Making a vector3 z coord have a zero on reflect?

Question

Right so before you laugh at my silly question lets get the laughs out of your system with a joke.... why did the chicken fall through the world?.... cause he wasn't rigid body enough HAHAHA..... alright in all seriousness i found this little code and want to implement it so that x,y are always reflected but not the z. so when it hits an angle of an edge i will notice through debugged that it gains a z and will fly off in the distance.

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class Ball_Behaviour : MonoBehaviour 
 {
     [SerializeField]
     private Vector3 initialVelocity;
 
     [SerializeField]
     private float minVelocity = 10f;
 
     private Vector3 lastFrameVelocity;
 
     private Rigidbody rb;
 
     void OnEnable()
     {
         rb = GetComponent<Rigidbody> ();
         rb.velocity = initialVelocity;
     }
     
     // Update is called once per frame
     void Update () 
     {
         lastFrameVelocity = rb.velocity;
     }
 
     void OnCollisionEnter(Collision col)
     {
         Bounce (col.contacts [0].normal);
     }
 
     private void Bounce(Vector3 collisionNormal)
     {
         var speed = lastFrameVelocity.magnitude;
         var direction = Vector3.Reflect (lastFrameVelocity.normalized, collisionNormal);
 
         Debug.Log ("Out Direction:" + direction);
         rb.velocity = direction * Mathf.Max (speed, minVelocity);
     }
 }

so basically what i want is a way that if the object hits a corner and wants to go in z i can set it to 0 or make it so that the z isn't possible to start with.... i hope this makes sense for what i want.

Thank you for your time MajorSmurf

Answer 1

Best Answer

Answer by ModLunar · Jul 31, 2018 at 02:36 AM

Ahh okay I think I know what you mean now (for future Google people, see the comments too, I asked for clarification)

Without looking too much into it, I'd probably force it along the xy-plane by changing it to
Mathf.Max (speed, minVelocity) * Vector3.Scale(new Vector3(1, 1, 0), direction).normalized;
instead of
direction * Mathf.Max (speed, minVelocity); on line 40 (at the very end)

Vector3.Scale(...) will take 2 Vector3s and multiply their corresponding x, y, and z compenents together, so you can multiply by 1 in the x and y to keep whatever the velocity was in the xy axes, but then multiply by 0 in the z to have the velocity there be zero.

For example, Vector3.Scale(new Vector3(1, 1, 0), new Vector3(10, 7, 4)) would give you back an expression equal to new Vector3(10, 7, 0)

By getting rid of the z-component, you need to re-normalize the vector cause it lost its length of 1. Then once it has a length of 1 again, you can multiply by the speed to give you the right size velocity vector.

And a side note, if you're working with Rigidbodies, you may want to check in the inspector, under "Constraints", turn on "Freeze Position Z" so that it can't move (from forces) in the z-axis. I'd still make that change though in the script if you want them to not "lose out on speed" if their direction was not going to be exactly xy-plane parallel.

Add comment · Show 3 · Share

MajorSmurf · Jul 31, 2018 at 01:51 PM 0

Share

that's perfect thank you ill give it a try later today. see i was thinking about freezing the rigidbody but i thought that would affect the bounce but maybe i took a easy to fix problem and made it difficult for no reason xD.

thanks for you help :3.

MajorSmurf MajorSmurf · Jul 31, 2018 at 02:34 PM 0

Share

Ok the code worked perfectly apart from the balls beco$$anonymous$$g a little floaty? I'm not sure that's the word to describe it but I'm guessing its just an easy solution of adjusting the numbers. But this works perfectly thank you again and I'm not gonna lie you must likely will see again soon xD.

oh one last question the vector.scale multiples two vectors together I'm assu$$anonymous$$g it has no problem with negatives, decimals and if i was to take a vector 2 and vector 3 and use this would it have a problem with that or does have to be 2 vector3s?

ModLunar MajorSmurf · Jul 31, 2018 at 09:17 PM 0

Share

Of course, haha I'm glad to help! :)

Ah, they have to have the same number of dimensions. So it can't work on a Vector2 and a Vector3, but there is Vector2.Scale(...) as well! You can cast Vector3s to Vector2s if you need to.

Making a vector3 z coord have a zero on reflect?

1 Reply

Your answer

Welcome to Unity Answers

Follow this Question

Related Questions