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OpenGL How do I draw a circle using OpenGL?

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Hi there! I would like to know how do I draw a circle using OpenGL. Thanks in advance!

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Let rad be the radius of the n-gon and c the number of sides then.

float ad=(float)(2.0f*PI)/(float)c;
float a=0;
for (int i=0;i<c;i++;a+=ad;)
{
xOfNewPoint=cos(a)*rad;
yOfNewPoint=sin(a)*rad;
}

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That's not legal C, CableGuy. You need to have a comma separating the i++ and the a+=ad. Not to mention, you could use much more descriptive variable names:


int numSides = whateverYouWant;
float currentAngle = 0.0f;
float deltaAngle= 2.0f*PI / float(numSides); //Difference between each point

glBegin(GL_POLYGON);


for( int i = 0; i < numSides; i++ )//Could just have incremented currentAngle until it was >= 2*PI, but this works too
{
currentAngle += deltaAngle; //I like this better in here than in the for(). Just aesthetics

//Gives the Polygon a new vertex
glVertex2f( cos(currentAngle), sin(currentAngle) );
}

glEnd();

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Yeah at first the currentAngle += deltaAngle; was in the for loop but then
I moved it to the for line don't know why, because of that I did the ;, mistake.

And yeah I just copied the code from some old 2d simulator. So the variables' names are a bit hacky.

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