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@HarryStevens
Last active Mar 16, 2018
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Bouncing Balls
license: gpl-3.0

Let people change variables in a system as it updates. Here, you can change the size and speed of the balls.

<!DOCTYPE html>
<html>
<head>
<style>
body {
margin: 0;
font-family: "Helvetica Neue", sans-serif;
}
#sliders {
position: absolute;
background: rgba(255, 255, 255, .8);
padding: 5px;
}
.slider-wrapper {
display: inline-block;
text-align: center;
font-size: .8em;
font-weight: bold;
}
circle {
fill: steelblue;
stroke: white;
}
</style>
</head>
<body>
<div id="canvas">
<div id="sliders">
<div class="slider-wrapper">
<div>Speed</div>
<input data-variable="distance" type="range" id="speed">
</div>
<div class="slider-wrapper">
<div>Size</div>
<input data-variable="radius" type="range" id="size">
</div>
</div>
</div>
<script src="https://d3js.org/d3.v4.min.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<script src="https://unpkg.com/jeezy@1.11.2/lib/jeezy.min.js"></script>
<script>
var width = window.innerWidth, height = window.innerHeight;
var variables = {
radius: 15,
distance: 10
}
var extents = {
radius: [3, 50],
distance: [0, 40]
}
var min = 2, max = 100;
$("#sliders input").each(function(slider_index, slider){
var this_var = $(this).attr("data-variable");
var extent = extents[this_var];
$(this).attr("value", variables[this_var]).attr("min", extent[0]).attr("max", extent[1]);
}).on("change input", function(){
variables[$(this).attr("data-variable")] = $(this).val();
});
var data = [];
var point_count = 20;
var svg = d3.select("#canvas").append("svg").attr("width", width).attr("height", height);
for (var i = 0; i < point_count; i++){
data.push({
id: jz.str.randomString(),
x: jz.num.randBetween(0, width),
y: jz.num.randBetween(0, height),
slope: jz.num.randBetween(1, 20) / 10,
x_dir: [-1, 1][jz.num.randBetween(0, 1)],
y_dir: [-1, 1][jz.num.randBetween(0, 1)]
});
}
redraw(data);
d3.interval(function(){ redraw(update(data)); }, 30)
function redraw(data){
var circle = svg.selectAll("circle")
.data(data, function(d){ return d.id; })
circle
.attr("r", variables.radius)
.attr("cx", function(d){ return d.x; })
.attr("cy", function(d){ return d.y; });
circle.enter().append("circle")
.attr("r", variables.radius)
.attr("cx", function(d){ return d.x; })
.attr("cy", function(d){ return d.y; });
}
function update(data){
data.forEach(function(d){
return calcPointB(d, variables.distance, d.slope);
});
return data;
}
// given a point, p, and a distance, d, and a slope, m, return x and y
// formula from http://www.geeksforgeeks.org/find-points-at-a-given-distance-on-a-line-of-given-slope/
function calcPointB(p, d, m){
p.x_dir = getDir(p.x, p.x_dir, width);
p.y_dir = getDir(p.y, p.y_dir, height);
function getDir(coord, dir, dimension){
return Math.floor(coord) <= variables.radius ? 1 :
Math.ceil(coord) >= dimension - variables.radius ? -1 :
dir;
}
p.x = p.x + (d * Math.sqrt(1 / (1 + Math.pow(m, 2))) * p.x_dir);
p.y = p.y + (m * d * Math.sqrt(1 / (1 + Math.pow(m, 2))) * p.y_dir);
return p;
}
</script>
</body>
</html>
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