Why does multiplying a Vector2 by 100 cause rounding errors?

Questions & Answers
1

In my 2D project I have a character launching a projectile at a target. I want the projectile to continue until it hits a target or leaves the ‘game space’ and I delete it. Here is my function for moving the projectile when it gets spawned:

private Vector2 targetPosition;
private Vector2 mouseLocation;
public float moveSpeed = 5;

void Start()
    {
        mouseLocation = Input.mousePosition;
        targetPosition = Camera.main.ScreenToWorldPoint(mouseLocation);
    }

    // Update is called once per frame
    void Update()
    {
        transform.position = Vector2.MoveTowards(transform.position, targetPosition, moveSpeed * Time.deltaTime);
    }

Currently the object stops when it reaches the targetPosition, but I want it to continue on it’s path indefinitely (until I destroy it later).

I’ve tried just scaling the targetPosition vector by multiplying it by 100f but I get rounding errors like so:

void Start()
    {
        mouseLocation = Input.mousePosition;
        targetPosition = Camera.main.ScreenToWorldPoint(mouseLocation);
        Debug.Log("targetPosition: " + targetPosition.ToString("F3"));

        targetPosition *= 100f;
        Debug.Log("new targetPosition: " + targetPosition.ToString("F3"));
    }

output:

targetPosition: (-3.485, -3.115)
new targetPosition: (-348.462, -311.539)

targetPosition: (3.254, -1.408)
new targetPosition: (325.385, -140.769)

targetPosition: (-0.469, 1.300)
new targetPosition: (-46.923, 130.000)

Am I approaching this wrong? Why is multiplying the vector giving rounding errors? Is there another way to get a vector that is a straight line between the spawn location and mouse location, but extended by a factor of 100?

2

Hi,

I think the issue is that Debug.log rounds vectors to one decimal point.

Try the overload option to show 3 decimal points and you should understand what is happening:

 vector = new Vector3(1.234f, 5.678f, 9.012f);
 Debug.Log(vector.ToString());
 // unity shows (1.2, 5.7, 9.0)

 // but we can show this using format - 3 numbers after the decimal point
 Debug.Log(vector.ToString("F3"));
 // (1.234, 5.678, 9.012)