God Of Mercy | Home Page IV

window.addEventListener(“load”, windowLoadHandler, false);

//for debug messages
var Debugger = function() { };
Debugger.log = function(message) {
try {
console.log(message);
}
catch (exception) {
return;
}
}

function windowLoadHandler() {
canvasApp();
}

function canvasSupport() {
return Modernizr.canvas;
}

function canvasApp() {
if (!canvasSupport()) {
return;
}

var theCanvas = document.getElementById(“canvasOne”);
var context = theCanvas.getContext(“2d”);

var displayWidth;
var displayHeight;
var timer;
var wait;
var count;
var numToAddEachFrame;
var particleList;
var recycleBin;
var particleAlpha;
var r,g,b;
var fLen;
var m;
var projCenterX;
var projCenterY;
var zMax;
var turnAngle;
var turnSpeed;
var sphereRad, sphereCenterX, sphereCenterY, sphereCenterZ;
var particleRad;
var zeroAlphaDepth;
var randAccelX, randAccelY, randAccelZ;
var gravity;
var rgbString;
//we are defining a lot of variables used in the screen update functions globally so that they don’t have to be redefined every frame.
var p;
var outsideTest;
var nextParticle;
var sinAngle;
var cosAngle;
var rotX, rotZ;
var depthAlphaFactor;
var i;
var theta, phi;
var x0, y0, z0;

init();

function init() {
wait = 1;
count = wait – 1;
numToAddEachFrame = 8;

//particle color
r = 204;
g = 0;
b = 204;

rgbString = “rgba(“+r+”,”+g+”,”+b+”,”; //partial string for color which will be completed by appending alpha value.
particleAlpha = 1; //maximum alpha

displayWidth = theCanvas.width;
displayHeight = theCanvas.height;

fLen = 180; //represents the distance from the viewer to z=0 depth.

//projection center coordinates sets location of origin
projCenterX = displayWidth/2;
projCenterY = displayHeight/2;

//we will not draw coordinates if they have too large of a z-coordinate (which means they are very close to the observer).
zMax = fLen-2;

particleList = {};
recycleBin = {};

//random acceleration factors – causes some random motion
randAccelX = 0.1;
randAccelY = 0.1;
randAccelZ = 0.1;

gravity = -0.0; //try changing to a positive number (not too large, for example 0.3), or negative for floating upwards.

particleRad = 2.5;
sphereRad = 280;
sphereCenterX = 0;
sphereCenterY = 0;
sphereCenterZ = -3 – sphereRad;

//alpha values will lessen as particles move further back, causing depth-based darkening:
zeroAlphaDepth = -750;

turnSpeed = 3*Math.PI/1600; //the sphere will rotate at this speed (one complete rotation every 1600 frames).
turnAngle = 0; //initial angle

timer = setInterval(onTimer, 1000/24);
}

function onTimer() {
//if enough time has elapsed, we will add new particles.
count++;
if (count >= wait) {

count = 0;
for (i = 0; i < numToAddEachFrame; i++) {
theta = Math.random()*2*Math.PI;
phi = Math.acos(Math.random()*2-1);
x0 = sphereRad*Math.sin(phi)*Math.cos(theta);
y0 = sphereRad*Math.sin(phi)*Math.sin(theta);
z0 = sphereRad*Math.cos(phi);

//We use the addParticle function to add a new particle. The parameters set the position and velocity components.
//Note that the velocity parameters will cause the particle to initially fly outwards away from the sphere center (after
//it becomes unstuck).
var p = addParticle(x0, sphereCenterY + y0, sphereCenterZ + z0, 0.002*x0, 0.002*y0, 0.002*z0);

//we set some “envelope” parameters which will control the evolving alpha of the particles.
p.attack = 50;
p.hold = 50;
p.decay = 60;
p.initValue = 0;
p.holdValue = particleAlpha;
p.lastValue = 0;

//the particle will be stuck in one place until this time has elapsed:
p.stuckTime = 80 + Math.random()*20;

p.accelX = 0;
p.accelY = gravity;
p.accelZ = 0;
}
}

//update viewing angle
turnAngle = (turnAngle + turnSpeed) % (2*Math.PI);
sinAngle = Math.sin(turnAngle);
cosAngle = Math.cos(turnAngle);

//background fill

context.fillStyle = “#f0eade;”;
context.fillRect(0,0,displayWidth,displayHeight);

//update and draw particles
p = particleList.first;
while (p != null) {
//before list is altered record next particle
nextParticle = p.next;

//update age
p.age++;

//if the particle is past its “stuck” time, it will begin to move.
if (p.age > p.stuckTime) {
p.velX += p.accelX + randAccelX*(Math.random()*2 – 1);
p.velY += p.accelY + randAccelY*(Math.random()*2 – 1);
p.velZ += p.accelZ + randAccelZ*(Math.random()*2 – 1);

p.x += p.velX;
p.y += p.velY;
p.z += p.velZ;
}

/*
We are doing two things here to calculate display coordinates.
The whole display is being rotated around a vertical axis, so we first calculate rotated coordinates for
x and z (but the y coordinate will not change).
Then, we take the new coordinates (rotX, y, rotZ), and project these onto the 2D view plane.
*/
rotX = cosAngle*p.x + sinAngle*(p.z – sphereCenterZ);
rotZ = -sinAngle*p.x + cosAngle*(p.z – sphereCenterZ) + sphereCenterZ;
m = fLen/(fLen – rotZ);
p.projX = rotX*m + projCenterX;
p.projY = p.y*m + projCenterY;

//update alpha according to envelope parameters.
if (p.age < p.attack+p.hold+p.decay) {
if (p.age < p.attack) {
p.alpha = (p.holdValue – p.initValue)/p.attack*p.age + p.initValue;
}
else if (p.age < p.attack+p.hold) {
p.alpha = p.holdValue;
}
else if (p.age < p.attack+p.hold+p.decay) {
p.alpha = (p.lastValue – p.holdValue)/p.decay*(p.age-p.attack-p.hold) + p.holdValue;
}
}
else {
p.dead = true;
}

//see if the particle is still within the viewable range.
if ((p.projX > displayWidth)||(p.projX<0)||(p.projY<0)||(p.projY>displayHeight)||(rotZ>zMax)) {
outsideTest = true;
}
else {
outsideTest = false;
}

if (outsideTest||p.dead) {
recycle(p);
}

else {
//depth-dependent darkening
depthAlphaFactor = (1-rotZ/zeroAlphaDepth);
depthAlphaFactor = (depthAlphaFactor > 1) ? 1 : ((depthAlphaFactor<0) ? 0 : depthAlphaFactor);
context.fillStyle = rgbString + depthAlphaFactor*p.alpha + “)”;

//draw
context.beginPath();
context.arc(p.projX, p.projY, m*particleRad, 0, 2*Math.PI, false);
context.closePath();
context.fill();
}

p = nextParticle;
}
}

function addParticle(x0,y0,z0,vx0,vy0,vz0) {
var newParticle;
var color;

//check recycle bin for available drop:
if (recycleBin.first != null) {
newParticle = recycleBin.first;
//remove from bin
if (newParticle.next != null) {
recycleBin.first = newParticle.next;
newParticle.next.prev = null;
}
else {
recycleBin.first = null;
}
}
//if the recycle bin is empty, create a new particle (a new ampty object):
else {
newParticle = {};
}

//add to beginning of particle list
if (particleList.first == null) {
particleList.first = newParticle;
newParticle.prev = null;
newParticle.next = null;
}
else {
newParticle.next = particleList.first;
particleList.first.prev = newParticle;
particleList.first = newParticle;
newParticle.prev = null;
}

//initialize
newParticle.x = x0;
newParticle.y = y0;
newParticle.z = z0;
newParticle.velX = vx0;
newParticle.velY = vy0;
newParticle.velZ = vz0;
newParticle.age = 0;
newParticle.dead = false;
if (Math.random() < 0.5) {
newParticle.right = true;
}
else {
newParticle.right = false;
}
return newParticle;
}

</script>