gistfile1.js

// 
//  planets.js 
//  
//  Created by Philip Rosedale on January 26, 2015
//  Copyright 2015 High Fidelity, Inc.
//  
//  Some planets are created in front of you.  A physical object shot or thrown between them will move 
//  correctly.  
// 
//  Distributed under the Apache License, Version 2.0.
//  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
//

var MAX_RANGE = 75.0; 
var MAX_TRANSLATION = MAX_RANGE / 20.0;

var LIFETIME = 600;    
var DAMPING = 0.0;
var G = 3.0;

//  In this section, setup where you want your 'Planets' that will exert gravity on the 
//  smaller test particles.  Use the first one for the simplest 'planets around sun' simulation.  
//  Add additional planets to make things a lot more complicated! 

var planetTypes = [];
planetTypes.push({ radius: 10, red: 0, green: 0, blue: 255, x: 0.0, y:0, z: 0.0 });

var center = Vec3.sum(MyAvatar.position, Vec3.multiply(MAX_RANGE, Quat.getFront(Camera.getOrientation())));

var NUM_INITIAL_PARTICLES = 100; 
var PARTICLE_MIN_SIZE = 0.50; 
var PARTICLE_MAX_SIZE = 4.50;
var INITIAL_VELOCITY = 5.0;
var DEGREES_TO_RADIANS = Math.PI / 180.0;

var planets = [];
var particles = [];

//  Create planets that will extert gravity on test particles 
for (var i = 0; i < planetTypes.length; i++) {
    // NOTE: rotationalVelocity is in radians/sec
    var position = { x: planetTypes[i].x, y: planetTypes[i].y, z: planetTypes[i].z };
    position = Vec3.multiply(MAX_RANGE / 2, position);
    position = Vec3.sum(center, position);
    
    planets.push(Entities.addEntity({ 
        type: "Sphere",
        position: position,  
        dimensions: { x: planetTypes[i].radius, y: planetTypes[i].radius, z: planetTypes[i].radius }, 
        color: { red: planetTypes[i].red, green: planetTypes[i].green, blue: planetTypes[i].blue },
        gravity: {  x: 0, y: 0, z: 0 },
        angularVelocity: {  x: 0, y: 0, z: 0 },
        angularDamping: 0.0,
        ignoreCollisions: true,
        lifetime: LIFETIME,
        collisionsWillMove: false 
    })); 
}

Script.setTimeout(createParticles, 1000); 

function createParticles() {
    //  Create initial test particles that will move according to gravity from the planets
    for (var i = 0; i < NUM_INITIAL_PARTICLES; i++) {
        var radius = PARTICLE_MIN_SIZE + Math.random() * PARTICLE_MAX_SIZE;
        var gray = Math.random() * 155;
        var whichPlanet = 0; 
        var position = { x: 10 , y: i * 3, z: 0 };
        var separation = Vec3.length(position);
		var color = { red: 100 + gray, green: 100 + gray, blue: 100 + gray };
		if (i == 0) {
			color = { red: 255, green: 0, blue: 0 };
			radius = 10
		}
        particles.push(Entities.addEntity({ 
            type: "Sphere",
            position: Vec3.sum(center, position),  
            dimensions: { x: radius, y: radius, z: radius }, 
            color: color,
            gravity: {  x: 0, y: 0, z: 0 },
            angularVelocity: {  x: 0, y: 0, z: 0 },
            velocity: {  x: 0, y: 0, z: 0 },
            ignoreCollisions: true,
            damping: DAMPING,
            lifetime: LIFETIME,
            collisionsWillMove: false 
        })); 
    }
    Script.update.connect(update);
}

function scriptEnding() {
    for (var i = 0; i < planetTypes.length; i++) {
        Entities.deleteEntity(planets[i]);
    }
    for (var i = 0; i < particles.length; i++) {
        Entities.deleteEntity(particles[i]);
    }
}

var totalTime = 0.0;
function update(deltaTime) {
    //  Apply gravitational force from planets
    totalTime += deltaTime;
    var planetProperties = Entities.getEntityProperties(planets[0]);
    var center = planetProperties.position;
    var particlePos = Entities.getEntityProperties(particles[0]).position;
    var relativePos = Vec3.subtract(particlePos.position, center);
    for (var t = 0; t < particles.length; t++) {
		var thetaDelta = (Math.PI * 2.0 / NUM_INITIAL_PARTICLES) * t;
		var y = Math.sin(totalTime + thetaDelta) * 10.0;
		var x = Math.cos(totalTime + thetaDelta) * 10.0;
		
        var newBasePos = Vec3.sum({ x: 0, y: y, z: x }, center);
        Entities.editEntity(particles[t], { position: newBasePos}); 
    }
}

Script.scriptEnding.connect(scriptEnding);