JavaScript realizes the animation effect of tadpoles swimming in groups-JS Tutorial-php.cn

This article mainly introduces the JS implementation of the animation effect of simulating the movement of tadpoles swimming in groups based on Sketch.js, involving the use of Sketch.js plug-ins and the application skills of HTML5 elements. It also comes with demo source code for readers to download for reference. It is required Friends can refer to
. This article describes the example of JS implementing the animation effect of tadpoles swimming in groups based on Sketch.js. Share it with everyone for your reference, the details are as follows:
Based on Sketch.js, it implements object touch detection (tadpoles will encounter obstacles and cleverly avoid mouse clicks), random movement, aggregation algorithms, etc.
Already has the basic elements of the game, and it can be turned into a good HTML5 game by extending it.
The demonstration effect is as follows:
The complete code is as follows:
<!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>
<p id="container">
<canvas class="sketch" id="sketch-0" height="208" width="607"></canvas>
</p>
<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 = &#39;rgb(&#39; + ~~random(0, 100) + &#39;,&#39; + ~~random(50, 220) + &#39;,&#39; + ~~random(50, 220) + &#39;)&#39;;
    //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 = &#39;rgb(&#39; + ~~random(100, 250) + &#39;,&#39; + ~~random(10, 30) + &#39;,&#39; + ~~random(10, 30) + &#39;)&#39;;
  //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 = &#39;rgb(&#39; + ~~random(130, 210) + &#39;,&#39; + ~~random(40, 140) + &#39;,&#39; + ~~random(160, 220) + &#39;)&#39;;
  //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(&#39;container&#39;)
});
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([&#39;boid&#39;, &#39;predator&#39;, &#39;plant&#39;], [1 - predatorProbability - plantProbability, predatorProbability, plantProbability])) {
    case &#39;predator&#39;:
      boid = new Predator(x, y);
      break;
    case &#39;plant&#39;:
      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 = &#39;lighter&#39;;
  for (i = boids.length - 1; i >= 0; i--) {
    boids[i].draw(sim);
  }
  sim.fillText(boids.length, 20, 20);
};
</script>
</body>
</html>
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