How to calculate an objects velocity to display to user?

2D
1

Hi I have a moving 2D rigidbody and I want to show the objects velocity in m/s or km/h, but I don’t know how to calculate this or even fake it based on solely the objects rigidbody2d.velocity values.

Does anyone have a formula for converting Unity’s 2D movement into real world or close enough velocity values?

2

Unity velocity is in units/s. To convert those units, it solely depends on the scale you created your game in. If you let 1 unity unit = 1 meter for all your objects when you create them, then velocity is meters/s.

For 2D, the default pixels per unit is 100, so if your velocity is 1, that would be 100 pixels/s. How many pixels are in a meter depends on the physical display your game ends up on.

2 Likes
3

I whould just use velocity values fot one game:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class move : MonoBehaviour {

    Rigidbody2D rb;
    public Vector2 dir;
    public float speed;

    void Start () {
        rb = GetComponent <Rigidbody2D> ();
    }

    void Update () {
        dir = rb.velocity;
        speed = dir.magnitude;
                //or sqrMagnitude as not so cpu expensive
    }
}

and then multiplicate it with float correction.

4

For 2D, Unity uses Box2D which uses units of MKS (Meters, Kilograms and Seconds). Distance is in meters and Velocity is in meters/sec but as was stated above, you could easily assume it was kilometers/sec or World Units/sec.

A Rigidbody2D speed is the magnutide of Rigidbody2D.velocity which is in m/s.