set ray only when raycast a specific layer

Question

hey! i want to debug a raycast, but only when it hits a specific layer, if it hits somehwere else, do nothing. here is the code so far:

 using UnityEngine;
 using System.Collections;
 
 public class RaytoMouse : MonoBehaviour {
 
     public float distance = 50f;
 
     //replace Update method in your class with this one
     void FixedUpdate () 
     {    
         //if mouse button (left hand side) pressed instantiate a raycast
         if(Input.GetMouseButton(0))
         {
             //create a ray cast and set it to the mouses cursor position in game
             Ray ray = Camera.main.ScreenPointToRay (Input.mousePosition);
             RaycastHit hit;
             if (Physics.Raycast (ray, out hit, distance)) 
             {
                 //draw invisible ray cast/vector
                 Debug.DrawLine (ray.origin, hit.point);
                 //log hit area to the console
                 Debug.Log(hit.point);
                 
             }    
         }    
     }
 }

Answer 1

The ray cast system allows you to specify a layer mask. It's described in detail in the docs:

http://docs.unity3d.com/ScriptReference/Physics.Raycast.html

But they don't show an example.

The simplest way to use it is to make use of the layer mask utility in unity:

 //get the mask to raycast against either the player or enemy layer
 int layer_mask = LayerMask.GetMask("Player", "Enemy");

 //or this would be just player
 //int layer_mask = LayerMask.GetMask("Player");
 
 //or this would be player, enemy or cows!
 //int layer_mask = LayerMask.GetMask("Player","Enemy","Cows");
 
 //do the raycast specifying the mask
 if (Physics.Raycast (ray, out hit, distance, layer_mask))
 {
 
 }

The docs for it are here:

http://docs.unity3d.com/ScriptReference/LayerMask.html

Basically the layer mask is just an integer. For each layer in your game (up to 32), a corresponding 'bit' is set in your mask. The raycast system can use this 32 bit mask to work out what layers you're interested in. Unity's LayerMask utility is a convenient way of constructing these masks so you don't have to think too hard about bits and masks and stuff!

-Chris

set ray only when raycast a specific layer

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