three.js and confetti - vector

Question

I'm trying to make a confetti explosion and I'm having issues with projecting the confetti out. My idea is to have a fast explosion outwards in all directions (1 sec) then the confetti floats to the ground. I'm sure my math is wrong because I'm not getting it to expand.
I've taken three.js code and made some mods:
http://givememypatientinfo.com/ParticleBlocksConfetti.html
Any suggestions are welcome. I'm a noob at the three.js... but love the library!
Code:
var container, stats;
var camera, controls, scene, projector, renderer;
var objects = [], plane;
var vel = 1;
var vel2 = 0.01;
var accel = .3;
var accel2 = -.9;
var force = 1;
var frame = 0;
var mouse = new THREE.Vector2(),
offset = new THREE.Vector3(),
INTERSECTED, SELECTED;
init();
animate();
function init() {
container = document.createElement( 'div' );
document.body.appendChild( container );
camera = new THREE.PerspectiveCamera( 70, window.innerWidth / window.innerHeight, 1, 10000 );
camera.position.z = 1000;
/*//controls = new THREE.TrackballControls( camera );
controls.rotateSpeed = 1.0;
controls.zoomSpeed = 1.2;
controls.panSpeed = 0.8;
controls.noZoom = false;
controls.noPan = false;
controls.staticMoving = true;
controls.dynamicDampingFactor = 0.3;*/
scene = new THREE.Scene();
scene.add( new THREE.AmbientLight( 0x505050 ) );
var light = new THREE.SpotLight( 0xffffff, 1.5 );
light.position.set( 0, 500, 2000 );
light.castShadow = true;
light.shadowCameraNear = 200;
light.shadowCameraFar = camera.far;
light.shadowCameraFov = 50;
light.shadowBias = -0.00022;
light.shadowDarkness = 0.5;
light.shadowMapWidth = 2048;
light.shadowMapHeight = 2048;
scene.add( light );
var geometry = new THREE.CubeGeometry( 40, 40, 40 );
//make confetti for particle system
for ( var i = 0; i < 100; i ++ ) {
var object = new THREE.Mesh( geometry, new THREE.MeshLambertMaterial( { color: Math.random() * 0xffffff } ) );
//object.material.ambient = object.material.color;
/*object.position.x = Math.random() * 500 - 100;
object.position.y = Math.random() * 500 - 100;
object.position.z = 300;*/
object.position.x = Math.random() * 100 - 100;
object.position.y = Math.random() * 100 - 100;
object.position.z = 300;
object.rotation.x = Math.random() * 2 * Math.PI;
object.rotation.y = Math.random() * 2 * Math.PI;
object.rotation.z = Math.random() * 2 * Math.PI;
object.scale.x = .1;
object.scale.y = Math.random() * .8 + .1;
object.scale.z = Math.random() * .5 + .1;
object.castShadow = false;
object.receiveShadow = true;
scene.add( object );
objects.push( object );
}
plane = new THREE.Mesh( new THREE.PlaneGeometry( 2000, 2000, 8, 8 ), new THREE.MeshBasicMaterial( { color: 0x000000, opacity: 0.25, transparent: true, wireframe: true } ) );
plane.visible = false;
scene.add( plane );
projector = new THREE.Projector();
renderer = new THREE.WebGLRenderer( { antialias: true } );
renderer.sortObjects = false;
renderer.setSize( window.innerWidth, window.innerHeight );
renderer.shadowMapEnabled = true;
renderer.shadowMapType = THREE.PCFShadowMap;
container.appendChild( renderer.domElement );
var info = document.createElement( 'div' );
info.style.position = 'absolute';
info.style.top = '10px';
info.style.width = '100%';
info.style.textAlign = 'center';
info.innerHTML = 'three.js webgl - draggable cubes';
container.appendChild( info );
}
function animate_particles(frame) {
//will update each particle
if (frame < 50){
var pCount = objects.length-1;
if (frame < 40){
vel += accel*2;
}else {
vel = vel + accel2;
}
while(pCount > -1) {
if (frame < 30){
objects[pCount].position.y += vel;
}else{
objects[pCount].position.y -= vel;
}
//objects[pCount].rotation.x += Math.random()*.7;
//objects[pCount].rotation.z += Math.random()*.01;
//objects[pCount].rotation.y += Math.random()*.01;
pCount--;
}
}
}
function animate() {
requestAnimationFrame( animate );
animate_particles(frame);
render();
//stats.update();
}
function render() {
renderer.render( scene, camera );
frame++;
}
</script>

Answer 1

This could be what you were trying to archieve. I modified your code a little bit and commented the changes. Basically I just added a random direction vector, normalized it and added a random speed to the particles. In the animate_particles function, I am moving the confetti along the random direction vector at the random speed.
var container, stats;
var camera, controls, scene, projector, renderer;
var objects = [], plane;
var vel = 1;
var vel2 = 0.01;
var accel = .3;
var accel2 = -.9;
var force = 1;
var frame = 0;
var mouse = new THREE.Vector2(),
offset = new THREE.Vector3(),
INTERSECTED, SELECTED;
init();
animate();
function init() {
container = document.createElement( 'div' );
document.body.appendChild( container );
camera = new THREE.PerspectiveCamera( 70, window.innerWidth / window.innerHeight, 1, 10000 );
camera.position.z = 1000;
/*//controls = new THREE.TrackballControls( camera );
controls.rotateSpeed = 1.0;
controls.zoomSpeed = 1.2;
controls.panSpeed = 0.8;
controls.noZoom = false;
controls.noPan = false;
controls.staticMoving = true;
controls.dynamicDampingFactor = 0.3;*/
scene = new THREE.Scene();
scene.add( new THREE.AmbientLight( 0x505050 ) );
var light = new THREE.SpotLight( 0xffffff, 1.5 );
light.position.set( 0, 500, 2000 );
light.castShadow = true;
light.shadowCameraNear = 200;
light.shadowCameraFar = camera.far;
light.shadowCameraFov = 50;
light.shadowBias = -0.00022;
light.shadowDarkness = 0.5;
light.shadowMapWidth = 2048;
light.shadowMapHeight = 2048;
scene.add( light );
var geometry = new THREE.CubeGeometry( 40, 40, 40 );
//make confetti for particle system
for ( var i = 0; i < 100; i ++ ) {
var object = new THREE.Mesh( geometry, new THREE.MeshLambertMaterial( { color: Math.random() * 0xffffff } ) );
//object.material.ambient = object.material.color;
/*object.position.x = Math.random() * 500 - 100;
object.position.y = Math.random() * 500 - 100;
object.position.z = 300;*/
object.position.x = Math.random() * 100 - 100;
object.position.y = Math.random() * 100 - 100;
object.position.z = 300;
object.rotation.x = Math.random() * 2 * Math.PI;
object.rotation.y = Math.random() * 2 * Math.PI;
object.rotation.z = Math.random() * 2 * Math.PI;
object.scale.x = .1;
object.scale.y = Math.random() * .8 + .1;
object.scale.z = Math.random() * .5 + .1;
// give every "particle" a random expanding direction vector and normalize it to receive a length of 1.
object.directionVector = new THREE.Vector3( Math.random() - .5, Math.random() - .5, Math.random() - .5 )
object.directionVector.normalize();
// and a random expanding Speed
object.expandingSpeed = Math.random() * 100;
object.castShadow = false;
object.receiveShadow = true;
scene.add( object );
objects.push( object );
}
plane = new THREE.Mesh( new THREE.PlaneGeometry( 2000, 2000, 8, 8 ), new THREE.MeshBasicMaterial( { color: 0x000000, opacity: 0.25, transparent: true, wireframe: true } ) );
plane.visible = false;
scene.add( plane );
projector = new THREE.Projector();
renderer = new THREE.WebGLRenderer( { antialias: true } );
renderer.sortObjects = false;
renderer.setSize( window.innerWidth, window.innerHeight );
renderer.shadowMapEnabled = true;
renderer.shadowMapType = THREE.PCFShadowMap;
container.appendChild( renderer.domElement );
var info = document.createElement( 'div' );
info.style.position = 'absolute';
info.style.top = '10px';
info.style.width = '100%';
info.style.textAlign = 'center';
info.innerHTML = 'three.js webgl - draggable cubes';
container.appendChild( info );
}
function animate_particles(frame) {
//will update each particle
if (frame < 50){
var pCount = objects.length-1;
if (frame < 40){
vel += accel*2;
}else {
vel = vel + accel2;
}
while(pCount > -1) {
if (frame < 30){
// commented that out. not sure why you put it there.
//objects[pCount].position.y += vel;
// move objects along random direction vector at the individual random speed.
objects[pCount].position.x += objects[pCount].directionVector.x * objects[pCount].expandingSpeed;
objects[pCount].position.y += objects[pCount].directionVector.y * objects[pCount].expandingSpeed;
objects[pCount].position.z += objects[pCount].directionVector.z * objects[pCount].expandingSpeed;
}else{
objects[pCount].position.y -= vel;
}
//objects[pCount].rotation.x += Math.random()*.7;
//objects[pCount].rotation.z += Math.random()*.01;
//objects[pCount].rotation.y += Math.random()*.01;
pCount--;
}
}
}
function animate() {
requestAnimationFrame( animate );
animate_particles(frame);
render();
//stats.update();
}
function render() {
renderer.render( scene, camera );
frame++;
}

Answer 2

I've just made a plugin for create Confetti Effect with THREE.js: https://github.com/mrgoonie/three.confetti.explosion.js
Things would be easier with:
var confetti = new ExplosionConfetti({
rate: 1, // percent of explosion in every tick - smaller is fewer - be careful, larger than 10 may crash your browser!
amount: 200, // max amount particle of an explosion
radius: 800, // max radius of an explosion
areaWidth: 500, // width of the area
areaHeight: 500, // height of the area
fallingHeight: 500, // start exploding from Y position
fallingSpeed: 1, // max falling speed
colors: [0xffffff, 0xff0000, 0xffff00] // random colors
});
scene.add( confetti.object );
Cheers,