In the section Understanding the View Frustum, it was explained that any point in the camera’s view corresponds to a line in world space. It is sometimes useful to have a mathematical representation of that line and Unity can provide this in the form of a Ray object. The Ray always corresponds to a point in the view, so the Camera class provides the ScreenPointToRay and ViewportPointToRay functions. The difference between the two is that ScreenPointToRay expects the point to be provided as a pixel coordinate, while ViewportPointToRay takes normalized coordinates in the range 0..1 (where 0 represents the bottom or left and 1 represents the top or right of the view). Each of these functions returns a Ray which consists of a point of origin and a vector which shows the direction of the line from that origin. The Ray originates from the near clipping plane rather than the Camera’s transform.position point.
The most common use of a Ray from the camera is to perform a raycast out into the scene. A raycast sends an imaginary “laser beam” along the ray from its origin until it hits a collider in the scene. Information is then returned about the object and the point that was hit in a RaycastHit object. This is a very useful way to locate an object based on its onscreen image. For example, the object at the mouse position can be determined with the following code:
C# script example:
using UnityEngine;
using System.Collections;
public class ExampleScript : MonoBehaviour {
public Camera camera;
void Start(){
RaycastHit hit;
Ray ray = camera.ScreenPointToRay(Input.mousePosition);
if (Physics.Raycast(ray, out hit)) {
Transform objectHit = hit.transform;
// Do something with the object that was hit by the raycast.
}
}
}
JS script example:
var hit: RaycastHit;
var ray: Ray = camera.ScreenPointToRay(Input.mousePosition);
if (Physics.Raycast(ray, hit)) {
var objectHit: Transform = hit.transform;
// Do something with the object that was hit by the raycast.
}
It is sometimes useful to get a ray corresponding to a screen position and then move the camera along that ray. For example, you may want to allow the user to select an object with the mouse and then zoom in on it while keeping it “pinned” to the same screen position under the mouse (this might be useful when the camera is looking at a tactical map, for example). The code to do this is fairly straightforward:
C# script example:
using UnityEngine;
using System.Collections;
public class ExampleScript : MonoBehaviour {
public bool zooming;
public float zoomSpeed;
public Camera camera;
void Update() {
if (zooming) {
Ray ray = camera.ScreenPointToRay(Input.mousePosition);
float zoomDistance = zoomSpeed * Input.GetAxis("Vertical") * Time.deltaTime;
camera.transform.Translate(ray.direction * zoomDistance, Space.World);
}
}
}
JS script example:
var zooming: boolean;
var zoomSpeed: float;
if (zooming) {
var ray: Ray = camera.ScreenPointToRay(Input.mousePosition);
zoomDistance = zoomSpeed * Input.GetAxis("Vertical") * Time.deltaTime;
camera.transform.Translate(ray.direction * zoomDistance, Space.World);
}
Did you find this page useful? Please give it a rating:
Thanks for rating this page!
What kind of problem would you like to report?
Is something described here not working as you expect it to? It might be a Known Issue. Please check with the Issue Tracker at issuetracker.unity3d.com.
Thanks for letting us know! This page has been marked for review based on your feedback.
If you have time, you can provide more information to help us fix the problem faster.
Provide more information
You've told us this page needs code samples. If you'd like to help us further, you could provide a code sample, or tell us about what kind of code sample you'd like to see:
You've told us there are code samples on this page which don't work. If you know how to fix it, or have something better we could use instead, please let us know:
You've told us there is information missing from this page. Please tell us more about what's missing:
You've told us there is incorrect information on this page. If you know what we should change to make it correct, please tell us:
You've told us this page has unclear or confusing information. Please tell us more about what you found unclear or confusing, or let us know how we could make it clearer:
You've told us there is a spelling or grammar error on this page. Please tell us what's wrong:
You've told us this page has a problem. Please tell us more about what's wrong:
Thanks for helping to make the Unity documentation better!