{
const w = width,
h = width,
context = DOM.context2d(w, h);
const lines = generateKochFractal(context, levels);
for(let line of lines){
line.show();
}
return context.canvas;
}
function generateKochFractal(context, levels) {
let lines = [];
let m = 150;
let ww = width - m - m;
let uu = ww / 4;
lines.push(new KochLine(context, [m + uu * 2, m], [m + uu, m]));
lines.push(new KochLine(context, [m + uu * 3, m + uu], [m + uu * 2, m]));
lines.push(
new KochLine(context, [m + uu * 3, m + uu * 2], [m + uu * 3, m + uu])
);
lines.push(
new KochLine(context, [m + uu * 2, m + uu * 3], [m + uu * 3, m + uu * 2])
);
for (let i = 0; i < levels; i++) {
let next_lines = [];
for (let line of lines) {
const a = line.kochA(),
b = line.kochB(),
c = line.kochC(),
d = line.kochD(),
e = line.kochE();
next_lines.push(new KochLine(context, a, b));
next_lines.push(new KochLine(context, b, c));
next_lines.push(new KochLine(context, c, d));
next_lines.push(new KochLine(context, d, e));
}
lines = next_lines;
}
return lines;
}
class KochLine{
constructor(context, start, end){
this.context = context;
this.start = start;
this.end = end;
}
show(){
this.context.beginPath();
this.context.moveTo(this.start[0], this.start[1]);
this.context.lineTo(this.end[0], this.end[1]);
this.context.stroke();
}
kochA(){
return this.start;
}
kochB(){
let v = [this.end[0] - this.start[0], this.end[1] - this.start[1]];
v = v.map(d => d/3);
return this.start.map((d,i) => d + v[i]);
}
kochC(){
let v = [this.end[0] - this.start[0], this.end[1] - this.start[1]];
v = v.map(d => d/3);
const rotated = this.rotate(v, Math.PI/3);
return this.start.map((d,i) => d + v[i] + rotated[i]);
}
kochD(){
let v = [this.end[0] - this.start[0], this.end[1] - this.start[1]];
v = v.map(d => d/3);
return this.start.map((d,i) => d + 2 * v[i]);
}
kochE(){
return this.end;
}
rotate(vector, angle){
const cos = Math.cos(angle),
sin = Math.sin(angle);
return [vector[0]*cos - vector[1]*sin, vector[0]*sin + vector[1]*cos];
}
}
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