眼睛跟随光标 - 定位？

Question

我正在尝试使用 Javascript 创建一个跟随鼠标在页面周围移动的东西。我希望它是米老鼠，我希望他的眼睛跟随鼠标在他的眼球周围移动......这是我迄今为止所拥有的代码（从网络上的各个地方收集，所以感谢写了什么部分的人）：

<script>
var jseyesimg="http://oi67.tinypic.com/frnys.jpg";
var jseyeimg="http://oi63.tinypic.com/nxwa5u.jpg";
var jseyeslink="http://www.javascriptkit.com";

var jseyeso=null, jseye1=null, jseye2=null;
var standardbody=(document.compatMode=="CSS1Compat")? document.documentElement : document.body //create reference to common "body" across doctypes

function jseyesobj(id) {
var i, x;
x= document[id];
if (!x && document.getElementById) x= document.getElementById(id);
for (i=0; !x && i<document.forms.length; i++) x= document.forms[i][id];
return(x);
}

function jseyesmove(x, y) {
var ex, ey, dx, dy;
if (jseyeso && jseye1 && jseye2 && jseyeso.style) {
ex=jseyeso.offsetLeft+46; ey=jseyeso.offsetTop+58;
dx=x-ex; dy=y-ey;
r=(dx*dx/49+dy*dy/289<1) ? 1 : Math.sqrt(49*289/(dx*dx*289+dy*dy*49));
jseye1.style.left= r*dx+36.5+'px'; jseye1.style.top= r*dy+44+'px';
ex+=56; dx-=56;
r=(dx*dx/49+dy*dy/289<1) ? 1 : Math.sqrt(49*289/(dx*dx*289+dy*dy*49));
jseye2.style.left= r*dx+92.5+'px'; jseye2.style.top= r*dy+44+'px';
}
}

function jseyes() {
var img;
var x, y, a=false;

if (arguments.length==2) {
x= arguments[0];
y= arguments[1];
a= true;
}

img= "<div id='jseyeslayer' style='position:"+
       (a ? "absolute; left:"+x+"; top:"+y : "relative")+
       "; z-index:5; width:150; height:150 overflow:hidden'>"+
     "<div id='jseye1' style='position:absolute; left:130; top:44; z-index:6; width:21; height:29'>"+
       "<img src='"+jseyeimg+"' width=21 height=29 onClick=\"location.href='"+jseyeslink+"'\">"+
     "</div>"+
     "<div id='jseye2' style='position:absolute; left:160; top:44; z-index:6; width:21; height:29'>"+
       "<img src='"+jseyeimg+"' width=21 height=29 onClick=\"location.href='"+jseyeslink+"'\">"+
     "</div>"+
     "<img src='"+jseyesimg+"' width=300 height=300 onClick=\"location.href='"+jseyeslink+"'\">"+
 "</div>";
document.write(img);
jseyeso=jseyesobj('jseyeslayer');
jseye1=jseyesobj('jseye1');
jseye2=jseyesobj('jseye2');

document.onmousemove=jseyesmousemove;
}

function jseyesmousemove(e) {
    var mousex=(e)? e.pageX : event.clientX+standardbody.scrollLeft
    var mousey=(e)? e.pageY : event.clientY+standardbody.scrollTop
jseyesmove(mousex, mousey);
//return(false);
}
</script>

我不知道如何将眼睛放在眼球内。如果有人能告诉我什么值意味着什么，我想尝试一些数字来看看什么看起来最好。 :)

谢谢:)

Answer 1

我个人认为用画布来做这样的事情更有意义。

我在下面创建了一个带注释的示例。该示例不使用图像，因此您必须自己完成该部分，这是一个很好的关于 canvas API 信息的资源（包括如何绘制图像）can be found on MDN。

数学可以分解为：

1. 计算鼠标与眼球中心的夹角
2. 使用三角法在该角度找到眼睛圆周上的点。由于米奇的眼睛是椭圆而不是完美的圆形，因此数学非常复杂，因此它们的半径会根据角度而变化。 See this answer 了解更多详情。
3. 减去瞳孔半径（再次使用点 2 的三角函数，因为半径会根据角度而变化）。

注意：按“运行代码 sn-p”查看示例工作。

const canvas = document.querySelector('canvas');
const context = canvas.getContext('2d');
const TWOPI = 2 * Math.PI;

// size the canvas to the full width/height available
// Note: this solution is not responsive
canvas.width = innerWidth;
canvas.height = innerHeight;

// eye objects will be in charge of holding state and rendering themselves
class Eye {
  constructor(x, y) {
    this.x = x;
    this.y = y;
    this.width = 40;
    this.height = 80;
    this.pupil = { x: 0, y: 0, width: 10, height: 20 };
  }

  draw() {
    const {x, y} = this;
    
    context.save();
    context.translate(x, y);
    
    this.drawOutline();
    this.drawPupil()
    
    context.restore();
  }
  
  drawOutline() {
    const {width, height} = this;
    
    context.beginPath();
    context.ellipse(0, 0, width, height, 0, 0, TWOPI);
    context.stroke();
  }
  
  drawPupil() {
    const {x, y, width, height} = this.pupil;
    
    context.beginPath();
    context.ellipse(x, y, width, height, 0, 0, TWOPI);
    context.fill();
  }
  
  track(object) {
    const {x, y, width, height, pupil} = this;
    // find the angle between the mouse and the center of the eye
    const xDiff = (x - object.x);  
    const yDiff = (y - object.y);
    const angle = Math.atan2(yDiff, xDiff) - Math.PI;

    if (!isNaN(angle)) {
      // calculate the point on the circumference of the eye
      const cX = (width * Math.cos(angle));
      const cY = (height * Math.sin(angle));
      // calculate the point on the circumference of the pupil
      const pX = pupil.width * Math.cos(angle);
      const pY = pupil.height * Math.sin(angle);
    
      //  position the pupil at the edge of the eye, minus the radius of the pupil
      pupil.x = cX - pX;
      pupil.y = cY - pY;
    }
  }
}

// on mousemove update the mouse position
window.addEventListener('mousemove', e => {
  mouse.x = e.clientX;
  mouse.y = e.clientY;
});

const mouse = { x: 0, y: 0 };
const leftEye = new Eye(100, 100);
const rightEye = new Eye(200, 100);

// on every tick redraw the eyes with a new position
function tick() {
  // clear canvas
  context.clearRect(0, 0, canvas.width, canvas.height);
  
  // track the mouse and draw the left eye
  leftEye.track(mouse);
  leftEye.draw();
  
  // copy the state of the left eyes pupil
  rightEye.pupil.x = leftEye.pupil.x;
  rightEye.pupil.y = leftEye.pupil.y;
  //rightEye.track(mouse); // or use this for independent eye tracking
  rightEye.draw();
 
  requestAnimationFrame(tick);
}

// kick off animation loop
tick();

body { margin: 0; }

<canvas />

如果您对可视化编程感兴趣，我认为您可以通过查看 p5.js 和 work of Daniel Shiffman 来学到很多东西；他有很多关于像这样的东西入门的视频。我希望这会有所帮助，祝你好运！