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<!--
This work is licensed under CC BY-NC-ND 4.0
Link to license: http://creativecommons.org/licenses/by-nc-nd/4.0/
Attribute to Russell Georgi
-->
<html>
<head>
<title>
Problem 4-9
</title>
<style>
html, body {
width: 100%;
height: 100%;
margin: 0px;
border: 0;
overflow: hidden;
display: block;
}
canvas {
position: absolute;
}
.dropbtn {
background-color: #04AA6D;
color: white;
padding: 16px;
font-size: 16px;
border: none;
}
.dropdown {
position: absolute;
display: inline-block;
}
.dropdown-content {
display: none;
position: relative;
background-color: #f1f1f1;
box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
z-index: 1;
}
.dropdown-content button {
color: black;
padding: 12px 16px;
width: 100px;
text-decoration: none;
display: block;
}
.dropdown-content a:hover {background-color: #ddd;}
.dropdown:hover .dropdown-content {display: block;}
.dropdown:hover .dropbtn {background-color: #3e8e41;}
</style>
</head>
<body>
<canvas id="myCanvas" width="1" height="1" style="border:1px solid #ffffff;">
Your browser does not support the HTML5 canvas tag.</canvas>
<div class="dropdown">
<button class="dropbtn" id="btn">Mode 1</button>
<div class="dropdown-content">
<button onclick="num(0)">Mode 1</button>
<button onclick="num(1)">Mode 2</button>
</div>
</div>
<script>
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
ctx.canvas.width = window.innerWidth;
ctx.canvas.height = window.innerHeight;
var w = 1;
var amp = 20;
var mode = 0;
var t = 0;
var dt = 0.1;
var xPos = 0;
var yPos = 0;
function num(n)
{
mode = n;
}
ctx.translate(ctx.canvas.width / 2, ctx.canvas.height / 2);
ctx.scale(1.5, 1.5);
function Clear(ctx)
{
ctx.clearRect(-c.width, -c.height, c.width * 2, c.height * 2);
}
function Update()
{
Draw();
t += dt;
setTimeout(Update, 1000/60)
}
function Draw()
{
if (mode == 0)
{
Clear(ctx);
ctx.beginPath();
ctx.arc(xPos + 50 + amp * Math.sin(w * t), yPos, 5, 0, Math.PI * 2);
ctx.fill();
ctx.beginPath();
ctx.arc(xPos - 50 + amp * (Math.sqrt(3) - 1) * Math.sin(w * t) / 2, yPos, 5 * Math.sqrt(2), 0, Math.PI * 2);
ctx.fill();
drawSpring(1, 3, 100 + amp * (Math.sqrt(3) - 1) * Math.sin(w * t) / 2, 10, 5, xPos - 150, yPos, 0.1, 0);
drawSpring(1, 3, 100 - amp * (Math.sqrt(3) - 1) * Math.sin(w * t) / 2+ amp * Math.sin(w * t), 10, 5, xPos - 50 + amp * (Math.sqrt(3) - 1) * Math.sin(w * t) / 2, yPos, 0.1, 0);
drawSpring(1, 3, 100 - amp * Math.sin(w * t) , 10, 5, xPos + 50 + amp * Math.sin(w * t), yPos, 0.1, 0);
} else if (mode == 1)
{
Clear(ctx);
ctx.beginPath();
ctx.arc(xPos + 50 + amp * Math.sin(w * t), yPos, 5, 0, Math.PI * 2);
ctx.fill();
ctx.beginPath();
ctx.arc(xPos - 50 + amp * (-Math.sqrt(3) - 1) * Math.sin(w * t) / 2, yPos, 5 * Math.sqrt(2), 0, Math.PI * 2);
ctx.fill();
drawSpring(1, 3, 100 + amp * (-Math.sqrt(3) - 1) * Math.sin(w * t) / 2, 10, 5, xPos - 150, yPos, 0.1, 0);
drawSpring(1, 3, 100 - amp * (-Math.sqrt(3) - 1) * Math.sin(w * t) / 2+ amp * Math.sin(w * t), 10, 5, xPos - 50 + amp * (-Math.sqrt(3) - 1) * Math.sin(w * t) / 2, yPos, 0.1, 0);
drawSpring(1, 3, 100 - amp * Math.sin(w * t) , 10, 5, xPos + 50 + amp * Math.sin(w * t), yPos, 0.1, 0);
}
}
function drawSpring(a, b, xSize, ySize, numLoops, x, y, tStep, deltaY)
{
var tStart = Math.PI / 2;
var tEnd = (3 * Math.PI / 2) + (2 * Math.PI * numLoops);
var xEnd = a * tEnd - b * Math.sin(tEnd);
var yEnd = a + b;
var xFactor = xSize / xEnd;
var yFactor = ySize / yEnd;
var xShift = x - a * (Math.PI / 2) + b * Math.sin(Math.PI / 2);
var yShift = y - a + b * Math.cos(Math.PI / 2);
var slope = deltaY / xSize;
for (p = tStart; p <= tEnd; p += tStep)
{
ctx.beginPath();
ctx.moveTo(xShift + xFactor * (a * p - b * Math.sin(p)), yShift + yFactor * (a - b * Math.cos(p)) + slope * (a * p - b * Math.sin(p)));
ctx.lineTo(xShift + xFactor * (a * (p + tStep) - b * Math.sin(p + tStep)), yShift + yFactor * (a - b * Math.cos(p + tStep)));
ctx.stroke();
}
}
window.addEventListener('resize', function(event) {
c.width = window.innerWidth;
c.height = window.innerHeight;
ctx.translate(c.width / 2, c.height / 2);
ctx.scale(1.5, 1.5);
}, true);
Update();
</script>
</body>
<p xmlns:cc="http://creativecommons.org/ns#" style="font-size: 1vw; bottom: 0px; position: absolute;">
This work is licensed under
<a href="http://creativecommons.org/licenses/by-nc-nd/4.0/?ref=chooser-v1" target="_blank" rel="license noopener noreferrer" style="display:inline-block;">CC BY-NC-ND 4.0<img style="height:22px!important;margin-left:3px;vertical-align:text-bottom;" src="https://mirrors.creativecommons.org/presskit/icons/cc.svg?ref=chooser-v1"><img style="height:22px!important;margin-left:3px;vertical-align:text-bottom;" src="https://mirrors.creativecommons.org/presskit/icons/by.svg?ref=chooser-v1"><img style="height:22px!important;margin-left:3px;vertical-align:text-bottom;" src="https://mirrors.creativecommons.org/presskit/icons/nc.svg?ref=chooser-v1"><img style="height:22px!important;margin-left:3px;vertical-align:text-bottom;" src="https://mirrors.creativecommons.org/presskit/icons/nd.svg?ref=chooser-v1"></a></p>
</html>