var c=document.getElementById("c"),e=c.getContext("2d"),g=Math.cos,i=Math.sin;c.width=innerWidth;c.height=innerHeight;var j=c.width/2,k=c.height/2,l=[],m=0,n=0;c.onmousemove=function(d){m=d.clientX;n=d.clientY};(c.onclick=function(d){l=[];d=new Function("x,y","return "+(d?prompt("function","Math.PI*Math.sin(Math.sqrt(x*x+y*y))/Math.sqrt(x*x+y*y)"):"Math.PI*Math.sin(Math.sqrt(x*x+y*y))/Math.sqrt(x*x+y*y)"));for(var f=-10;f<10;f+=0.5)for(var a=-10;a<10;a+=0.5)l.push({x:f*10,y:a*10,a:20*d(f,a)})})();
setInterval(function(){var d=1.0E-4*(m-j),f=g(d);d=i(d);var a=1.0E-4*(n-k),o=g(a),p=i(a),b,h;for(a=l.length;a--;){b=l[a];h=b.a*f+b.x*d;b.x=b.x*f-b.a*d;b.a=h*o+b.y*p;b.y=b.y*o-h*p;h=200/(200+b.a);b.b=j+b.x*h;b.c=k+b.y*h}e.clearRect(0,0,c.width,c.height);if(l.length){e.strokeStyle="rgb(40,50,20)";e.beginPath();e.moveTo(l[0].b,l[0].c);f=l.length;for(a=1;a<f;a++)try{a%40?e.lineTo(l[a].b,l[a].c):e.moveTo(l[a].b,l[a].c)}catch(q){}e.stroke()}e.fillText("Click to edit equation",99,99)},0);
var b = document.body, c = document.getElementById("c"), t = c.getContext("2d"), cos = Math.cos, sin = Math.sin;
b.style.margin = 0;
c.width = innerWidth;
c.height = innerHeight;
var f = 200,
vpX = c.width / 2,
vpY = c.height / 2,
p = [];
var mX = 0, mY = 0;
c.onmousemove = function(e){
mX = e.clientX;
mY = e.clientY;
}
;(c.onclick = function(eq){
p = [];
var def = 'Math.PI*Math.sin(Math.sqrt(x*x+y*y))/Math.sqrt(x*x+y*y)';
var fn = new Function('x,y','return '+(eq?prompt('function',def):def));
for(var x = -10; x < 10; x+=.5){
for(var y = -10; y < 10; y+=.5){
p.push({
x: x*10,
y: y*10,
z: 20*fn(x,y)
})
}
}
})();
setInterval(function(){
var aY = 1e-4 * (mX - vpX),
cY = cos(aY),
sY = sin(aY),
aX = 1e-4 * (mY - vpY),
cX = cos(aX),
sX = sin(aX),
point, S, z1;
for(var i = p.length; i--;) {
point = p[i];
z1 = point.z * cY + point.x * sY;
point.x = point.x * cY - point.z * sY;
point.z = z1 * cX + point.y * sX;
point.y = point.y * cX - z1 * sX;
S = f / (f + point.z);
point._x = vpX + point.x * S;
point._y = vpY + point.y * S
}
t.clearRect(0, 0, c.width, c.height);
if(p.length){
t.strokeStyle = "rgb(40,50,20)";
t.beginPath();
t.moveTo(p[0]._x, p[0]._y);
for(var l = p.length,i=1;i<l;i++){
try{
if(i % 40)
t.lineTo(p[i]._x, p[i]._y);
else t.moveTo(p[i]._x, p[i]._y);
}catch(e){} //sometimes p[i]._x == NaN
}
t.stroke()
}
t.fillText('Click to edit equation',99,99)
},0);
