closestPointToPointParameter( point, clampToLine ) {

		_startP.subVectors( point, this.start );
		_startEnd.subVectors( this.end, this.start );

		const startEnd2 = _startEnd.dot( _startEnd );
		const startEnd_startP = _startEnd.dot( _startP );

		let t = startEnd_startP / startEnd2;

		if ( clampToLine ) {

			t = clamp( t, 0, 1 );

		}

		return t;

	}
Returns a point parameter based on the closest point as projected on the line segment.

@param {Vector3} point - The point for which to return a point parameter.
@param {boolean} clampToLine - Whether to clamp the result to the range `[0,1]` or not.
@return {number} The point parameter.