Bresenham Circle Algorithm

Does anyone have experience with this algo.. i can't seem to get it working right (i converted the code i found on gamedev from pascal to c++)?

Code:

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PHP Code:

       

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    int d,mx,my;

    d = 3 - (2*radius);
    mx = 0;
    my = radius;

    while(my != mx)
    {
        DrawPixel(surface,x+mx,y+my,color);
        DrawPixel(surface,x+mx,y-my,color);
        DrawPixel(surface,x-mx,y+my,color);
        DrawPixel(surface,x-mx,y-my,color);
        DrawPixel(surface,x+my,y+mx,color);
        DrawPixel(surface,x+my,y-mx,color);
        DrawPixel(surface,x-my,y+mx,color);
        DrawPixel(surface,x-my,y-mx,color);

        if(d < 0)
            d += (4*mx)+6;    
        else
        {
            d += 4*(mx-my) + 10;
            my--;
        }
    } 




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edit: It is drawing a + sign rather than an O.. I'm trying to figure this one out but so far no luck.

I don't remember if it was Bresenham's or another one, but I got it to work with DirectDraw. I'll try and find it.

Here's the algorithm I used: (it's almost actual code so you should be able to modify it to what you need)

Code:

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int x_center;  // the center of the circle
int y_center;

int x;  // used for the algorithm to draw points on the border
int y;

int radius;

int r2 = radius * radius; // the radius sqaured

PutPixel( x_center, y_center + radius );
PutPixel( x_center, y_center - radius );
PutPixel( x_center + radius, y_center );
PutPixel( x_center - radius, y_center );

x = 1;
y = (int)( sqrt( r2 - 1 ) + 0.5 );

while( x < y ) {

  PutPixel( x_center + x, y_center + y );
  PutPixel( x_center + x, y_center - y );
  PutPixel( x_center - x, y_center + y );
  PutPixel( x_center - x, y_center - y );
  PutPixel( x_center + y, y_center + x );
  PutPixel( x_center + y, y_center - x );
  PutPixel( x_center - y, y_center + x );
  PutPixel( x_center - y, y_center - x );

  ++x;
  y = (int)( sqrt( r2 - x * x ) + 0.5 );
}
if (x == y) {

  PutPixel( x_center + x, y_center + y );
  PutPixel( x_center + x, y_center - y );
  PutPixel( x_center - x, y_center + y );
  PutPixel( x_center - x, y_center - y );
}

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does this help?

Code:

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void retro_circle(int xc, int yc, int r)
{
  int x,
      y,
      d,

  y = r;
  d = 1 - r;

  for (x = 0; x < y; x++)
  {
      if (d < 0)
      {
        d += x * 2 + 3;
      }
      else
      {
        d += x * 2 - y * 2 + 5;
        y--;
      }

      vga_drawpixel(xc + x, yc + y);
      vga_drawpixel(xc - x, yc + y);
      vga_drawpixel(xc + x, yc - y);
      vga_drawpixel(xc - x, yc - y);
      vga_drawpixel(xc + y, yc + x);
      vga_drawpixel(xc - y, yc + x);
      vga_drawpixel(xc + y, yc - x);
      vga_drawpixel(xc - y, yc - x);
  }
}

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thanks for all the help :) i got it working now