javascript - Drawing a line between moving objects -

i'm trying draw line between 2 moving vertices. vertex's drawing stored in variable called object, has position, three.vector3.

the line created thusly:

var line = function(scene, source, target){   var geometry = new three.geometry();   geometry.dynamic = true;   geometry.vertices.push(source.object.position);   geometry.vertices.push(target.object.position);   geometry.verticesneedupdate = true;    var material = new three.linebasicmaterial({ color: 0x000000 });   var line = new three.line( geometry, material );    scene.add(line);   return line; }; 

..., source , target vertices , vertices updated via:

vertex.object.position.add(vertex.velocity); 

now, assigned source.object.position , target.object.position line.geometry.vertices[0] , line.geometry.vertices[1] because wanted 1 update other. instead, vertex positions vary wildly line positions. vertices are, lines don't connect vertices.

how can make lines move vertices?

in animation loop have set line.geometry.verticesneedupdate = true. because every time after rendering becomes false. jsfiddle example