A ray that emits from an origin in a certain direction. This is used by the [page:Raycaster] to assist with [link:https://en.wikipedia.org/wiki/Ray_casting raycasting]. Raycasting is used for mouse picking (working out what objects in the 3D space the mouse is over) amongst other things.
		[page:Vector3 origin] - (optional) the origin of the [page:Ray]. Default is a [page:Vector3] at (0, 0, 0).
		[page:Vector3 direction] - [page:Vector3] The direction of the [page:Ray]. This must be normalized
		 (with [page:Vector3.normalize]) for the methods to operate properly.  Default is a [page:Vector3] at (0, 0, -1).
		Creates a new [name].
		
The origin of the [page:Ray]. Default is a [page:Vector3] at (0, 0, 0).
The direction of the [page:Ray]. This must be normalized (with [page:Vector3.normalize]) for the methods to operate properly. Default is a [page:Vector3] at (0, 0, -1).
		[page:Matrix4 matrix4] - the [page:Matrix4] to apply to this [page:Ray].
		Transform this [page:Ray] by the [page:Matrix4].
		
		[page:Float t] - the distance along the [page:Ray] to retrieve a position for.
		[page:Vector3 target] — the result will be copied into this Vector3.
		Get a [page:Vector3] that is a given distance along this [page:Ray].
		
Creates a new Ray with identical [page:.origin origin] and [page:.direction direction] to this one.
		[page:Vector3 point] - the point to get the closest approach to. 
		[page:Vector3 target] — the result will be copied into this Vector3.
		Get the point along this [page:Ray] that is closest to the [page:Vector3] provided.
		
Copies the [page:.origin origin] and [page:.direction direction] properties of [page:Ray ray] into this ray.
		[page:Vector3 point] - the [page:Vector3] to compute a distance to.
		Get the squared distance of the closest approach between the [page:Ray] and the [page:Vector3].
		
		[page:Vector3 v0] - the start of the line segment.
		[page:Vector3 v1] - the end of the line segment.
		optionalPointOnRay - (optional) if this is provided, it receives the point on this
			[page:Ray] that is closest to the segment.
		optionalPointOnSegment - (optional) if this is provided, it receives the point
			on the line segment that is closest to this [page:Ray].
		Get the squared distance between this [page:Ray] and a line segment.
		
		[page:Plane plane] - the [page:Plane] to get the distance to.
		Get the distance from [page:.origin origin] to the [page:Plane], or *null* if the [page:Ray] doesn't intersect the [page:Plane].
		
		[page:Vector3 point] - [page:Vector3] The [page:Vector3] to compute a distance to.
		Get the distance of the closest approach between the [page:Ray] and the [page:Vector3 point].
		
		[page:Ray ray] - the [page:Ray] to compare to.
		Returns true if this and the other [page:Ray ray] have equal [page:.offset offset]
		 and [page:.direction direction].
		
		[page:Box3 box] - the [page:Box3] to intersect with.
		[page:Vector3 target] — the result will be copied into this Vector3.
		Intersect this [page:Ray] with a [page:Box3], returning the intersection point or
		*null* if there is no intersection.
		
		[page:Plane plane] - the [page:Plane] to intersect with.
		[page:Vector3 target] — the result will be copied into this Vector3.
		Intersect this [page:Ray] with a [page:Plane], returning the intersection point or
		*null* if there is no intersection.
		
		[page:Sphere sphere] - the [page:Sphere] to intersect with.
		[page:Vector3 target] — the result will be copied into this Vector3.
		Intersect this [page:Ray] with a [page:Sphere], returning the intersection point or
		*null* if there is no intersection.
		
		[page:Vector3 a], [page:Vector3 b], [page:Vector3 c] - The [page:Vector3] points making up the triangle.
		[page:Boolean backfaceCulling] - whether to use backface culling.
		[page:Vector3 target] — the result will be copied into this Vector3.
		Intersect this [page:Ray] with a triangle, returning the intersection point or *null*
		if there is no intersection.
		
		[page:Box3 box] - the [page:Box3] to intersect with.
		Return true if this [page:Ray] intersects with the [page:Box3].
		
		[page:Plane plane] - the [page:Plane] to intersect with.
		Return true if this [page:Ray] intersects with the [page:Plane].
		
		[page:Sphere sphere] - the [page:Sphere] to intersect with.
		Return true if this [page:Ray] intersects with the [page:Sphere].
		
		[page:Vector3 v] - The [page:Vector3] to look at.
		Adjusts the direction of the ray to point at the vector in world coordinates.
		
		[page:Float t] - The distance along the [page:Ray] to interpolate.
		Shift the origin of this [page:Ray] along its direction by the distance given.
		
		[page:Vector3 origin] - the [page:.origin origin] of the [page:Ray].
		[page:Vector3 origin] - the [page:.direction direction] of the [page:Ray].
		This must be normalized (with [page:Vector3.normalize]) for the methods to operate
		properly.
		Sets this ray's [page:.origin origin] and [page:.direction direction] properties by copying the values from the given objects.
		
[link:https://github.com/mrdoob/three.js/blob/master/src/[path].js src/[path].js]