Spawn Objects Where i click

Question

Basically i have a script written to where i have a gameobject and i have a simple 2x4 wood cube/model attached to it. I dont understand why when i click it spawns that object where the camera is and not where im pointing... All help is appreciated thanks

Heres my code

 public GameObject Wood;
     public bool isWood = true;
     public GameObject Metal;
     public bool isMetal = false;
     
     public Transform spawn;
     
     
     RaycastHit hit;
     public GameObject target;
     
     
     // Use this for initialization
     void Start () {
         
         target = Wood;
     }
     
     // Update is called once per frame
     void Update () {
         
         if (Input.GetMouseButtonDown(0)){
             Ray ray = Camera.main.ScreenPointToRay(new Vector3(Input.mousePosition.x, Input.mousePosition.y, 0));
                 if (Physics.Raycast(ray)){
                 
                 }
                         Instantiate(target, ray.origin, Quaternion.identity);
             
           }
     }

Theres more code than that but all the other code is unnecessary to include. I dont get any errors this just doesnt work.

Answer 1

Answer by fonql · Apr 20, 2013 at 03:46 PM

Actually, I got it working without having to cast a ray. The trick is to pass the INVERSE z position of your camera in the ScreenToWorldPoint last argument. So if your camera's z position is -10, pass 10. Here's my C# code:

 using UnityEngine;
 using System.Collections;
 
 public class MousePick : MonoBehaviour {
     
    public GameObject cuber;
     
     void Update() {
        
         if (Input.GetButtonDown("Fire1")) {
              print(Input.mousePosition);
              Vector3 p = Camera.main.**ScreenToWorldPoint(new Vector3(Input.mousePosition.x, Input.mousePosition.y,10.0f));
             print(p);
             print(p.x);
             print(p.y);
             
             Instantiate(cuber,new Vector3(p.x,p.y, 0.0f),Quaternion.identity);
             
         }
     }
 }

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asafsitner · Apr 20, 2013 at 04:00 PM 0

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How do you calculate the camera's Z position in relation to the surface you click on?

fonql · Apr 20, 2013 at 04:11 PM 0

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Well spotted Sir! I derive the z position simply from camera.transform.position.z; HOWEVER this is not the distance between a camera and a ray hitpoint, for that I suggest your script:) Agreed, my script is only helpful for 2d games.

asafsitner · Apr 20, 2013 at 05:05 PM 0

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Wouldn't it make sense to simply use -camera.position.z as the Z parameter of the ScreenToWorldPoint method to make it more generic?

That way you can theoretically support camera zoom, and avoid magic numbers in the code. ^^

fonql · Apr 20, 2013 at 05:40 PM 1

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Absolutely Agreed.

Answer 2

Answer by asafsitner · Jan 05, 2012 at 07:57 AM

That's because you Instantiate the objects at the ray's origin, i.e. the camera in your case as it's the object shooting the ray. You want to add `hitInfo` and spawn the object at `hitInfo.point`.

 if (Input.GetMouseButtonDown(0))
 {
     if (Physics.Raycast(Camera.main.ScreenPointToRay(new Vector3(Input.mousePosition.x, Input.mousePosition.y, 0), out rayInfo))
     {
         Instantiate(target, rayInfo.point, Quaternion.identity);
     }
 }

I also don't understand why you put the Instantiate call outside the if statement's block so I put it back in. If it's a mistake ignore it.

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Spawn Objects Where i click

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