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/*
* dir.cc - Directions.
*
* Copyright (C) 1998-1999 Jeffrey S. Freedman
* Copyright (C) 2000-2022 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"
#include "exult_constants.h"
static int Wrap_Delta(int delta) {
if (delta >= c_num_tiles / 2) { // World-wrapping.
return c_num_tiles / 2 - delta;
} else if (delta <= -c_num_tiles / 2) {
return -c_num_tiles / 2 - delta;
} else {
return delta;
}
}
/*
* Return the direction for a given slope (0-7).
* NOTE: Assumes cartesian coords, NOT screen coords. (which have y
* growing downwards).
*/
Direction Get_direction_NoWrap(int deltay, int deltax) {
if (deltax == 0) {
return deltay > 0 ? north : south;
}
const 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).
* NOTE: Assumes cartesian coords, NOT screen coords. (which have y
* growing downwards).
*/
Direction Get_direction(int deltay, int deltax) {
return Get_direction_NoWrap(Wrap_Delta(deltay), Wrap_Delta(deltax));
}
/*
* 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) {
deltax = Wrap_Delta(deltax);
deltay = Wrap_Delta(deltay);
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) {
deltax = Wrap_Delta(deltax);
deltay = Wrap_Delta(deltay);
if (deltax == 0) {
return deltay > 0 ? 0 : 8;
}
const int dydx = (1024 * deltay) / deltax; // Figure 1024*tan.
const 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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