigidbody.velocity = new Vector3(horizontalMovement.x * currentMaxSpeed, rigidbody.velocity.y, horizontalMovement.y * currentMaxSpeed);
        }

Still, the question remains. What’s up with AddForce ? I’d also welcome any comments on the code. Sigh… and all that just because i want the code to correct for wrong input :open_mouth:

2

Hi,

first of all, move everything that works with physics into FixedUpdate. Google difference between Update and FixedUpdate to understand why.

and your calculation is somewhat strange… if you reach currentMaxSpeed, you cut it back to speed=1 because you normalize…

I would do it like this:

// Lets use Vector3 herem so we don't need to switch between V3 and V2:
// I'm using GetAxisRaw, because you normalize anyway, so you don't need the smoothing that GetAxis provides


public float currentMaxSpeed = 10f;
public float acceleration = 0.1f; // how fast do we accelerate or deaccelerate to wanted speed? 0..1

Vector3 input = new Vector3(Input.GetAxisRaw("Horizontal"), 0, Input.GetAxis("Vertical")).normalized;

Vector3 newV = Vector3.Lerp(rigidbody.velocity, input*currentMaxSpeed, acceleration);

rigidbody.velocity = newV;