karma/flying-balls
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added collisions.

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This commit is contained in:
Antonio Carzaniga 2019-06-03 22:24:06 +02:00
parent ce4e4cbc2d
commit f46f20aa81
2 changed files with 64 additions and 27 deletions
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3
Makefile
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@ -5,8 +5,7 @@ GTK_LIBS=$(shell pkg-config --libs $(GTK_PACKAGES))
# CFLAGS=-Wall -g -O2 -std=c11 -pthread $(GTK_CFLAGS) # CFLAGS=-Wall -g -O2 -std=c11 -pthread $(GTK_CFLAGS)
CFLAGS=-Wall -g -O2 $(GTK_CFLAGS) CFLAGS=-Wall -g -O2 $(GTK_CFLAGS)
# LIBS=$(GTK_LIBS) -lm LIBS=$(GTK_LIBS) -lm
LIBS=$(GTK_LIBS)
PROGS=balls PROGS=balls

72
balls.c
View File

@ -12,15 +12,15 @@
#define DEFAULT_HEIGHT 800 #define DEFAULT_HEIGHT 800
struct ball { struct ball {
float x; double x;
float y; double y;
unsigned int radius; unsigned int radius;
float v_x; double v_x;
float v_y; double v_y;
}; };
static float delta = 0.01; static double delta = 0.01;
static unsigned int width = 0; static unsigned int width = 0;
static unsigned int height = 0; static unsigned int height = 0;
@ -30,10 +30,10 @@ static unsigned int ball_radius = 4;
struct ball * balls = 0; struct ball * balls = 0;
unsigned int n_balls = 10; unsigned int n_balls = 10;
static float g_y = 20; static double g_y = 20;
static float g_x = 0; static double g_x = 0;
void balls_init_state() { void balls_init_state () {
srand(time(NULL)); srand(time(NULL));
static const unsigned int border = 10; static const unsigned int border = 10;
unsigned int w = width < 2*border ? 1 : width - 2*border; unsigned int w = width < 2*border ? 1 : width - 2*border;
@ -43,7 +43,32 @@ void balls_init_state() {
balls[i].y = border + rand() % h; balls[i].y = border + rand() % h;
balls[i].v_x = rand() % 100; balls[i].v_x = rand() % 100;
balls[i].v_y = rand() % 100; balls[i].v_y = rand() % 100;
balls[i].radius = ball_radius + rand() % 10; balls[i].radius = ball_radius + rand() % 20;
}
}
static void ball_collision (struct ball * p, struct ball * q) {
double dx = q->x - p->x;
double dy = q->y - p->y;
double d2 = dx*dx + dy*dy;
double r = p->radius + q->radius;
if (d2 <= r*r) {
double dv_x = q->v_x - p->v_x;
double dv_y = q->v_y - p->v_y;
double mp = p->radius * p->radius;
double mq = q->radius * q->radius;
double f = dv_x*dx + dv_y*dy;
if (f < 0) {
f /= d2*(mp + mq);
p->v_x += 2*mq*f*dx;
p->v_y += 2*mq*f*dy;
q->v_x -= 2*mp*f*dx;
q->v_y -= 2*mp*f*dy;
}
} }
} }
@ -55,26 +80,34 @@ static void ball_update_state (struct ball * p) {
p->v_y += delta*g_y; p->v_y += delta*g_y;
if (p->x + p->radius > width) { if (p->x + p->radius > width) {
if (p->v_x > 0) {
p->x -= p->x + p->radius - width; p->x -= p->x + p->radius - width;
p->v_x = -p->v_x; p->v_x = -p->v_x;
}
} else if (p->x < p->radius) { } else if (p->x < p->radius) {
if (p->v_x < 0) {
p->x += p->radius - p->x; p->x += p->radius - p->x;
p->v_x = -p->v_x; p->v_x = -p->v_x;
} }
}
if (p->y + p->radius > height) { if (p->y + p->radius > height) {
if (p->v_y > 0) {
p->y -= p->y + p->radius - height; p->y -= p->y + p->radius - height;
p->v_y = -p->v_y; p->v_y = -p->v_y;
}
} else if (p->y < p->radius) { } else if (p->y < p->radius) {
if (p->v_y < 0) {
p->y += p->radius - p->y; p->y += p->radius - p->y;
p->v_y = -p->v_y; p->v_y = -p->v_y;
} }
}
} }
static GdkPixbuf * pixbuf = 0; static GdkPixbuf * pixbuf = 0;
static float clear_alpha = 1.0; static double clear_alpha = 1.0;
static void destroy_surface() { static void destroy_surface () {
if (pixbuf) if (pixbuf)
g_object_unref(pixbuf); g_object_unref(pixbuf);
@ -104,6 +137,10 @@ static void create_surface(int w, int h) {
} }
static void update_state() { static void update_state() {
for(int i = 0; i < n_balls; ++i)
for(int j = i + 1; j < n_balls; ++j)
ball_collision(balls + i, balls + j);
for(int i = 0; i < n_balls; ++i) for(int i = 0; i < n_balls; ++i)
ball_update_state(balls + i); ball_update_state(balls + i);
} }
@ -120,8 +157,9 @@ static void do_draw(GtkWidget * widget) {
for(int y = 0; y < height; ++y) { for(int y = 0; y < height; ++y) {
unsigned char * px = pixels + y*row_stride; unsigned char * px = pixels + y*row_stride;
for(int x = 0; x < width; ++x) { for(int x = 0; x < width; ++x) {
for(int i = 0; i < n_channels; ++i) *px++ *= 0.95;
*px++ = 0; *px++ *= 0.90;
*px++ *= 0.80;
} }
} }
} else { } else {
@ -229,15 +267,15 @@ int main(int argc, const char *argv[]) {
continue; continue;
if (sscanf(argv[i], "n=%u", &n_balls) == 1) if (sscanf(argv[i], "n=%u", &n_balls) == 1)
continue; continue;
if (sscanf(argv[i], "trace=%f", &clear_alpha) == 1) if (sscanf(argv[i], "trace=%lf", &clear_alpha) == 1)
continue; continue;
if (sscanf(argv[i], "fx=%f", &g_x) == 1) if (sscanf(argv[i], "fx=%lf", &g_x) == 1)
continue; continue;
if (sscanf(argv[i], "fy=%f", &g_y) == 1) if (sscanf(argv[i], "fy=%lf", &g_y) == 1)
continue; continue;
if (sscanf(argv[i], "radius=%u", &ball_radius) == 1) if (sscanf(argv[i], "radius=%u", &ball_radius) == 1)
continue; continue;
if (sscanf(argv[i], "delta=%f", &delta) == 1) if (sscanf(argv[i], "delta=%lf", &delta) == 1)
continue; continue;
print_usage(argv[0]); print_usage(argv[0]);
return 1; return 1;