Raycast Reflection 2D

Question

Hello, I am working on a 2D game in which I would like to add lasers. I did it and it works very well. But now I would like the laser to be reflected on an inclined object to take another direction but I can not do it. Help !!! xD

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class Laser : MonoBehaviour
 {
     private LineRenderer lineRenderer;
     public Transform laserHit;
 
     public Color startColor;
     public Color endColor;
     
     public float coolDown;
     public float time;
     private float timeInitiale;
 
     private void Start() 
     {
         lineRenderer = GetComponent<LineRenderer>();
         lineRenderer.enabled = true;
         lineRenderer.useWorldSpace = true;
 
         lineRenderer.material = new Material(Shader.Find("Sprites/Default"));
         lineRenderer.SetColors(startColor, endColor);
 
         timeInitiale = time;
         time = time + coolDown;
     }
 
     private void Update() 
     {
         RaycastHit2D hit = Physics2D.Raycast(transform.position, transform.up);
         Debug.DrawLine(transform.position, hit.point);
         laserHit.position = hit.point;
         lineRenderer.SetPosition(0, transform.position);
         lineRenderer.SetPosition(1, laserHit.position);
         if(hit)
         {
             PlayerMovement player = hit.transform.GetComponent<PlayerMovement>();
             if (player != null && lineRenderer.enabled == true)
             {
                 player.KillPlayer();
             }
         }
 
         time -= Time.fixedDeltaTime;
 
         if (time <= 0)
         {
             time = timeInitiale + coolDown;
             StartCoroutine(CoolDown());
         }
 
     }
 
     IEnumerator CoolDown()
     {
         lineRenderer.enabled = false;
         yield return new WaitForSeconds(coolDown);
         lineRenderer.enabled = true;
     }
 
 }

Answer 1

I'll help with the math / rotations then let you handle the incorporation. :-)

So a deflected ray (B) will depend on the ray itself (A) and normal of whatever surface it hits (N). If you know both of those values, then you can find a rotation such that A gets rotated to become N. Conveniently, we can apply that same rotation to N to get our B.

Unity makes this pretty straightforward with how it defines quaternion multiplication on vectors:

 public class RayPointer : MonoBehaviour
 {
     // Update is called once per frame
     void Update()
     {
         // Camera is straight for this example, so this is simple
         var mouse = Camera.main.ScreenToWorldPoint(Input.mousePosition);
         var delta = mouse - this.transform.position;
         var ray = new Ray2D(this.transform.position, delta);
 
         Debug.DrawLine(ray.origin, mouse, Color.red, 0f);
 
         var hit = Physics2D.Raycast(ray.origin, ray.direction);
         if (hit)
         {  
             // Get a rotation to go from our ray direction (negative, so coming from the wall),
             // to the normal of whatever surface we hit.
             var deflectRotation = Quaternion.FromToRotation(-ray.direction, hit.normal);
 
             // We then take that rotation and apply it to the same normal vector to basically
             // mirror that angle difference.
             var deflectDirection = deflectRotation * hit.normal;
 
             Debug.DrawRay(hit.point, deflectDirection, Color.magenta, 0f);
         }
     }
 }

I added that to the red cube in a scene and pointing my mouse at a large 2D wall nearby, which gives something like:

alt text

Raycast Reflection 2D

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