Rotating an object to face the mouse location?

Hey guys, what I'm trying to do, in theory is take an object that is restricted to 2d space (z is 0 always) and I want to make that object rotate to face the mouse pointer, I've done this in flash and in C using opengl. I think the confusion I'm having is getting the position of the cursor in world space. This is what I currently have, I've tried several trials and I'm finally giving in and asking for help

Code (csharp):

1. function Update ()
2. {
3.     mousePos = Camera.main.ScreenToWorldPoint(new Vector3(Input.mousePosition.x, Input.mousePosition.y, 0));
4.  
5.     v = theCamera.transform.position - mousePos;
6.  
7.     transform.LookAt(transform.position - v);
8.  
9.     // look = transform.position - mousePos;
10.     //  transform.rotation = look;
11.  
12.     if (Input.GetButtonDown("Fire1")) {
13.         ShootCannon();
14.     }
15. }

Let me know if I'm even on the right track with this... thanks in advance!

 

In case anybody else is trying to figure this out, here's what I finally came up with that works great. :wink:

Code (csharp):

1. var target : Transform;
2. var strength = 5;
3.  
4. function Update () {
5.  
6.   zCam = -Camera.main.transform.position.z;
7.   var mouseVector = Vector3(Input.mousePosition.x, Input.mousePosition.y, zCam);
8.   var mPos = Camera.main.ScreenToWorldPoint(mouseVector);
9.    
10.   targetRotation = Quaternion.LookRotation (mPos - transform.position);
11.   targetRotation.x = 0.0;
12.   targetRotation.y = 0.0;
13.    
14.    
15.   str = Mathf.Min (strength * Time.deltaTime, 1);
16.   transform.rotation = Quaternion.Lerp (transform.rotation, targetRotation, str);  
17. }

 

I'm having a similar problem. Camera.main.ScreenToWorldPoint() only ever returns the camera's world position no matter what vector I use as a parameter.

I'm sure I've done something stupid and possibly illegal in more than one country. But I can't figure out why it ignores the vectors I give it to convert (ie, current Input.mousePosition).

 

Just as I posted for more help, I realized that changing the Z to -Camera.main.transform.position.z will correct my problem. I have no idea why, but it works.

Here's my code, which is a bit different from the above.

Code (csharp):

1.  
2. Vector3 mouseScreenPosition = new Vector3( Input.mousePosition.x, Input.mousePosition.y, -Camera.main.transform.position.z );
3.  
4. mouseWorldPosition = Camera.main.ScreenToWorldPoint( mouseScreenPosition );
5.  
6. transform.LookAt( mouseWorldPosition, Vector3.up );

 

In the vector you send to ScreenToWorldPoint are you always setting the z component to 0? That will just give you the camera transform every time.

In world space, screen points correspond to rays going from the camera's position off into the distance. The z value you put in is basically the distance from the origin, and at 0 distance it will always just be the camera's position. To get a useable point you have to specify a distance (z value) at which to calculate the position.

 

Ok, so because it's a ray (I thought it was just computing a point by converting the coordinates directly), without a distance (ie, Z = 0) it doesn't go anywhere. That makes sense. Thanks for the explanation.

 

Wow, finding this code just made my day. Just one question, when I apply this code to my model...it rotates around first (facing diagonally backwards), is there a way to fix this (like an offest or something). I know it should be a simple fix, just dont understand the code well enough to do it myself (tried adding/subtracting values to the z coordinate, but no such luck).

Im using the code from croebot, btw.

Thanks

 

I did this with the following few lines of code(c#) in the update function

Code (csharp):

1.  
2. float h = Input.mousePosition.x - Screen.width / 2;
3. float v = Input.mousePosition.y - Screen.height / 2;
4. float angle = -Mathf.Atan2(v,h) * Mathf.Rad2Deg;
5.        
6. transform.rotation = Quaternion.Euler (270, angle, 0);
7.  

put the angle variable on whichever axis you would like it to rotate around and attach the script to the object you would like to rotate.