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# drawing a 2D torus (basically a circle with a hole in it).

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3 replies to this topic

### #1Enerjak  Members

Posted 17 March 2013 - 12:15 AM

I've been trying to render a torus (in 2D) in OpenGL and Well, I think I'm on the right track but I thought I'd ask you how to go about getting it to work. here's the code:

// attempting to create a torus (in 2D)
int numSegments,
double x,
double y)
{
double mAngle = 0.0;
double mAngle2 = 0.0;
glBegin(GL_POLYGON);
for(int i = 0; i < numSegments; i++)
{
mAngle = i * (2 * 3.14/numSegments);
mAngle2 = i * (2 * 3.14/numSegments);
}

glEnd();
}


now here's the polygon this produces:

http://puu.sh/2j6uh

please let me know if there's anything I need to do to fix this.

### #2Dragonsoulj  Members

Posted 17 March 2013 - 05:55 AM

Looks like you are on the right track for the ring. Does increasing your number of segments give you a smoother looking ring?

### #3C0lumbo  Members

Posted 17 March 2013 - 06:49 AM

The shape you're trying to draw is not a convex polygon, so using GL_POLYGON is wrong. I think GL_TRIANGLE_STRIP is a better fit. In switching to a triangle strip you should change the 'for' condition to <=.

### #4Enerjak  Members

Posted 17 March 2013 - 09:40 AM

thanks, I can always count on the fine people on this forum!

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