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/*
* dir.cc - Directions.
*
* Copyright (C) 1998-1999 Jeffrey S. Freedman
* Copyright (C) 2000-2001 The Exult Team
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include "dir.h"
/*
* Return the direction for a given slope (0-7).
* NOTE: Assumes cartesian coords, NOT screen coords. (which have y
* growing downwards).
*/
Direction Get_direction
(
int deltay,
int deltax
)
{
if (deltax == 0)
return deltay > 0 ? north : south;
int dydx = (1024*deltay)/deltax;// Figure 1024*tan.
if (dydx >= 0)
if (deltax >= 0) // Top-right quadrant?
return dydx <= 424 ? east : dydx <= 2472 ? northeast
: north;
else // Lower-left.
return dydx <= 424 ? west : dydx <= 2472 ? southwest
: south;
else
if (deltax >= 0) // Lower-right.
return dydx >= -424 ? east : dydx >= -2472 ? southeast
: south;
else // Top-left?
return dydx >= -424 ? west : dydx >= -2472 ? northwest
: north;
}
/*
* Return the direction for a given slope (0-7), rounded to NSEW.
* NOTE: Assumes cartesian coords, NOT screen coords. (which have y
* growing downwards).
*/
Direction Get_direction4
(
int deltay,
int deltax
)
{
if (deltax >= 0) // Right side?
return (deltay > deltax ? north : deltay < -deltax ? south
: east);
else // Left side.
return (deltay > -deltax ? north : deltay < deltax ? south
: west);
}
/*
* Return the direction for a given slope (0-15).
* NOTE: Assumes cartesian coords, NOT screen coords. (which have y
* growing downwards).
*/
int Get_direction16
(
int deltay,
int deltax
)
{
if (deltax == 0)
return deltay > 0 ? 0 : 8;
int dydx = (1024*deltay)/deltax;// Figure 1024*tan.
int adydx = dydx < 0 ? -dydx : dydx;
int angle = 0;
if (adydx < 1533) // 1024*tan(5*11.25)
{
if (adydx < 204) // 1024*tan(11.25).
angle = 4;
else if (adydx < 684) // 1024*tan(3*11.25).
angle = 3;
else
angle = 2;
}
else
{
if (adydx < 5148) // 1024*tan(7*11.25).
angle = 1;
else
angle = 0;
}
if (deltay < 0) // Check quadrants.
if (deltax > 0)
angle = 8 - angle;
else
angle += 8;
else if (deltax < 0)
angle = 16 - angle;
return angle % 16;
}
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