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I'm trying to draw a circle using simple vertices points and a big gl_PointSize value. I found this example and try to reproduce it on WebGL with no success.

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closed as not a real question by Nicol Bolas, msell, Anko, bummzack, Sean Middleditch May 29 '13 at 23:49

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We need more information. What goes wrong? What did you try? –  olevegard May 16 '13 at 9:17
    
Here is an example codepen.io/moechofe/pen/ezgFb It seems my problem is my program doesn't compile when I add the varying variable. –  moechofe May 16 '13 at 18:37
    
I forgot to add "precision mediump float;" in my fragment shader –  moechofe May 16 '13 at 18:44
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1 Answer 1

This is just using regular old sine and cosine to step around the circumference of a circle and place points. You just need to know the center of the circle, the radius and how many points you want. The following pseudo code will output a set of points that make up the positions of dots you need to make a circle of points:

circleXY(Vector3f center, float radius, int dots) {
    float stepSize = ((2*Math.PI)/dots);
    for (float d = 0; d <= (2*Math.PI)-stepSize; d += stepSize) {
      addPoint(((sin(d) * radius) + center.x),
                (cos(d) * radius) + center.y));
    }
    return result;
}

You will have to modify it to fit your language and APIs. But, if you know how to draw a point, you can easily utilize this to know where to draw them.

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