import { ParticleSystem, DistanceConstraint } from 'particulate'

define(['particulate'], function (Particulate) { /* ... */ });

var Particulate = require('particulate');

var Particulate = window.Particulate;

// ..................................................
// Define particle chain system
//

var particleCount = 5;
var relaxIterations = 2;

var system = Particulate.ParticleSystem.create(particleCount, relaxIterations);
var dist = Particulate.DistanceConstraint.create(10, [0, 1, 1, 2, 2, 3, 3, 4]);
var pin = Particulate.PointConstraint.create([0, 0, 0], 0);
var gravity = Particulate.DirectionalForce.create([0, -0.05, 0]);

system.addConstraint(dist);
system.addPinConstraint(pin);
system.addForce(gravity);

// ..................................................
// Integrate with Three.js
//

var scene = new THREE.Scene();

// Use system positions buffer
var vertices = new THREE.BufferAttribute(system.positions, 3);

// Use distance constraint indices
var indices = new THREE.BufferAttribute(new Uint16Array(dist.indices));

// Particles
var dotsGeom = new THREE.BufferGeometry();
dotsGeom.addAttribute('position', vertices);

var dots = new THREE.PointCloud(dotsGeom,
  new THREE.PointCloudMaterial({ size : 2 }));

// Connections
var linesGeom = new THREE.BufferGeometry();
linesGeom.addAttribute('position', vertices);
linesGeom.addAttribute('index', indices);

var lines = new THREE.Line(linesGeom,
  new THREE.LineBasicMaterial());

scene.add(dots);
scene.add(lines);

function animate() {
  system.tick(1);
  dotsGeom.attributes.position.needsUpdate = true; // Flag to update WebGL buffer
  render();
}