LineDashedMaterial - keep dashes the same length when changing line length - three.js

Question

I have a created a dashed line which changes position and length over time. To update it's position I'm adjusting the vertices of it's geometry object. This works great, except when the line becomes longer or shorter the dashes also get longer or shorter, despite being defined in absolute units, not relative to the length of the line.
I am already calling geometry.computeLineDistances() on initialisation (I have to do this to get the dashing to work at all), and I expected that if I simply called this in every render loop they would keep to the right scale, but that doesn't work.
Is there anything I can do to keep the dashes fixed length as the line changes length?
Here is a jsfiddle that illustrates the problem (code below): https://jsfiddle.net/fyr519L8/
var camera, scene, renderer, geometry, material, mesh;
init();
animate();
function init() {
scene = new THREE.Scene();
camera = new THREE.PerspectiveCamera(50, window.innerWidth / window.innerHeight, 1, 10000);
camera.position.set(0, 30, 0);
camera.lookAt(scene.position);
scene.add(camera);
geometry = new THREE.Geometry();
geometry.vertices.push(
new THREE.Vector3(0, 0, 0),
new THREE.Vector3(0, 0, 15));
geometry.computeLineDistances();
material = new THREE.LineDashedMaterial({
color: 0x000000,
dashSize: 1,
gapSize: 1,
linewidth: 1
});
mesh = new THREE.Line(geometry, material);
scene.add(mesh);
renderer = new THREE.WebGLRenderer();
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);
}
function animate() {
requestAnimationFrame(animate);
render();
}
function render() {
geometry.vertices[0].z = Math.sin(Date.now() / 1000) * 10;
geometry.verticesNeedUpdate = true;
renderer.render(scene, camera);
}

Answer 1

If I got you right, then you can do this:
function render() {
geometry.vertices[0].z = Math.sin(Date.now() / 1000) * 10;
geometry.verticesNeedUpdate = true;
geometry.computeLineDistances(); // re-calculate line distances
geometry.lineDistancesNeedUpdate = true;
renderer.render(scene, camera);
}
UPD#1 Method .computeLineDistances() has been moved from THREE.Geometry() to THREE.Line() (r94)