From dfb1cffbd702c45468392ee7c9f7d48d760d424f Mon Sep 17 00:00:00 2001
From: Philip Rosedale <philip@highfidelity.io>
Date: Fri, 30 Jan 2015 10:24:26 -0800
Subject: [PATCH] Add planet simulation

---
 examples/planets.js | 121 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 121 insertions(+)
 create mode 100644 examples/planets.js

diff --git a/examples/planets.js b/examples/planets.js
new file mode 100644
index 0000000000..87ed774c93
--- /dev/null
+++ b/examples/planets.js
@@ -0,0 +1,121 @@
+// 
+//  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: 15, red: 0, green: 0, blue: 255, x: 0.0, y:0, z: 0.0 });
+//planetTypes.push({ radius: 10, red: 0, green: 255, blue: 0, x: 0.60, y:0, z: 0.60 });
+//planetTypes.push({ radius: 10, red: 0, green: 0, blue: 255, x: 0.75, y:0, z: 0.75 });
+//planetTypes.push({ radius: 5, red: 255, green: 0, blue: 0, x: 0.25, y:0, z: 0.25 });
+//planetTypes.push({ radius: 5, red: 0, green: 255, blue: 255, x: 0, y:0, z: 0 });
+
+var center = Vec3.sum(MyAvatar.position, Vec3.multiply(MAX_RANGE, Quat.getFront(Camera.getOrientation())));
+
+var NUM_INITIAL_PARTICLES = 200; 
+var PARTICLE_MIN_SIZE = 0.50; 
+var PARTICLE_MAX_SIZE = 1.50;
+var INITIAL_VELOCITY = 5.0;
+
+var planets = [];
+var particles = [];
+
+//  Create planets that will extert gravity on test particles 
+for (var i = 0; i < planetTypes.length; i++) {
+	var rotationalVelocity = 10 + Math.random() * 60;
+	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: rotationalVelocity, z: 0 },
+	      	angularDamping: 0.0,
+	        ignoreCollisions: false,
+	        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 = Math.floor(Math.random() * planets.length); 
+		var position = { x: (Math.random() - 0.5) * MAX_RANGE, y: (Math.random() - 0.5) * MAX_TRANSLATION, z: (Math.random() - 0.5) * MAX_RANGE };
+		var separation = Vec3.length(position);
+		particles.push(Entities.addEntity(
+		    	{ type: "Sphere",
+		        position: Vec3.sum(center, position),  
+				dimensions: { x: radius, y: radius, z: radius }, 
+		      	color: { red: 100 + gray, green: 100 + gray, blue: 100 + gray },
+		      	gravity: {  x: 0, y: 0, z: 0 },
+		      	angularVelocity: {  x: 0, y: 0, z: 0 },
+		      	velocity: Vec3.multiply(INITIAL_VELOCITY * Math.sqrt(separation), Vec3.normalize(Vec3.cross(position, { x: 0, y: 1, z: 0 }))),
+		        ignoreCollisions: false,
+		        damping: DAMPING,
+		        lifetime: LIFETIME,
+		        collisionsWillMove: true })); 
+	}
+	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]);
+	}
+}
+
+function update(deltaTime) {
+	//  Apply gravitational force from planets  
+	for (var t = 0; t < particles.length; t++) {
+		var properties1 = Entities.getEntityProperties(particles[t]);
+		var velocity = properties1.velocity;
+		var vColor = Vec3.length(velocity) / 50 * 255;
+		var dV = { x:0, y:0, z:0 };
+		var mass1 = Math.pow(properties1.dimensions.x / 2.0, 3.0);
+		for (var p = 0; p < planets.length; p++) {
+			var properties2 = Entities.getEntityProperties(planets[p]);
+			var mass2 = Math.pow(properties2.dimensions.x / 2.0, 3.0);
+			var between = Vec3.subtract(properties1.position, properties2.position);
+			var separation = Vec3.length(between);
+			dV = Vec3.sum(dV, Vec3.multiply(-G * mass1 * mass2 / separation, Vec3.normalize(between))); 
+		}
+		if (Math.random() < 0.1) {
+			Entities.editEntity(particles[t], { color: { red: vColor, green: 100, blue: (255 - vColor) }, velocity: Vec3.sum(velocity, Vec3.multiply(deltaTime, dV))}); 
+		} else {
+			Entities.editEntity(particles[t], { velocity: Vec3.sum(velocity, Vec3.multiply(deltaTime, dV))});
+		}
+		
+	}
+}
+
+Script.scriptEnding.connect(scriptEnding);
\ No newline at end of file