I was wondering how you would draw a 2d circle in openGL since there is no built in function to do it. I want to be able to specify a radius, I''ve seen some examples that draw a fixed size circle, but none able to specify a radius. I want something like DrawCircle(double radius) { glBegin(GL_POLYGON) for(...) { //..... } glEnd(); }

for (i=0;i<360;i++)
{
x = radius_x * cos(i*3.14/180);
y = radius_y * sin(i*3.14/180);
DrawPixel(x,y);
}

I don''t remember exactly, but I think it''s the correct way.

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Flamewars don''t make you look smart, but idiot.

quote:

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Original post by Pontius
I was wondering how you would draw a 2d circle in openGL since there is no built in function to do it. I want to be able to specify a radius, I've seen some examples that draw a fixed size circle, but none able to specify a radius. I want something like

DrawCircle(double radius)
{

glBegin(GL_POLYGON)
for(...)
{
//.....
}
glEnd();
}

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you can your glu functions ...

GLUquadricObj *Circle;
Circle = gluNewQuadric ();

gluDisk (Circle,innerRadius,outerRadius,slices,loops) ;
...
here is the definition of gluDisk :

then use gluDeleteQuadric to destroy the object




[edited by - Metal Typhoon on January 6, 2003 7:18:30 PM]

if you want to alter the resolution of the circle, change i++ to i+=2 for half the resolution, or i+=6 for a point every 30 degrees, using this you can create regular polygons in one easy fuunction.

"Very funny, Scotty. Now beam down my clothes."

Thanks, here it is, this works fine if anyone needs it


void DrawCircle(double Radius, int Edges)
{
GLfloat x, y, temp;
glBegin(GL_POLYGON);
temp = 360.0 / (float)Edges;
for(float i = 0; i < 360; i+=temp)
{
x = Radius * cos(i * PI / 180.0f);
y = Radius * sin(i * PI / 180.0f);

glVertex2f(x, y);
}
glEnd();
}