0 Understanding of raycast2D commands

Make sure you're using Physics2D and not Physics. Physics.Raycast will only look for 3d colliders, where Physics2D.Raycast will only look for 2d colliders.

Here's a smaller example.

[code] using System.Collections; using System.Collections.Generic; using UnityEngine;

public class ExampleClass : MonoBehaviour {

 // Update is called once per frame
 void Update () {
     Example();
 }

 public void Example() {
     Vector2 origin = this.transform.position;   // Start of the ray
     Vector2 direction = this.transform.right;   // Ray's direction
     float distance = 2f;                        // How long is the ray?     (optional)
     LayerMask collisionMask = 1;                // What can the ray hit?    (optional)
     RaycastHit2D hit;                           // What did the raycast hit?

     //hit = Physics2D.Raycast(origin, direction); // To infinity
     hit = Physics2D.Raycast(origin, direction, distance, collisionMask);    // Only go the exact distance, and only hit whatever is included in the collisionMask.
     Debug.DrawLine(origin, origin + (direction * distance), Color.green);   // Draws the ray
     if (hit) {
         print(hit.collider.name);   // Print the name of what was hit, if anything was hit.
     }
 }

} [/code]

Here's a little tutorial.

Create some 2D Sprite GameObjects and add BoxCollider2D components.

GameObject > 2D Object > Sprite

Make sure their Sprite property is set to something so you can see it.

Add Component > Physics 2D > Box Collider 2D

Then create another GameObject, position it below one of the sprites, and attach this script.

Run the scene. When you left-click, the script casts a ray from the object's transform.position upwards (according to the object's transform.up). When you right-click, it raycasts into the screen at the mouse position.

Raycast2DTest.cs

 using UnityEngine;
 
 public class Raycast2DTest : MonoBehaviour
 {
     public float maxDistance = 10f; // 10 metres
     public LayerMask hitMask = -1; // -1 means hit all layers
     public float minZDepth = -1000;
     public float maxZDepth = 1000;
     // The raycast will hit Collider2D's with a Z value between minDepth and maxDepth.
 
     private void Update()
     {
         // If left mouse button pressed,
         if (Input.GetMouseButtonDown(0))
         {
             // Raycast upwards from the GameObject.
 
             Vector2 origin = transform.position; // starting point of raycast
             Vector2 direction = transform.up; // direction to raycast from origin
 
             // Specify all possible parameters for Physics2D.Raycast()
             RaycastHit2D hit = Physics2D.Raycast(origin, direction, maxDistance, hitMask, minZDepth, maxZDepth);
 
             // If something was hit,
             if (hit.collider)
             {
                 Debug.Log("Hit: " + hit.collider.name + ", distance: " + hit.distance);
                 // Draw line in Scene view from `origin` to `hit.point` for 3 seconds.
                 Debug.DrawLine(origin, hit.point, Color.red, 3f);
                 // Draw ray in Scene view to represent the `normal` vector for 3 seconds.
                 Debug.DrawRay(hit.point, hit.normal, Color.green, 3f);
             }
             else
             {
                 Debug.Log("Nothing hit.");
             }
         }
 
         // If right mouse button pressed,
         if (Input.GetMouseButtonDown(1))
         {
             // Raycast from where the mouse clicked on the screen.
 
             // Turn mouse screen position to world position.
             Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
 
             // if direction == Vector2.zero, the raycast will be a single point into the screen.
             ray.direction = Vector2.zero;
 
             RaycastHit2D hit = Physics2D.Raycast(ray.origin, ray.direction);
             if (hit.collider)
             {
                 Debug.Log("Hit: " + hit.collider.name);
             }
             else
             {
                 Debug.Log("Nothing hit.");
             }
         }
     }
 }