本文实例讲述了JS实现基于Sketch.js模拟成群游动的蝌蚪运动动画效果。分享给大家供大家参考，具体如下：
基于Sketch.js，实现了物体触碰检测（蝌蚪会遇到障碍物以及聪明的躲避鼠标的点击），随机运动，聚集算法等。
已经具备了游戏的基本要素，扩展一下可以变成一个不错的 HTML5 游戏。
演示效果如下：
完整代码如下：
<!DOCTYPE html><html class=" -webkit- js flexbox canvas canvastext webgl no-touch geolocation postmessage websqldatabase indexeddb hashchange history draganddrop websockets rgba hsla multiplebgs backgroundsize borderimage borderradius boxshadow textshadow opacity cssanimations csscolumns cssgradients cssreflections csstransforms csstransforms3d csstransitions fontface generatedcontent video audio localstorage sessionstorage webworkers applicationcache svg inlinesvg smil svgclippaths"><head><meta charset="UTF-8"><title>HTML5 Preview Panel</title><script src="prefixfree.min.js"></script><script src="modernizr.js"></script><style>body { background-color: #222;}</style></head><body><script src="sketch.min.js"></script><div id="container"><canvas class="sketch" id="sketch-0" height="208" width="607"></canvas></div><script>var calculateDistance = function(object1, object2) { x = Math.abs(object1.x - object2.x); y = Math.abs(object1.y - object2.y); return Math.sqrt((x * x) + (y * y));};var calcMagnitude = function(x, y) { return Math.sqrt((x * x) + (y * y));};var calcVectorAdd = function(v1, v2) { return { x: v1.x + v2.x, y: v1.y + v2.y };};var random = function(min, max) { return min + Math.random() * (max - min);};var getRandomItem = function(list, weight) { var total_weight = weight.reduce(function(prev, cur, i, arr) { return prev + cur; }); var random_num = random(0, total_weight); var weight_sum = 0; //console.log(random_num) for (var i = 0; i < list.length; i++) { weight_sum += weight[i]; weight_sum = +weight_sum.toFixed(2); if (random_num <= weight_sum) { return list[i]; } } // end of function};/***********************BOID***********************/function Boid(x, y) { this.init(x, y);}Boid.prototype = { init: function(x, y) { //body this.type = "boid"; this.alive = true; this.health = 1; this.maturity = 4; this.speed = 6; this.size = 5; this.hungerLimit = 12000; this.hunger = 0; this.isFull = false; this.digestTime = 400; this.color = 'rgb(' + ~~random(0, 100) + ',' + ~~random(50, 220) + ',' + ~~random(50, 220) + ')'; //brains this.eyesight = 100; //range for object dectection this.personalSpace = 20; //distance to avoid safe objects this.flightDistance = 60; //distance to avoid scary objects this.flockDistance = 100; //factor that determines how attracted the boid is to the center of the flock this.matchVelFactor = 6; //factor that determines how much the flock velocity affects the boid. less = more matching this.x = x || 0.0; this.y = y || 0.0; this.v = { x: random(-1, 1), y: random(-1, 1), mag: 0 }; this.unitV = { x: 0, y: 0, }; this.v.mag = calcMagnitude(this.v.x, this.v.y); this.unitV.x = (this.v.x / this.v.mag); this.unitV.y = (this.v.y / this.v.mag); }, wallAvoid: function(ctx) { var wallPad = 10; if (this.x < wallPad) { this.v.x = this.speed; } else if (this.x > ctx.width - wallPad) { this.v.x = -this.speed; } if (this.y < wallPad) { this.v.y = this.speed; } else if (this.y > ctx.height - wallPad) { this.v.y = -this.speed; } }, ai: function(boids, index, ctx) { percievedCenter = { x: 0, y: 0, count: 0 }; percievedVelocity = { x: 0, y: 0, count: 0 }; mousePredator = { x: ((typeof ctx.touches[0] === "undefined") ? 0 : ctx.touches[0].x), y: ((typeof ctx.touches[0] === "undefined") ? 0 : ctx.touches[0].y) }; for (var i = 0; i < boids.length; i++) { if (i != index) { dist = calculateDistance(this, boids[i]); //Find all other boids close to it if (dist < this.eyesight) { //if the same species then flock if (boids[i].type == this.type) { //Alignment percievedCenter.x += boids[i].x; percievedCenter.y += boids[i].y; percievedCenter.count++; //Cohesion percievedVelocity.x += boids[i].v.x; percievedVelocity.y += boids[i].v.y; percievedVelocity.count++; //Separation if (dist < this.personalSpace + this.size + this.health) { this.avoidOrAttract("avoid", boids[i]); } } else { //if other species fight or flight if (dist < this.size + this.health + boids[i].size + boids[i].health) { this.eat(boids[i]); } else { this.handleOther(boids[i]); } } } //if close enough } //dont check itself } //Loop through boids //Get the average for all near boids if (percievedCenter.count > 0) { percievedCenter.x = ((percievedCenter.x / percievedCenter.count) - this.x) / this.flockDistance; percievedCenter.y = ((percievedCenter.y / percievedCenter.count) - this.y) / this.flockDistance; this.v = calcVectorAdd(this.v, percievedCenter); } if (percievedVelocity.count > 0) { percievedVelocity.x = ((percievedVelocity.x / percievedVelocity.count) - this.v.x) / this.matchVelFactor; percievedVelocity.y = ((percievedVelocity.y / percievedVelocity.count) - this.v.y) / this.matchVelFactor; this.v = calcVectorAdd(this.v, percievedVelocity); } //Avoid Mouse if (calculateDistance(mousePredator, this) < this.eyesight) { var mouseModifier = 20; this.avoidOrAttract("avoid", mousePredator, mouseModifier); } this.wallAvoid(ctx); this.limitVelocity(); }, setUnitVector: function() { var magnitude = calcMagnitude(this.v.x, this.v.y); this.v.x = this.v.x / magnitude; this.v.y = this.v.y / magnitude; }, limitVelocity: function() { this.v.mag = calcMagnitude(this.v.x, this.v.y); this.unitV.x = (this.v.x / this.v.mag); this.unitV.y = (this.v.y / this.v.mag); if (this.v.mag > this.speed) { this.v.x = this.unitV.x * this.speed; this.v.y = this.unitV.y * this.speed; } }, avoidOrAttract: function(action, other, modifier) { var newVector = { x: 0, y: 0 }; var direction = ((action === "avoid") ? -1 : 1); var vModifier = modifier || 1; newVector.x += ((other.x - this.x) * vModifier) * direction; newVector.y += ((other.y - this.y) * vModifier) * direction; this.v = calcVectorAdd(this.v, newVector); }, move: function() { this.x += this.v.x; this.y += this.v.y; if (this.v.mag > this.speed) { this.hunger += this.speed; } else { this.hunger += this.v.mag; } }, eat: function(other) { if (!this.isFull) { if (other.type === "plant") { other.health--; this.health++; this.isFull = true; this.hunger = 0; } } }, handleOther: function(other) { if (other.type === "predator") { this.avoidOrAttract("avoid", other); } }, metabolism: function() { if (this.hunger >= this.hungerLimit) { this.health--; this.hunger = 0; } if (this.hunger >= this.digestTime) { this.isFull = false; } if (this.health <= 0) { this.alive = false; } }, mitosis: function(boids) { if (this.health >= this.maturity) { //reset old boid this.health = 1; birthedBoid = new Boid( this.x + random(-this.personalSpace, this.personalSpace), this.y + random(-this.personalSpace, this.personalSpace) ); birthedBoid.color = this.color; boids.push(birthedBoid); } }, draw: function(ctx) { drawSize = this.size + this.health; ctx.beginPath(); ctx.moveTo(this.x + (this.unitV.x * drawSize), this.y + (this.unitV.y * drawSize)); ctx.lineTo(this.x + (this.unitV.y * drawSize), this.y - (this.unitV.x * drawSize)); ctx.lineTo(this.x - (this.unitV.x * drawSize * 2), this.y - (this.unitV.y * drawSize * 2)); ctx.lineTo(this.x - (this.unitV.y * drawSize), this.y + (this.unitV.x * drawSize)); ctx.lineTo(this.x + (this.unitV.x * drawSize), this.y + (this.unitV.y * drawSize)); ctx.fillStyle = this.color; ctx.shadowBlur = 20; ctx.shadowColor = this.color; ctx.fill(); }};Predator.prototype = new Boid();Predator.prototype.constructor = Predator;Predator.constructor = Boid.prototype.constructor;function Predator(x, y) { this.init(x, y); this.type = "predator"; //body this.maturity = 6; this.speed = 6; this.hungerLimit = 25000; this.color = 'rgb(' + ~~random(100, 250) + ',' + ~~random(10, 30) + ',' + ~~random(10, 30) + ')'; //brains this.eyesight = 150; this.flockDistance = 300;}Predator.prototype.eat = function(other) { if (!this.isFull) { if (other.type === "boid") { other.health--; this.health++; this.isFull = true; this.hunger = 0; } }};Predator.prototype.handleOther = function(other) { if (other.type === "boid") { if (!this.isFull) { this.avoidOrAttract("attract", other); } }};Predator.prototype.mitosis = function(boids) { if (this.health >= this.maturity) { //reset old boid this.health = 1; birthedBoid = new Predator( this.x + random(-this.personalSpace, this.personalSpace), this.y + random(-this.personalSpace, this.personalSpace) ); birthedBoid.color = this.color; boids.push(birthedBoid); }};Plant.prototype = new Boid();Plant.prototype.constructor = Plant;Plant.constructor = Boid.prototype.constructor;function Plant(x, y) { this.init(x, y); this.type = "plant"; //body this.speed = 0; this.size = 10; this.health = ~~random(1, 10); this.color = 'rgb(' + ~~random(130, 210) + ',' + ~~random(40, 140) + ',' + ~~random(160, 220) + ')'; //brains this.eyesight = 0; this.flockDistance = 0; this.eyesight = 0; //range for object dectection this.personalSpace = 100; //distance to avoid safe objects this.flightDistance = 0; //distance to avoid scary objects this.flockDistance = 0; //factor that determines how attracted the boid is to the center of the flock this.matchVelFactor = 0; //factor that determines how much the flock velocity affects the boid}Plant.prototype.ai = function(boids, index, ctx) {};Plant.prototype.move = function() {};Plant.prototype.mitosis = function(boids) { var growProbability = 1, maxPlants = 40, plantCount = 0; for (m = boids.length - 1; m >= 0; m--) { if (boids[m].type === "plant") { plantCount++; } } if (plantCount <= maxPlants) { if (random(0, 100) <= growProbability) { birthedBoid = new Plant( this.x + random(-this.personalSpace, this.personalSpace), this.y + random(-this.personalSpace, this.personalSpace) ); birthedBoid.color = this.color; boids.push(birthedBoid); } }};Plant.prototype.draw = function(ctx) { var drawSize = this.size + this.health; ctx.fillStyle = this.color; ctx.shadowBlur = 40; ctx.shadowColor = this.color; ctx.fillRect(this.x - drawSize, this.y + drawSize, drawSize, drawSize);};/***********************SIM***********************/var boids = [];var sim = Sketch.create({ container: document.getElementById('container')});sim.setup = function() { for (i = 0; i < 50; i++) { x = random(0, sim.width); y = random(0, sim.height); sim.spawn(x, y); }};sim.spawn = function(x, y) { var predatorProbability = 0.1, plantProbability = 0.3; switch (getRandomItem(['boid', 'predator', 'plant'], [1 - predatorProbability - plantProbability, predatorProbability, plantProbability])) { case 'predator': boid = new Predator(x, y); break; case 'plant': boid = new Plant(x, y); break; default: boid = new Boid(x, y); break; } boids.push(boid);};sim.update = function() { for (i = boids.length - 1; i >= 0; i--) { if (boids[i].alive) { boids[i].ai(boids, i, sim); boids[i].move(); boids[i].metabolism(); boids[i].mitosis(boids); } else { //remove dead boid boids.splice(i, 1); } }};sim.draw = function() { sim.globalCompositeOperation = 'lighter'; for (i = boids.length - 1; i >= 0; i--) { boids[i].draw(sim); } sim.fillText(boids.length, 20, 20);};</script></body></html>附：完整实例代码点击此处本站下载。
更多关于JavaScript相关内容感兴趣的读者可查看本站专题：《JavaScript动画特效与技巧汇总》、《JavaScript图形绘制技巧总结》、《JavaScript切换特效与技巧总结》、《JavaScript错误与调试技巧总结》、《JavaScript数据结构与算法技巧总结》及《JavaScript数学运算用法总结》
希望本文所述对大家JavaScript程序设计有所帮助。
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