Re: [Dev-C++] Drawing Lines...

[Jason H. <jas...@bt...>]

I have a nasty habit of overkill. Sorry. Besides there's a gaping big flaw
in the algo I supplied, but it was only just to demonstrate a point (sorry,
bad pun :).

Jason.

----- Original Message -----
From: "St0fF 64" <st...@gm...>
To: <dev...@li...>
Sent: Tuesday, November 06, 2001 2:44 PM
Subject: Re: [Dev-C++] Drawing Lines...


> Thanks to Jason for explaining Bresenham's algorithm.  I'm sure Dx Fx
needs
> to get to know about some pretty nice helpers: Books and search engines.
> Hunting with a goot search engine on '+drawing +lines' would probably have
> been enough ...
>
> St0fF.
>
> ----- Original Message -----
> From: "Jason Hardman" <jas...@bt...>
> To: "Dev-C++" <dev...@li...>; "<Dx 8a>"
> <vin...@ed...>
> Sent: Sunday, November 04, 2001 3:26 AM
> Subject: Re: [Dev-C++] Drawing Lines...
>
>
> > Hello! Me again. Probably sick of me replying all the time and not being
> > helpful enough.
> >
> > I'm not sure of your level of maths knowledge, but I'll put it simply
and
> > elaborate later (if you want). There are algorithms for drawing lines
that
> > are optimised for speed and can do things like anti-aliasing, but to do
a
> > simple line with simple maths then all you need to know is how to
> calculate
> > the gradient of the line.
> >
> > If I had a pen and paper and could explain it that way it would be
easier,
> > but I'll try in writing.
> >
> > By calculating the gradient you can then tell how much y increases (or
> > decreases) for each one of x (or x of y) i.e.
> > Assuming x1 (start) is smaller than x2 (end), i.e. line going left to
> right
> > on a screen. If not the case just swap coords around.
> >
> > double gradient, dx, dy, x, y;
> >
> > dx = x1 - x2; // change in x
> > dy = y1 - y2; // change in y
> >
> > gradient = dy/dx;
> >
> > for(x = x1, y = y1; x <= x2; ++x, y += gradient)
> >     putpixel(static_cast<int>(x), static_cast<int>(y), colour);
> > /* proper rounding would be better, but simple rounding down of decimals
> in
> > double to int conversion should be OK */
> >
> > This is a guide of what you might do. I've not tested it, but AFAICT the
> > math is OK. With a little more work you should be able to go in any
> > direction. Other algorithms avoid the use of floating point
representation
> > cos it's slower than integer maths.
> >
> > I'll go into putpixel later if you want, but first can I ask what are
you
> > trying to do (apart from draw a line)? If you are working in a window
then
> > there are a broad set of drawing functions available for use, i.e.
> LineTo(),
> > Polygon(), Rectangle() etc... and they can be used on a DirectX app if
> need
> > be? I hope I'm not confusing the issue?
> >
> > Jason.
> >
> > ----- Original Message -----
> > From: "<Dx 8a>" <vin...@ed...>
> > To: "Dev-C++ mailing list" <dev...@li...>
> > Sent: Sunday, November 04, 2001 1:31 AM
> > Subject: [Dev-C++] Drawing Lines...
> >
> >
> > > Ok guys, I'll put it all together, and hopefully I can get the
point...
> > >
> > > Using a library might be a good choice... I'tll save me a lot of time
> and
> > effort... But I surely don't know where I can get from so I guess I'll
> have
> > to do things manually.
> > >
> > > And yes, I think, DirectX doesn't supply a PutPixel or something to
put
> > points on the screen... That's why Ill have to make my own functions...
> > >
> > > Also, there must be someway of doing this thing mathematically... I
> found
> > that on a tutorial... that drawing pixels in the screen can be done
> > mathematically... although, the tutorial didn't included a formula in
> > drawing a straight line on the screen... Does anyone know of such a
> formula?
> > >
> > > Drawing the pixel on the screen would require me to access the memory
> > buffer or something... Ill have to make a function to simplify the task
> and
> > do a PutPixel...
> > >
> > > am I missing something? I hope I got it right, ive actually started
> coding
> > a few days earlier... and caused my system to crash... the reason I
don't
> > really know... but it sure wasn't the programming I did... which also
> > prevented me to check the mailing list...
> > >
> > > Well guys, thanks in many ways... although I'll leave the still
> unanswered
> > question...
> > >
> > >
> > >
> > >
> > > How do I draw Straight lines on the screen? (using DirectX)
> > >
> > >
> > > Specifically, now Im asking of a formula that would make it sure that
> what
> > I'm drawing is a straight line... the previous things in the mailing
list
> > have actually helped me to know what Ill actually have to do In doing
the
> > drawing... Well... i hope someone could enlighten me somehow
> > >
> > > Thanks...
> > >
> > > Dx Fx
> > >
> > > __________________________________
> > > www.edsamail.com
> > >
> > > _______________________________________________
> > > Dev-cpp-users mailing list
> > > Dev...@li...
> > > https://lists.sourceforge.net/lists/listinfo/dev-cpp-users
> >
> >
> > _______________________________________________
> > Dev-cpp-users mailing list
> > Dev...@li...
> > https://lists.sourceforge.net/lists/listinfo/dev-cpp-users
>
>
>
>
> _______________________________________________
> Dev-cpp-users mailing list
> Dev...@li...
> https://lists.sourceforge.net/lists/listinfo/dev-cpp-users