Making a 3D Object the Cursor

Unity Engine
1

How would I make a mesh follow the cursor, just along the X axis. Thank you!

2

This is what we’ve used. There’s probably a simpler way:

	/**
	* Where does our ray intersect a plane?
	* 
	* From [url]http://www.gamespp.com/algorithms/collisionDetectionTutorial02.html[/url]
	* @param	ray
	* @param	planeNormal
	* @param	planeD
	*/
	static function DistanceRayPlane(ray:Ray, planeNormal:Vector3, planeD:float)
	{
		var cosAlpha:float;
		var deltaD:float;
		
		cosAlpha = Vector3.Dot(ray.direction, planeNormal);
		
		if(cosAlpha == 0)
			return -1.0;
			
		deltaD = planeD - Vector3.Dot(ray.origin, planeNormal);
		
		return (deltaD / cosAlpha);
	}

function Update()
{
	var ray = Camera.main.ScreenPointToRay(Input.mousePosition);
	var mouse = ray.GetPoint(Helpers.DistanceRayPlane(ray, Vector3.forward, 0));
	
	transform.LookAt(mouse);
}

That’ll move an object around with Z=0.

The simpler solution is to do a raycast to a collider, but that can depend on your setup. I’ve found doing things purely mathematically is more portable.

3

That seems a little overly complicated to me, and it also gives me an “Unknown Identifier, Helpers”

4

Try this:

// CursorIcon.js
// Place this script onto the model you want to follow the cursor around.

enum Type {X, Y, XandY}
var type = Type.XandY;

// This is only used if you are using Type.Y.  It is the x position of it.
var xSpot = 0.0;

// This is always used.
var depth = 0.0;

// This is only used if you are using Type.X. It is the y position of it.
var height = 0.0;

private var helperCollider : GameObject;
function Start ()
{
	Screen.showCursor = false;
	helperCollider = GameObject ("HelperCollider");
	helperCollider.AddComponent (BoxCollider);
	helperCollider.collider.isTrigger = true;
	helperCollider.transform.localScale = Vector3 (50, 50, 0);
	helperCollider.transform.parent = camera.main.transform;
	helperCollider.transform.position = Vector3 (0, 0, depth);
	if (collider)
		Destroy (collider);
}

function Update ()
{
	var ray : Ray = camera.main.ScreenPointToRay (Input.mousePosition);
	var hit : RaycastHit;
	if (Physics.Raycast (ray, hit))
	{
		if (hit.collider == helperCollider.collider)
		{
			if (type == Type.X)
				transform.position = Vector3 (hit.point.x, height, depth);
				
			else
				if (type == Type.Y)
					transform.position = Vector3 (xSpot, hit.point.y, depth);
					
			else
				transform.position = Vector3 (hit.point.x, hit.point.y, depth);
		}
	}
}
5

Thanks dan. :smile:

6

This is what I used for my cake deal:

http://forum.unity3d.com/viewtopic.php?t=6431

var distanceFromCamera : float;

private var X : int;
private var Y : int;

// position a 3D object where the mouse cursor would be
function Update () {
     Screen.showCursor = false;
     X = Input.mousePosition.x;
     Y = Input.mousePosition.y;
     transform.position = camera.main.ScreenToWorldPoint(Vector3(X,Y,distanceFromCamera)); 
}

Instead of using Input.mousePosition.y, just insert the height up the game window you want the object to be. I would probably recommend using ViewportToWorldPoint so that it looks basically the same at all resolutions.

This is the easiest method I know of. Let me know if I can help out more.

7

Put the DistanceRayPlane() function in a “Helpers” script.

8

Jessy’s script is probably better than mine. I use an unnessasy collider.

Here’s a version of Jessy’s that I modifyed so you can choose wether you want it to follow on a certain mouse axis:

enum Type {X, Y, XandY}
var type = Type.XandY;

// This number ranges between 0 and 1.
// 1 is at the right of the screen, and 0 is a the left of the screen.
// This is only used if you are using Type.Y.
var xOffset = 0.5;

// This number ranges between 0 and 1.
// 1 is at the top of the screen, and 0 is a the bottom of the screen.
// This is only used if you are using Type.X.
var height = 0.5;

// This is the z distance from the camera.
var depth = 10.0;

function Start ()
{
	Screen.showCursor = false;
}

function Update ()
{
	var x = Input.mousePosition.x;
	var y = Input.mousePosition.y;
	var mainCam = camera.main;
	if (type == Type.X)
		transform.position = mainCam.ScreenToWorldPoint (Vector3 (x, height * Screen.height, depth));
	
	else
		if (type == Type.Y)
			transform.position = mainCam.ScreenToWorldPoint (Vector3 (0, y, depth));
	
	else
		transform.position = mainCam.ScreenToWorldPoint (Vector3 (x, y, depth));
	
	height = Mathf.Clamp01 (height);
	xOffset = Mathf.Clamp01 (xOffset);
}
9

Whoah! Nice!

Hopefully I’ll get a chance to try that out soon myself!