Legacy Documentation: Version 4.3.0
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Collider.Raycast
Raycast(ray: Ray, hitInfo: RaycastHit, distance: float): bool;
bool Raycast(Ray ray, RaycastHit hitInfo, float distance);
def Raycast(ray as Ray, hitInfo as RaycastHit, distance as float) as bool
Parameters

ray The starting point and direction of the ray.
hitInfo If true is returned, hitInfo will contain more information about where the collider was hit (See Also: RaycastHit).
distance The length of the ray.
Returns
bool True when the ray intersects any collider, otherwise false.
Description

Casts a Ray that ignores all Colliders except this one.

Same as above using /ray.origin/ and /ray.direction/ instead of origin and direction.
	// pragma below is needed due to a UnityJS issue
	#pragma strict
	function Update(){
	    var ray : Ray = Camera.main.ScreenPointToRay (Input.mousePosition);
	    var hit : RaycastHit;
	    if (collider.Raycast (ray, hit, 100.0)) {
	        Debug.DrawLine (ray.origin, hit.point);
	    }
	}