Khan Academy项目：applyForce函数报错与Buglight发光异常求助

嘿，我来帮你搞定这两个问题！咱们一个一个来拆解：

问题1：applyForce is not a function 报错 #

这个问题很直接——你的Mover类根本没定义applyForce方法，调用的时候自然会抛出错误。咱们需要给Mover原型添加这个方法，按照牛顿第二定律F=ma，把传入的力除以物体质量后，加到加速度上即可：

Mover.prototype.applyForce = function(force) {
  // 根据质量计算加速度（F=ma → a=F/m）
  var f = PVector.div(force, this.mass);
  this.acceleration.add(f);
};

问题2：Buglight的glow值变化过快，仅显示最大发光量 #

目前你的Buglight没有控制发光量渐变的逻辑，直接赋值当然会跳变。咱们可以给Buglight加一个glowSpeed属性来控制变化速率，然后在update方法里逐步调整glow的值，同时设置上下边界，达到边界时反转速度，实现平滑的呼吸效果：

修改Buglight的构造函数 #

给Buglight添加glowSpeed属性（数值可以根据需求调整，越小变化越慢）：

var Buglight = function (){
  this.position = new PVector (random(width-50),random(height-80));
  this.velocity = new PVector (0,0);
  this.acceleration = new PVector (0,0);
  this.glow = 70;
  this.mass = 20;
  this.G = 1;
  this.glowSpeed = 1; // 新增：控制发光量变化速率
};

修改Buglight的update方法 #

在update里处理glow的渐变逻辑：

Buglight.prototype.update = function() {
  // 逐步调整发光量
  this.glow += this.glowSpeed;
  // 设置发光量的上下限（这里设为50-100，你可以自己修改范围）
  if (this.glow > 100 || this.glow < 50) {
    this.glowSpeed *= -1; // 达到边界时反转方向
  }
  // 绘制发光效果
  noStroke();
  fill(39, 131, 207,90);
  ellipse(this.position.x+20,this.position.y+35,this.glow,this.glow);
};

完整修改后的代码 #

var Mover = function() {
  this.position = new PVector (random(width),random(height));
  this.velocity = new PVector (0,0);
  this.acceleration = new PVector (0,0);
  this.mass = 1;
};

Mover.prototype.applyForce = function(force) {
  var f = PVector.div(force, this.mass);
  this.acceleration.add(f);
};

Mover.prototype.update = function () {
  var mouse = new PVector(mouseX,mouseY);
  var dist = PVector.sub(mouse, this.position);
  var randomPush = new PVector(random(-1,1),random(-1,1));
  dist.normalize();
  dist.mult(0.4);
  this.acceleration = dist;
  this.acceleration.add(randomPush);
  this.velocity.add(this.acceleration);
  this.velocity.limit(9);
  this.position.add(this.velocity);
};

Mover.prototype.display = function () {
  strokeWeight(7);
  stroke(0, 0, 0);
  point(this.position.x,this.position.y);
  strokeWeight(5);
  point(this.position.x - 3,this.position.y -3);
  point(this.position.x + 3,this.position.y -3);
};

var Buglight = function (){
  this.position = new PVector (random(width-50),random(height-80));
  this.velocity = new PVector (0,0);
  this.acceleration = new PVector (0,0);
  this.glow = 70;
  this.mass = 20;
  this.G = 1;
  this.glowSpeed = 1;
};

Buglight.prototype.update = function() {
  this.glow += this.glowSpeed;
  if (this.glow > 100 || this.glow < 50) {
    this.glowSpeed *= -1;
  }
  noStroke();
  fill(39, 131, 207,90);
  ellipse(this.position.x+20,this.position.y+35,this.glow,this.glow);
};

Buglight.prototype.repulsion = function(fly) {
  var force = PVector.sub(this.position,fly.position);
  var distance = force.mag();
  distance = constrain(distance, 4.0, 20.0);
  force.normalize();
  var strength = -1 *(this.G * this.mass * fly.mass) / (distance * distance);
  force.mult(strength);
  return force;
};

Buglight.prototype.display = function() {
  noStroke();
  fill(5, 170, 252);
  rect(this.position.x+15,this.position.y,10,60);
  fill(0, 0, 0);
  noStroke();
  rect(this.position.x-10,this.position.y+60,60,10,10);
  rect(this.position.x,this.position.y,10,60);
  rect(this.position.x+30,this.position.y,10,60 );
  quad(this.position.x,this.position.y,
       this.position.x-10,this.position.y+20,
       this.position.x+50,this.position.y+20,
       this.position.x+40,this.position.y);
};

Buglight.prototype.checkEdges = function () {
};

var flies = [];
for (var i = 0; i < 4; i++){
  flies[i] = new Mover();
}

var buglight = new Buglight();
var fly = new Mover();

draw = function() {
  background(71, 71, 71);
  strokeWeight(56);
  stroke(219, 247, 8,100);
  fill(255, 238, 0);
  ellipse(mouseX,mouseY,20,20);
  
  buglight.update();
  buglight.display();
  
  for (var j = 0; j < flies.length; j++) {
    var blueForce = buglight.repulsion(flies[j]);
    flies[j].applyForce(blueForce);
    flies[j].update();
    flies[j].display();
  }
};

内容的提问来源于stack exchange，提问作者jj1993