30 lines
766 B
JavaScript
30 lines
766 B
JavaScript
var ctx = document.getElementById('tutorial').getContext('2d');
|
|
ctx.fillRect(0,0,300,300);
|
|
for (var i=0;i<3;i++) {
|
|
for (var j=0;j<3;j++) {
|
|
ctx.save();
|
|
ctx.strokeStyle = "#9CFF00";
|
|
ctx.translate(50+j*100,50+i*100);
|
|
drawSpirograph(ctx,20*(j+2)/(j+1),-8*(i+3)/(i+1),10);
|
|
ctx.restore();
|
|
}
|
|
}
|
|
|
|
function drawSpirograph(ctx,R,r,O){
|
|
var x1 = R-O;
|
|
var y1 = 0;
|
|
var i = 1;
|
|
ctx.beginPath();
|
|
ctx.moveTo(x1,y1);
|
|
do {
|
|
if (i>20000) break;
|
|
var x2 = (R+r)*Math.cos(i*Math.PI/72) - (r+O)*Math.cos(((R+r)/r)*(i*Math.PI/72))
|
|
var y2 = (R+r)*Math.sin(i*Math.PI/72) - (r+O)*Math.sin(((R+r)/r)*(i*Math.PI/72))
|
|
ctx.lineTo(x2,y2);
|
|
x1 = x2;
|
|
y1 = y2;
|
|
i++;
|
|
} while (x2 != R-O && y2 != 0 );
|
|
ctx.stroke();
|
|
}
|