Re: Drawing a circle

["Ales Mlakar" <jazzbre@slo.net>]

Why don't you guys check Graphics Gems (there's a whole archive on the net
somewhere, do a search) for stuff like that, It has some on this subject
too.

----- Original Message -----
From: Kamel Serend <kserend@twowaytv.co.uk>
To: <gameprogrammer@gameprogrammer.com>
Sent: Friday, July 07, 2000 2:36 PM
Subject: RE: Drawing a circle


> Hi,
>
> Just a little question...
> Why nobody is using the Bresenham algorithm as applied to circles ?
> I thought it is the simpliest and fastest way to do the things, but I must
> be wrong...
> Any body ?
>
> Kamel
>
> > -----Original Message-----
> > From: Paul Robson [SMTP:probson@powerup.com.au]
> > Sent: Friday, July 07, 2000 12:44 PM
> > To: gameprogrammer@gameprogrammer.com
> > Subject: RE: Drawing a circle
> >
> > you could always do it using the circle formula.  It's a lot more
reliable
> > anyway, you don't get extra pixels being drawn on top of each other for
> > small circles or have large gaps for big circles (ie circles with a
radius
> > >
> > 360)
> >
> > the circle formula is r^2 = x^2 + y^2
> > this can be rearranged to be:  y = (plus-or-minus)sqrt(r^2-x^2)
> >
> > So, to implement this.. you would have something like this:
> >
> > void drawline(x1, y1, x2, y2);
> >
> > void drawcircle (x, y, r)
> > {
> >   int r2 = r*r;
> >   for (int i = x-r; i < x+r-1; i+=2)
> >   {
> >     j = i+1;
> >     drawline( i, sqrt( r2 - (i-x)*(i-x), j, sqrt( r2 - (j-x)*(j-x) );
> >     drawline( i, -sqrt( r2 - (i-x)*(i-x), j, -sqrt( r2 - (j-x)*(j-x) );
> >   }
> > }
> >
> > I think that should work.. i haven't actually typed it in or anything so
> > there's bound to be typos :)
> >
> > Paul Robson
> >
> > > -----Original Message-----
> > > From: gameprogrammer-owner@gameprogrammer.com
> > > [mailto:gameprogrammer-owner@gameprogrammer.com]On Behalf Of Kevin
Shea
> > > Sent: Friday, 7 July 2000 7:08 PM
> > > To: gameprogrammer@gameprogrammer.com
> > > Subject: Re: Drawing a circle
> > >
> > >
> > > On this whole subject of drawing circles, you simply don't want
> > > anything to do with sin()/cos() if you can avoid it.
> > >
> > > Since the original question was for c++/assembler, check out Michael
> > > Abrash's "Black Book of Graphics Programming" (something like that) -
> > > it has circle-drawing routines in C and assembly for (I think) various
> > > VGA modes.
> > >
> > > Kev
> > >
> > > Kevin Wolfskill wrote:
> > > >
> > >
> > > Lots cut out.
> > >
> > > > >----- Original Message -----
> > > > >From: Lionel Pinkhard <lionelpi@mweb.co.za>
> > > > >To: <gameprogrammer@gameprogrammer.com>
> > > > >Sent: Saturday, July 05, 1980 3:04 AM
> > > > >Subject: Drawing a circle
> > > > >
> > > > >
> > > > > > Hi,
> > > > > >
> > > > > > Can somebody please tell me how to draw a circle in
C++/Assembler
> > > > >without
> > > > >using any graphics libraries (so far my game's not using any)?
> > > (under DOS).
> > > > > >
> > > > > > Kind regards,
> > > > > >
> > > > > > Lionel Pinkhard
> > > > > >
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