用p5.js制作煙花特效的示例代碼_javascript技巧

function setup() { //processing初始化設置
 createCanvas(window.innerWidth, window.innerHeight);
 frameRate(50);
 imageMode(CENTER);
}
function draw() { //循環執行，達成畫面渲染效果
 background(0, 0, 40);
 for (var i = 0; i < fireworks.length; i++) {
 fireworks[i].display();
 fireworks[i].update();
 if (fireworks[i].needRemove()) {
 fireworks.splice(i, 1);
 }
 }
}

function Fireworks(radius) {
 var num = 512; //一發煙花里，有多少個點 (比較吃機器)
 var centerPosition = new p5.Vector(random(width / 8, width * 7 / 8), random(height / 2, height * 4 / 5), random(-100, 100)); //煙花的中心位置
 var velocity = new p5.Vector(0, -22, 0);
 var accel = new p5.Vector(0, 0.4, 0);
 var img;
 var firePosition = [];
 var cosTheta;
 var sinTheta;
 var phi;
 var colorChange = random(0, 5);
 for (var i = 0; i < num; i++) {
 cosTheta = random(0, 1) * 2 - 1;
 sinTheta = sqrt(1 - cosTheta * cosTheta);
 phi = random(0, 1) * 2 * PI;
 firePosition[i] = new p5.Vector(radius * sinTheta * cos(phi), radius * sinTheta * sin(phi), radius * cosTheta); //1發煙花里各個點的位置計算
 firePosition[i] = p5.Vector.mult(firePosition[i], 1.12);
 }
 //調整煙花隨機顏色，使其更亮麗
 if(colorChange>=3.8){
 img=createLight(0.9,random(0.2,0.5),random(0.2,0.5));
 }else if(colorChange>3.2){
 img=createLight(random(0.2,0.5),0.9,random(0.2,0.5));
 }else if(colorChange>2){
 img=createLight(random(0.2,0.5),random(0.2,0.5),0.9);
 } else {
 img=createLight(random(0.5,0.8),random(0.5,0.8),random(0.5,0.8));
 }
 this.display = function () {
 for (var i = 0; i < num; i++) {
 push();
 translate(centerPosition.x, centerPosition.y, centerPosition.z);
 translate(firePosition[i].x, firePosition[i].y, firePosition[i].z);
 blendMode(ADD); //各個小點（發光源遮罩效果）
 image(img, 0, 0);
 pop();
 firePosition[i] = p5.Vector.mult(firePosition[i], 1.015); //更新小點（發光源）擴散位置
 } 
 }
 this.update = function () { //模擬重力加速度
 radius = dist(0, 0, 0, firePosition[0].x, firePosition[0].y, firePosition[0].z);
 centerPosition.add(velocity);
 velocity.add(accel);
 }
 this.needRemove = function () {
 if (centerPosition.y - radius > height) {
 return true;
 } else {
 return false;
 }
 }
}

function createLight(rPower, gPower, bPower) {
 var side = 64;
 var center = side / 2.0;
 var img = createImage(side, side);
 img.loadPixels();
 for (var y = 0; y < side; y++) {
 for (var x = 0; x < side; x++) {
 var distance = (sq(center - x) + sq(center - y)) / 10.0;
 var r = int((255 * rPower) / distance);
 var g = int((255 * gPower) / distance);
 var b = int((255 * bPower) / distance);
 // img.pixels[x + y * side] = color(r, g, b);
 img.set(y, x, color(r, g, b));
 }
 }
 img.updatePixels();
 return img;
}

function keyPressed() { //每事件添加一發煙花
 fireworks.push(new Fireworks(80)); //80為煙花初始半徑
}
function touchStarted() { //每事件添加一發煙花
 fireworks.push(new Fireworks(80));
 return false;
}