CODEWITHSUNDEEP
javascriptmathrotation2d
user1735714
user1735714

Reputation: 31

2d rotation 1000 random points around one point

I generate 1000 random points, and I'd like to rotate the points, around some point defined by x and y.

I've used:

px = Math.cos(theta) * (px-ox) - Math.sin(theta) * (py-oy) + ox

py = Math.sin(theta) * (px-ox) + Math.cos(theta) * (py-oy) + oy

but the problem is that points start to converge, to rotation point after rotating for some time.

Here is the javascript code. http://www.kaotik.si/rotation1.html

what I am doing wrong ?

the iteration section of code:

for (var i = 0; i < tocke.length; i++) 
{
    px = tocke[i]["x"];
    py = tocke[i]["y"];
    r = tocke[i]["r"];
    g = tocke[i]["g"];
    b = tocke[i]["b"];

    theta = 0.1;
    ox = centerX;
    oy = centerY;
    px = Math.cos(theta) * (px-ox) - Math.sin(theta) * (py-oy) + ox
    py = Math.sin(theta) * (px-ox) + Math.cos(theta) * (py-oy) + oy
    tocke[i]["x"] = px;
    tocke[i]["y"] = py;

    draw_point(px,py,r,g,b,1);
}

Edit: Thanks for solving the problem: I did have to change to:

theta = 0.1;
ox = centerX;
oy = centerY;
tmpX = Math.cos(theta) * (px-ox) - Math.sin(theta) * (py-oy) + ox
tmpY = Math.sin(theta) * (px-ox) + Math.cos(theta) * (py-oy) + oy
tocke[i]["x"] = tmpX;
tocke[i]["y"] = tmpY;
draw_point(px,py,r,g,b,1);

Upvotes: 0

Views: 749

Answers (1)

Oliver Charlesworth
Oliver Charlesworth

Reputation: 272507

You're reassigning px before it gets used in the calculation for py.

Upvotes: 4

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