Drawing a circle using glut...

I can't seem to draw a circle using glut... anybody knows how to do it... thanx in advance. I think i know the logic and that is to split the circle into individual small lines and outputting them...

My original code is this

PHP Code:

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void function(void){
    float calculate (float);

    float x,y;
    int i;
    glClearColor(1.0, 0.0, 1.0, 0.0);    
    glClear(GL_COLOR_BUFFER_BIT);    
    
    
    /*Draw axes*/
    glColor3f(1.0,1.0,1.0);        //black color

    glLineWidth(5); //5 pixels

    /*Perform drawing of axes*/

    glBegin(GL_LINES);
    glVertex2f(0,1);
    glVertex2f(0,-1);

    glVertex2f(1,0);
    glVertex2f(-1,0);

    glEnd();
    
    /*Draw Circle*/
    
    glColor3f(0.0,0.0,1.0);
    glBegin(GL_LINES);
    glLineWidth(3);
    
    for(i=0;i<=500;i++) //no of short lines to be drawn
    {
        x = radius + (i-1)*0.002;
        y= calculate(x);
        /*scale*/
        x= x * 2 - 1;
        y= y * 2 -1;

        glVertex2f(x,y);

        x = radius + i*0.002;
        y= calculate(x);
        x= x * 2 - 1;
        y= y * 2 -1;
        glVertex2f(x,y);
    }
    glEnd();
    glFlush();

}

float calculate(float x)
{
    return radius - x; //pow(x,2) + pow(y,2) = pow(r,2)
                        //y = r - x
} 


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I feel the codes a little weird at the circle area. the axes are all right.

if you want to do it without floating point calculations look into Bressenhams Circle Drawing Algorithm

Code:

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        float x,y;
        float radius = 0.5f;
        glBegin(GL_LINES);
                glColor3f(0.0f,0.0f,0.0f);
               
                x = (float)radius * cos(359 * PI/180.0f);
                y = (float)radius * sin(359 * PI/180.0f);
                for(int j = 0; j < 360; j++)
                {
                        glVertex2f(x,y);
                        x = (float)radius * cos(j * PI/180.0f);
                        y = (float)radius * sin(j * PI/180.0f);
                        glVertex2f(x,y);
                }
        glEnd();

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thanx for the help but there is a another question though. Why is there a 'f' at the end of

Quote:

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float radius = 0.5f

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? Thanx

That is because (at least what I have heard) otherwise the number would default to double and you would (possibly) get a warning. I am not sure though since I dont program in C, I am a C++ guy so I am not too familiar with C standard.

maybe your reasoning is right since double is long float. Thanx anyway