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/*
* Copyright (C) 2021 P. J. McDermott
*
* This file is part of Dodge Balls
*
* Dodge Balls 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 3 of the License, or
* (at your option) any later version.
*
* Dodge Balls 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 Dodge Balls. If not, see <http://www.gnu.org/licenses/>.
*/
#include <SDL.h>
#include "collision.h"
int
db_pt_in_rect(int x, int y, SDL_Rect *rect)
{
if (x < rect->x) {
return 0;
}
if (y < rect->y) {
return 0;
}
if (x > rect->x + rect->w) {
return 0;
}
if (y > rect->y + rect->h) {
return 0;
}
return 1;
}
int
db_col_cir_line(double cir_x, double cir_y, double cir_r,
int line_x1, int line_y1, int line_x2, int line_y2,
double *col_x, double *col_y)
{
int line_min;
int line_max;
if (line_y1 == line_y2) {
/* Horizontal line */
if (line_x1 < line_x2) {
line_min = line_x1;
line_max = line_x2;
} else {
line_min = line_x2;
line_max = line_x1;
}
if (cir_x < line_min) {
*col_x = line_min;
} else if (cir_x > line_max) {
*col_x = line_max;
} else {
*col_x = cir_x;
}
*col_y = line_y1;
} else if (line_x1 == line_x2) {
/* Vertical line */
if (line_y1 < line_y2) {
line_min = line_y1;
line_max = line_y2;
} else {
line_min = line_y2;
line_max = line_y1;
}
if (cir_y < line_min) {
*col_y = line_min;
} else if (cir_y > line_max) {
*col_y = line_max;
} else {
*col_y = cir_y;
}
*col_x = line_x1;
} else {
return -1;
}
return (cir_r * cir_r) >
((*col_x - cir_x) * (*col_x - cir_x) +
(*col_y - cir_y) * (*col_y - cir_y));
}
void
db_closest_pt_on_rect(int x, int y, SDL_Rect *rect,
double *close_x, double *close_y)
{
*close_x = x;
if (x < rect->x) {
*close_x = rect->x;
} else if (x > rect->x + rect->w) {
*close_x = rect->x + rect->w;
}
*close_y = y;
if (y < rect->y) {
*close_y = rect->y;
} else if (y > rect->y + rect->h) {
*close_y = rect->y + rect->h;
}
}
int
db_col_cir_rect(int x, int y, int r, SDL_Rect *rect,
double *col_x, double *col_y)
{
db_closest_pt_on_rect(x, y, rect, col_x, col_y);
return (r * r) >=
((*col_x - x) * (*col_x - x) + (*col_y - y) * (*col_y - y));
}
int
db_col_cir_cir(double x1, double y1, double r1, double x2, double y2, double r2)
{
return ((r1 + r2) * (r1 + r2)) >=
((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
}
/*
* This function will be called after moving the two balls being checked. A
* more accurate way to handle collisions would be to microstep through
* movements to find the exact point of collision.
*/
int
db_col_pt_cir_cir(double x1, double y1, double r1,
double x2, double y2, double r2, double *col_x, double *col_y)
{
if (db_col_cir_cir(x1, y1, r1, x2, y2, r2)) {
*col_x = (x1 + x2) / 2.0;
*col_y = (y1 + y2) / 2.0;
return 1;
} else {
return 0;
}
}
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