Retrieve a Line vector? [SOLVED]

Hello experts!

In a function, I have created some lines and pushed these in an array.

var line = new THREE.Line( lineGeom, lineMaterial );
linesArray.push( line);
scene.add( line );

In another function, I would like to loop through the array and get a sense of the angle between each line and the camera vector with the scalar product of the 2 vectors. I tried this:

for (var i = 0; i < linesArray.length; i++) {
           lineObj = linesArray[i];
    	   var dir = new THREE.Vector3(0,0,1);
    	   dir.applyQuaternion( lineObj.quaternion );

but I can’t get the line vector as I can with other kind of geometries. I also tried:

var matrix = new THREE.Matrix4();
matrix.extractRotation( lineObj.matrix );
var direction = new THREE.Vector3( 0, 0, 1 );

without better success.

Thank you for any help guys!

Found it! Simple.

dir.subVectors( lineObj.geometry.vertices[1], lineObj.geometry.vertices[0] ).normalize();