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From: "Zenko B. Klapko Jr." <zen1 AT comcast DOT net>
Subject: allegro and math libraries
Newsgroups: comp.os.msdos.djgpp
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Date: Thu, 10 Jan 2002 23:10:57 GMT
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To: djgpp AT delorie DOT com
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Reply-To: djgpp AT delorie DOT com

Hello Everybody!

For a week or two I've been trying to get a line to rotate like a
propeller. I'm using the allegro and math libraries and I"m wondering
what i'm doing wrong. I felt this would be a proper place for it since
the programmers here are well educated and show concern for the people
who post. And I've asked 3 math teachers (2 of which program) for help but to no
avail. I've even tinkered with the equaitons and created really amazing
cylinders and other circular based patterns, but I really would like a
rotating line. Heres the Code and thanks for any time spent! -Zen
PS. if you have a simpler example that will do.

#include <dos.h>
#include <conio.h>
#include <iostream.h>
#include <math.h>
#include <allegro.h> //contains code for allegro library

void info();
void numtest();

int main()
{
 allegro_init(); //sets up allegro environment

 set_gfx_mode(GFX_VESA1,640,480,0,0);   //sets gfx info

  numtest();
return 0;
};
void numtest() //MUST CREATE 4 QUADRANTS ON SCREEN?
{   double xpos=100,ypos=100,xpos2=200,ypos2=200,rad,xang,yang,xang2,yang2;
  clear(screen);
//  line(screen,int(xpos),int(ypos),int(xpos2),int(ypos2),10);
  for (int ang=1;ang <=360;ang++)
  {
   rad=ang*(3.1415/180);
   xang=50*cos(rad)-50*sin(rad);
   yang=50*sin(rad)+50*cos(rad);
   xang2=50*sin(rad)-50*cos(rad);
   yang2=50*cos(rad)+50*sin(rad);
/*   if (ang <= 90)
   {*/
   xpos-=xang;
   ypos-=yang;

   xpos2+=xang;
   ypos2+=yang;
 /* }
   if ((ang > 90) && (ang <= 180))
   {
   xpos+=xang;
   ypos+=xang;
   xpos2-=xang;
   ypos2-=yang;
   }*/
   /*
   if ((ang > 180) && (ang <= 270))
   {
   
   xpos+=xang;
   ypos+=xang;
   xpos2-=xang;
   ypos2-=yang;
   }
   if ((ang > 270) && (ang <= 360))
   {
   xpos-=xang;
   ypos+=yang;
   xpos2+=xang;
   ypos2-=yang;
   } */
   
   line(screen,int(xpos),int(ypos),int(xpos2),int(ypos2),10);
   xpos=100; ypos=100; xpos2=200; ypos2=200;
   if (getch() == 'q')
               ang=359;

 }
 getch();

return;
};