A curve representing a 3d line segment.
			[page:Vector3 v1] – The start point.
			[page:Vector3 v2] - The end point.
		
See the base [page:Curve] class for common properties.
			Used to check whether this or derived classes are LineCurve3s. Default is *true*.
			You should not change this, as it used internally for optimisation.
		
The start point.
The end point.
See the base [page:Curve] class for common methods.
[link:https://github.com/mrdoob/three.js/blob/master/src/[path].js src/[path].js]