Re: ASCII meets games

On Sun, 2 Apr 2000 19:07:38 +0200, "Nacken" <jna...@casema.net>
wrote:
[...]
>I do a lot of programming in QuickBasic. Right now, I'm working on
>a game, especially for the old XT-pc's. Therefore, I can't draw lines or set
>points, and I must use the ASCII-characters for a substitute for gfx. 

A) There is aa-lib library for C-language on Linux system. Maybe You
should watch its sources, and see how the graphics is made.

B) How old is your XT-pc? Haven't it either HGC graphic card? 8-O

C) The simplest agoritm is drawing horizontal/vertical line. You 
should use '|' and ('-' or '_') signs. 

Let's assume that parameters of procedure are (x1,y1, x2,y2) - x-y 
positions of beginning and end of line. Its also possible to use tilda

('~') sign, but it's height is different in different fonts.

For horizontal line use:
for i=x1 to x2
  print at (i,y1) "-"        {sorry, I don't remember QB syntax :-(} 
next i

For vertical line use:
for i=y1 to y2
  print at (x1,i) "|"
next i

It is also simple to draw 45/135 degree lines. Guess how? ;-)

The more difficult is drawing lines with other angles.
Algoritm could be like that:
0) check that y1<>y2. In other case you'll get "Division by zero"
error in next point!
1) alfa = arctan((y2-y1)/(x2-x1)) 
2) if alfa > 45[1] degrees you should use "for y" loop
if not, "for x" loop would be better.
2a) if alfa < 45 then line should look like this:

          1 2 3 4 5 6 7 8 9 segments
          | | | | | | | | |  

1 y1-     --..__
2               ``--..__
3 y2-                   ``---
         |                  |
         x1                 x2
         12345678901234567890

so for each character line (|y2-y1| gives you number of lines) you
should use four characters. Count number of different segments...

  numparts=(|y2-y1| * 4)+1            {|3-1|*4 +1 = 9}

...and number of character for one segment:

  numchar=(|x2-x1| div numparts)      {(|20-1| div 9) = 2}

Now, two nested loops (inside should be loop for drawing one segment, 
and outside loop would be "for x" loop) should work fine.

2b) Algoritm is analogue to 2a), but I don't know which characters
you should use. :-( See a.a-a FAQ.

And that's all. Hope it will help you. :-)

[1] I know, this is not full condition, but...

PS.Sorry for my language, I'm not English native-speaker :-)
-- 
    Rafal Slubowski                \\
raf...@paputek.decsoft.com.pl      /O `----. 
    www.slubek.w.pl            * (_.-.     )\
                              *|* rs //--//  X

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