Fixed since its previous release for increased accuracy. Use it wherever need be.

//       Overkill's atan2()


// Finds the angle from (x1,y1) to (x2,y2).


//


// Does all the bitshifting and such for you.


// Accuracy of angles has improved greatly!


//


//              9 0


//               |


//        0   --   --   1 8 0


//               |


//             2 7 0





int abs(int a)


{


 if (a<0) return 0-a;


 else return a;


}





int atan2(int x1, int y1, int x2, int y2)


{


 int x, y;


 int r, a;


 x=x2-x1;


 y=y2-y1;


 if (x)


 {


  r=y*65536/x;


 }


 else


 {


  r=y*65536*1000000; // Same as dividing by 0.0000001, instead of 0 which gives an infinite number.


 }


 a = atan(abs(r)); 


 if(x<0 && y>0)


 {


  a=180-a;


 }


 if(x<0 && y<0)


 {


  a=180+a;


 }


 if(x>0 && y<0)


 {


  a=0-a;


 }


 //This part doesn't mean anything, really...


 if(x>0 && y>0)


 {


  a=0+a;


 }





 if (a<0) a=360+a;


 if(x>0-2 && x<2)


 {


  if(y>0) a=90;


  else if(y<=0) a=270;


 }


 if(y>0-2 && y<2)


 {


  if(x>0) a=0;


  else if(x<=0) a=180;


 }


 return a;


}

The frame of reference is the absolute orientation of the screen. It's implied.

It should only need two points, as it figures out the x difference and ydifference which is used to find the angle to get from point A to point B. It works fine as far as I know.

Here's a test for it:

int screenx=ImageWidth(screen);


int screeny=ImageHeight(screen);


void Autoexec()


{


 int done;


 while(!done)


 {


  RectFill(0,0,screenx,screeny,rgb(0,0,0),screen);


  Printstring(0,0,screen,0,str(atan2(mouse.x,mouse.y,screenx/2,screeny/2) ) );


  Rect(mouse.x,mouse.y,mouse.x+8,mouse.y+8,rgb(255,255,255),screen);


  Line(mouse.x,mouse.y,screenx/2,screeny/2,rgb(20,102,255),screen);


  Line(mouse.x+8,mouse.y,screenx/2,screeny/2,rgb(20,102,255),screen);


  Line(mouse.x,mouse.y+8,screenx/2,screeny/2,rgb(20,102,255),screen);


  Line(mouse.x+8,mouse.y+8,screenx/2,screeny/2,rgb(20,102,255),screen);


  Showpage();


 }


 exit("");


}

---

Edit: Crap! The example shows that it goes from x2, y2 to x1, y1. I think I screwed up there, but that's easily fixable with a little tweaking.

Also: I note that this function doesn't do that much, really. If I did anything more, it'd be in a demo of some sort.