vel.findIntersection(ref, target)

Find the intersection of a line starting in the center of the SVG node ending in the point ref (an object of the form { x: Number, y: Number }). target is an SVG element to which this node's transformations are relative to. In JointJS, target is usually the paper.viewport SVG group element. Note that ref point must be in the coordinate system of the target for this function to work properly. This function returns a point in the target coordinte system (the same system as ref is in) if an intersection is found. Returns undefined otherwise.