How can I get a component of a rigidbodies velocity?-CodePudding

I'm trying to detect the y velocity in my rigidbody in order to determine whether the player can jump or not. For some reason the component I get from rb.velocity[2] does not match what I see when I log rb.velocity in console. Some help understanding how to get that vertical velocity component from the rigidbody would be very helpful.

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

public class Movement : MonoBehaviour
{
    public Rigidbody rb;
    public Vector3 xvector = new Vector3 (1, 0, 0);
    public Vector3 yvector = new Vector3 (0, 1, 0);
    public float strafeforce = 1f ;
    public float jumpforce = 15f;
    
    // Update is called once per frame
    void Update()
    {
        rb = GetComponent<Rigidbody>();
    }
    void FixedUpdate()
    {
        if (Input.GetKey("right") )
        {
            rb.AddForce(strafeforce, 0, 0, ForceMode.Impulse) ; 
        }
        if (Input.GetKey("left") )
        {
            rb.AddForce(-strafeforce, 0, 0, ForceMode.Impulse) ; 
        }
        if (Input.GetKey("up") )
        {
            rb = GetComponent<Rigidbody>();
            if (rb.velocity[2] == 0)
            {
                rb.AddForce(0, jumpforce, 0, ForceMode.Impulse) ;
            }
            Debug.Log(rb.velocity);
            Debug.Log(rb.velocity[2]);
        }
    }
}

So the problem is that the second value from rb.velocity doesn't match the value I get from rb.velocity[2] for some reason.

CodePudding user response：

In C# indexes start from 0. That means that index 2 would actually be the 3rd component of the vector (i.e. the z velocity). If you want the second component you should actually use rb.velocity[1].

However if you want to get a specific component, for example the y velocity, you can instead use rb.velocity.x, rb.velocity.y and rb.velocity.z. This makes the code easier to read, as you can see at a glance which axis you are trying to access.

CodePudding user response：

The difference only exists in the Log due to different ToString implementations.

Unity's default formatting for Vector3.ToString uses F1 which rounds all values to a single decimal

   public string ToString(string format, IFormatProvider formatProvider)
   {
       if (string.IsNullOrEmpty(format))
           format = "F1";
       return UnityString.Format("({0}, {1}, {2})", x.ToString(format, formatProvider), y.ToString(format, formatProvider), z.ToString(format, formatProvider));
   }

This is not the case for the default float.ToString.

Id you want to be sure they match in the log use e.g.

Debug.Log(rb.velocity.ToString("G9"));
Debug.Log(rb.velocity[2].ToString("G9"));

or actually simply

Debug.Log(rb.velocity.z.ToString("G9"));