效果展示
下面两个效果是在同一个页面中出现的，为了便于观察，因为分为了两部分来展示。
这是锁定时产生的主体效果：
这是定位产生的效果（将位于页面左下角展示，也已在其他位置展示）
代码
index.html
<!DOCTYPE html>
<html lang="en" >
<head>
<meta charset="UTF-8">
<title>追光者♂</title>
<link rel='stylesheet' href='https://fonts.googleapis.com/css?family=Abel'>
<link rel="stylesheet" href="css/style.css">
</head>
<body>
<canvas id="myCanvas"></canvas>
<div class="info">
<h1>Boss, CODING Please.</h1>
<p class="message">temp</p>
</div>
<script src='https://cdnjs.cloudflare.com/ajax/libs/jquery/3.1.1/jquery.min.js'></script>
<script src="js/index.js"></script>
</body>
</html>
index.js
var c = $("#myCanvas")[0];
var ctx = c.getContext("2d");
var color_gold="185,147,98";
var ww,wh;
var center={
x: 0,y: 0};
function getWindowSize(){
ww=$(window).outerWidth();
wh=$(window).outerHeight();
c.width=ww;
c.height=wh;
center={
x: ww/2,y: wh/2};
ctx.restore();
ctx.translate(center.x,center.y);
}
getWindowSize();
$(window).resize(getWindowSize);
var enemies=Array(10).fill({
}).map(
function(obj){
return {
r: Math.random()*200,
deg: Math.random()*360,
opacity: 0
}
}
);
setInterval(draw,10);
var time=0;
var deg_to_pi=Math.PI/180;
function Point(r,deg){
return {
x: r*Math.cos(deg_to_pi*deg),
y: r*Math.sin(deg_to_pi*deg),
};
}
function Color(op){
return "rgba("+color_gold+","+op+")";
}
function draw(){
time+=1;
ctx.fillStyle = "#111";
ctx.beginPath();
ctx.rect(-2000,-2000,4000,4000);
ctx.fill();
ctx.strokeStyle="rgba(255,255,255,0.1)";
ctx.moveTo(-ww/2,0);
ctx.lineTo(ww/2,0);
ctx.moveTo(0,-wh/2);
ctx.lineTo(0,wh/2);
ctx.stroke();
ctx.strokeStyle=Color(1);
var r=200;
var deg=time;
var newpoint=Point(r,deg);
var line_deg = (time/2) % 360;
var line_deg_len=100;
for(var i=0;i<line_deg_len;i++){
// var deg = (time-i);
var deg1 = (line_deg-i-1) ;
var deg2 = (line_deg-i) ;
var point1=Point(r,deg1);
var point2=Point(r,deg2);
var opacity=1-(i/line_deg_len)-0.3;
if (i==0) opacity=1;
ctx.beginPath();
ctx.fillStyle=Color(opacity);
ctx.moveTo(0,0);
ctx.lineTo(point1.x,point1.y);
ctx.lineTo(point2.x,point2.y);
ctx.fill();
}
enemies.forEach(function(obj){
ctx.fillStyle=Color(obj.opacity);
var obj_point=Point(obj.r,obj.deg);
ctx.beginPath();
ctx.arc(
obj_point.x,obj_point.y,
4,0,2*Math.PI
);
ctx.fill();
ctx.strokeStyle= Color(obj.opacity);
var x_size=6;
ctx.lineWidth=4;
ctx.beginPath();
ctx.moveTo(obj_point.x-x_size,obj_point.y+x_size);
ctx.lineTo(obj_point.x+x_size,obj_point.y-x_size);
ctx.moveTo(obj_point.x+x_size,obj_point.y+x_size);
ctx.lineTo(obj_point.x-x_size,obj_point.y-x_size);
ctx.stroke();
if (Math.abs(obj.deg - line_deg)<=1){
obj.opacity=1;
$(".message").text("Detected: "+ obj.r.toFixed(3) + " at " +obj.deg.toFixed(3));
}
obj.opacity*=0.99;
ctx.strokeStyle= Color(obj.opacity);
ctx.lineWidth=1;
ctx.beginPath();
ctx.arc(
obj_point.x,obj_point.y,
10*(1/(obj.opacity+0.0001)),0,2*Math.PI
);
ctx.stroke();
});
ctx.strokeStyle=Color(1);
var split =120;
var feature =15;
var start_r=230;
var len = 5;
for(var i=0;i<split;i++){
ctx.beginPath();
var deg = (i/120) * 360;
if (i%feature==0){
len=10;
ctx.lineWidth=3;
}else{
len=5;
ctx.lineWidth=1;
}
var point1 =Point(start_r,deg);
var point2 =Point(start_r+len,deg);
ctx.moveTo(point1.x,point1.y);
ctx.lineTo(point2.x,point2.y);
ctx.stroke();
}
function CondCircle(r,lineWidth,func_cond){
ctx.lineWidth=lineWidth;
ctx.strokeStyle=Color(1);
ctx.beginPath();
for(var i=0;i<=360;i++){
var point =Point(r,i);
if (func_cond(i)){
ctx.lineTo(point.x,point.y);
}else{
ctx.moveTo(point.x,point.y);
}
}
ctx.stroke();
}
CondCircle(300,2,function(deg){
return ((deg+time/10)%180)<90;
});
CondCircle(100,1,function(deg){
return (deg%3)<1;
});
CondCircle(190,1,function(deg){
return true;
});
}
style.css
html, body {
width: 100%;
height: 100%;
padding: 0;
margin: 0;
overflow: hidden;
font-family: Abel;
}
canvas {
background-color: #333;
-webkit-transform: scaleY(-1);
transform: scaleY(-1);
}
.info {
position: absolute;
left: 50px;
bottom: 50px;
}
h1 {
color: white;
letter-spacing: 3px;
margin: 0;
}
.message {
margin: 0;
color: #b99362;
}
另外，为了便于大家查看，我也将这个特效的源文件上传到了“资源”中，喜欢的朋友可以去下载哦！