困难是动摇者和懦夫掉队回头的便桥；但也是勇敢者前进的脚踏石。我不识何谓君子，但看每事肯吃亏者便是；我不识何谓小人，但看每事好占便宜者便是。
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。
希望本文所述对大家JavaScript程序设计有所帮助。
本文JS实现基于Sketch.js模拟成群游动的蝌蚪运动动画效果【附demo源码下载】到此结束。我相信，所有的梦想，都是一个充满责任成功的人生，当你还没有条件去自由的选择，请记住，梦想在我们的下一步，做好每一件小事，做得与众不同，我们就会向梦想走近。小编再次感谢大家对我们的支持！
