Unity Raycast scripting Tutorial for 3D and 2D

Unity Raycast is a very handy function and can be used for many purposes in game development. The Raycast function is mainly used in FPS games for shooing and for object detection in AI. If you are making games with Unity then Raycast is a function you should master. Raycast can be used for both 2D and 3D games in Unity. In this tutorial, we will see what is Unity Raycast and how you can use them effectively in games.

Basics of Unity Raycast

Syntax

Physics.Raycast(transform.position, transform.TransformDirection(Vector3.forward), out hit, Mathf.Infinity, layerMask)

Parameters in Syntax

1. First parameter is the starting point of the ray.
2. Second parameter is the direction of Ray.
3. Third parameter is the output parameter containing array of hit colliders.
4. Fourth parameter is the length of Ray.
5. Fifth parameter is the layermask, this specifies which layers to include or exclude.

The Physics.Raycast function casts a new ray and returns a Boolean, which is true if the ray hit a game object. Physics.Raycast will work with both the old and new input system. It’s part of the Unity’s physics engine.

What is Raycast in Unity?

Raycast in Unity is like a laser beam from one position to other. In Unity, Raycast uses mathematical variables like position of the object, range etc. to make this possible. You can specify the origin point and the end point of the ray to be cast or you can also cast a ray from the origin point to an infinite distance in a particular direction. You can also ignore objects using the Raycast function.

Thing to know about Raycast in Unity

You need to know about a few components before making a proper Physics.Raycast.

1. RaycastHit – this variable type is used to store the information received from the Raycast.
2. LayerMask- this is used to mask one particular layer you want the ray to interact or ignore.
3. Range – this specifies the range up to which the ray will travel. It is always a better option to specify range as it helps in performance.

Unity Raycasting from Camera

Video Tutorial

Now that you understand how Raycast works in Unity3D. Let’s try it out in a demo scene. We will create two cubes and set them into two different layers. We will try to hit the cube on the back. Here is the video of what we are going to do.

We will skip the basics like how to create a project in Unity3D. I am assuming you already have a project to cast the ray.

Step1: Setting up the scene for Raycast

1. Create a new scene and go to the hierarchy window.
2. Select Create (+)>3D object>cube. Add two cubes to the scene view.
3. We will be casting the ray from the camera so, let’s align the cube one behind the other from the cameras preceptive. You should be able to see only one cube in the game window.

Step2: Creating layers for Unity Raycast

1. Let’s create two layers called enemy and friend.
2. Click layers dropdown on any Gameobject’s inspector view.
3. Select Add layer and enter the required details.
4. Assign the cube in front of camera as friend and the cube on the back as enemy.

Step3: Adding the script

1. Create a new script component for the camera and name it “ForRaycasting”. The camera will be the origin point for the ray.
2. Add the script below. Remember the script name and the class name should be the same.
3. Save and play.

using UnityEngine;
public class ForRaycasting : MonoBehaviour
{
    
    void FixedUpdate()
    {
        int layerMask = 1 << 6;//Since Friend is layer number 6
        layerMask = ~layerMask; //Inverted to ignore layer
        RaycastHit hit;
        if (Physics.Raycast(transform.position, transform.TransformDirection(Vector3.forward), out hit, 10,layerMask))
        {            
            Destroy(hit.collider.gameObject);
        }
        else
        {            
            Debug.Log("Did not Hit");
        }
    }
}

In the above script we are Raycasting to a range of 10 Units in the forward direction. Physics.Raycast returns true if the ray hits a collider or else it will return false. The hit point data will be available in the hit variable for the above script.

The fifth input is the LayerMask. We use this to skip the Friend layer and hit the Enemy Layer. Let’s see another example on how to use LayerMask to ignore a layer in Unity.

If you do not hit anything then try increasing the range of the ray.

Unity Raycast Scenarios and FAQs

Should you use Raycast in Update or Fixed Update?

The reason why fixed update is used in the above script is, Raycast is a physics engine property, all physics related functions must be called inside void FIxedUpdate and not void Update. Also, it will help you to stop Raycasting when you pause your game in Unity3D with timescale.

How to ignore a layer while Raycasting in Unity?

It often comes to a situation where we don’t want the ray to hit everything. For example, implementing friendly fire in an FPS game. You don’t want your fire to hit friends so, you can just add the friendly players to a layer and ignore them from Raycast. To ignore a layer from the Raycast, you just need to add the bit mask of the layer index to your Raycast expression. You need to add the variable shown below and modify the if statement from the above code. You can also check out our detailed article on LayerMask.

The LayerMask variable needs to be inverted to ignore the layer.

int layerMask = 1 << 5;//bit mask for layer number 5
layerMask=~layerMask
//add the 2nd line if you want to ignore layer 5 if not added it will Raycast only to layer 5
if (Physics.Raycast(transform.position, transform.TransformDirection(Vector3.forward), out hit, 10, layerMask))

Raycasting between two points in Unity

You need to tweak the above code a little to cast a ray between two points. I am assuming you are attaching this script to point1 and casting the ray in the specific direction.

if (Physics.Raycast(transform.position, point2.transform.position-transform.position , out hit, 10))
        {            
            Debug.Log("object is at 10 units range");
        }

There are different ways to do this. Alternatively, you can use the Linecast function to cast a line between two points. Linecast() will return true if there are any objects with colliders between the two points. You can use the layer mask to ignore some objects. Also, Linecast() can be used to detect multiple objects in the path of the ray.

if (Physics.Linecast(transform.position, point2.transform.position))
        {
            Debug.Log("colliders found between the two position");
        }

Raycasting from mouse point in Unity

Mouse point is a little bit trickier than other things in Unity. The device screen is 2D and the game world is 3D. So, you need to convert the mouse position from screen point to game world space position. You need to use the camera for this purpose. Go ahead and tag your camera as main camera before proceeding.

Converting mouse position to ray

Ray ray = Camera.Main.ScreenPointToRay(Input.mousePosition);

Cast a ray with the range and hit attribute

if (Physics.Raycast(ray, out hit, 10))
{
    Debug.Log(hit.gameobject);
}

When to use Raycast?

Mostly Raycast is used to find objects in a particular direction or for shooting. But, one thing to be kept in mind while using Raycast is the effect on performance. If you cast multiple rays of infinite length then your game performance is going to suffer. The general practice is to Raycast when some action happens. For example, in a shooting script Raycast is done only when the mouse button is pressed.

You can also use Raycast for collision detection and unlike Unity’s inbuild collision detection, Raycast doesn’t require a Unity Rigidbody component.

Can Raycast hit objects without Colliders?

Raycast requires colliders in order to interact with the game objects. Raycast will detect objects that have trigger colliders too. Any game object without colliders will not trigger a hit. The object hit will be available in Raycast hit.

An important thing to note is Unity Raycast will not detect colliders for which the Raycast origin is inside the collider. This limitation can be overcome using a setting in case of a 2D game.

What is Unity Raycast hit?

Raycast hit contains all details about the object hit by the Raycast. If the Raycast does not hit any object then Raycast hit returns “Null”. You can get the following details about the hit object.

1. Gameobject.
2. Collider attached to the object.
3. Distance of the object from the origin.
4. Transform
5. Rigidbody details

Is Raycasting performance expensive?

Unity Raycast is a very helpful function but needs to be used carefully. Many developers avoid Raycast in order to boost performance. But you need not worry unless you are making a very performance hungry game. Just keep in mind a few things and you should be good.

1. Never forget to provide the range of Raycast.
2. Try to avoid multiple Raycast simultaneously.
3. Use Raycast with a condition like button press inside void Update.
4. Avoid Raycasting against a mesh collider.
5. Use layer mask effectively.

How to use RaycastAll to hit multiple objects?

If you are looking for a list or array of objects hit by a Raycast, then Raycastall is your best option.

 RaycastHit[] hits;
 hits = Physics.RaycastAll(transform.position, transform.forward, 50.0F);
    foreach(Raycasthit i in hits)
    {
       Debug.Log(i.gameobject);
    }

Make the Ray visible in the Unity editor

Raycast is an invisible ray. It’s not visible in both scene and game view. You can use Debug.DrawRay(origin,direction,color) to draw a ray in the Unity editor. But to make it similar to the ray we have cast you need to use the same ray.

Normally to cast a ray, you don’t need to create a ray variable. You can put the Raycast expression in an if statement and it will return true if it hits something. To draw the ray, we will create a ray variable that takes the origin and direction as input. Then we draw a ray with these properties.

using UnityEngine;
public class Raycasting : MonoBehaviour
{
    
    RaycastHit hit;
    void FixedUpdate()
    {
        Ray ray=new Ray(transform.position, transform.TransformDirection(Vector3.forward));
        
        if (Physics.Raycast(ray, out hit, 10))
        {
            
            Debug.Log(hit.collider);
        }
        else
        {
            Debug.DrawRay(ray.origin, ray.direction*10f,Color.red);
            
            Debug.Log("Did not Hit");
        }
    }
}

Length of Debug.DrawRay

Unity3D docs is a little silent in this area. It doesn’t clearly state how to control the length of the ray in Debug.DrawRay. Length of the ray depends on the magnitude of the direction vector. In the above example, we have used a unit vector and multiplied it with the required length. You cannot multiply it with Mathf.Infinity to make it infinite in length. it doesn’t work. You can only Raycast with infinite length but cannot draw a ray. You can use a big number like 100000f to solve the problem.

Debug.DrawRay(ray.origin, ray.direction*10000f,Color.red);

Make the Ray visible in your game

The above section was about making the ray visible in Unity editor but if you build the game the ray won’t be visible in the game. If you want the ray to be visible in your game then you need to use the line renderer. You can set the start and end point as shown in the script below.

using UnityEngine;
public class Raycasting : MonoBehaviour
{
    LineRenderer lin;
    
    RaycastHit hit;
    void Start()
    {
        lin=GetComponent<LineRenderer>();
    }
    void FixedUpdate()
    {
        Ray ray=new  Ray(transform.position,transform.TransformDirection(Vector3.forward));
        
        if (Physics.Raycast(ray, out hit, 10))
        {
            
            Debug.Log(hit.collider);
        }
        else
        {
            lin.SetPosition(0,ray.origin);
            lin.SetPosition(1,ray.direction*10f);
            
            Debug.Log("Did not Hit");
        }
    }

Unity Raycast in 2D

Unity Raycast can be used in 2D games too but a normal Raycast will not collide with 2D colliders. You need to use Physics2D Raycast for this purpose.

Video Tutorial

Raycast 2D script

using UnityEngine
public class raycast2dtest : MonoBehaviour
{
    RaycastHit2D hit;
    
    void FixedUpdate()
    {
         
         hit=Physics2D.Raycast(transform.position, Vector2.right);
                 
         Debug.Log(hit. Collider);
       
    }
}

Add a 2D collider to your gameobject which needs to interact with the Raycast. Also, Raycast in 2D can be set to detect its own Collider. You can enable this option from Edit>Project settings>Physics2d> Check Queries start in Colliders.

Unity Raycast 3D vs 2D

Raycast 3D	Raycast 2D
Physics.Raycast	Physics2D.Raycast
RaycastHit	RaycastHit2D
Raycast returns a Boolean when ray hits	Raycast2D returns the Hit data when ray hits
Position and direction input should be Vector3	Position and direction input should be Vector2
Interacts only with 3D colliders	Interacts only with 2D colliders

Common Reasons why your Raycast is not working in Unity

1. Trying to hit the wrong type of Collider. A 3D Raycast cannot hit a 2D collider and vice versa.
2. No collider attached to the object you are trying to hit.
3. The object is set as inactive.
4. Raycast is called within the Start function. You need to call it in the void Update or void FixedUpdate.
5. Timescale is set to 0.
6. The function name should be Physics.Raycast for a 3D game and Physics2D.Raycast for a 2D game.
7. Length of the Ray is smaller than the distance between the objects.
8. You are casting the Ray in the wrong direction.
9. The Unity Raycast origin in inside the collider.

Hope the post covered all the required aspects of Unity Raycast. You can shoot different shapes like sphere or box using Unity Spherecast and Boxcast, which are very similar to Raycast. If you have any questions, you can leave them in the comment section below.