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b2c96f75c1
flying-balls/balls.c
Antonio Carzaniga b2c96f75c1 keyboard-controlled gravity vector
2019-07-28 15:03:27 +02:00

320 lines
7.5 KiB
C
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#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <math.h>
#include <time.h>
#include <gdk/gdkkeysyms.h>
#include <gdk-pixbuf/gdk-pixbuf.h>
#include <gtk/gtk.h>
#define DEFAULT_WIDTH 800
#define DEFAULT_HEIGHT 800
struct ball {
double x;
double y;
unsigned int radius;
double v_x;
double v_y;
guchar rgb_channels[3];
};
static double delta = 0.01; /* seconds */
static unsigned int width = DEFAULT_WIDTH;
static unsigned int height = DEFAULT_HEIGHT;
static unsigned int radius_min = 5;
static unsigned int radius_max = 10;
static unsigned int v_max = 100;
static unsigned int v_min = 0;
struct ball * balls = 0;
unsigned int n_balls = 50;
static double g_y = 20;
static double g_x = 0;
void random_velocity(struct ball * p) {
double r2;
do {
p->v_x = v_min + rand() % (v_max + 1 - v_min);
p->v_y = v_min + rand() % (v_max + 1 - v_min);
r2 = p->v_x*p->v_x + p->v_y*p->v_y;
} while (r2 > v_max*v_max || r2 < v_min*v_min);
}
void balls_init_state () {
srand(time(NULL));
static const unsigned int border = 10;
unsigned int w = width < 2*border ? 1 : width - 2*border;
unsigned int h = height < 2*border ? 1 : height - 2*border;
for (unsigned int i = 0; i < n_balls; ++i) {
balls[i].x = border + rand() % w;
balls[i].y = border + rand() % h;
random_velocity(balls + i);
if (rand() % 2)
balls[i].v_x = -balls[i].v_x;
if (rand() % 2)
balls[i].v_y = -balls[i].v_y;
balls[i].radius = radius_min + rand() % (radius_max + 1 - radius_min);
balls[i].rgb_channels[0] = rand() % 256;
balls[i].rgb_channels[1] = rand() % 256;
balls[i].rgb_channels[2] = rand() % 256;
}
}
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;
}
}
}
static void ball_update_state (struct ball * p) {
p->x += delta*p->v_x + delta*delta*g_x/2.0;
p->v_x += delta*g_x;
p->y += delta*p->v_y + delta*delta*g_y/2.0;
p->v_y += delta*g_y;
if (p->x + p->radius > width) {
if (p->v_x > 0) {
p->x -= p->x + p->radius - width;
p->v_x = -p->v_x;
}
} else if (p->x < p->radius) {
if (p->v_x < 0) {
p->x += p->radius - p->x;
p->v_x = -p->v_x;
}
}
if (p->y + p->radius > height) {
if (p->v_y > 0) {
p->y -= p->y + p->radius - height;
p->v_y = -p->v_y;
}
} else if (p->y < p->radius) {
if (p->v_y < 0) {
p->y += p->radius - p->y;
p->v_y = -p->v_y;
}
}
}
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)
ball_update_state(balls + i);
}
static GtkWidget * window;
static cairo_t * cr = 0;
static void draw_gravity_vector() {
cairo_new_path(cr);
cairo_move_to(cr, width/2, height/2);
cairo_line_to(cr, width/2 + g_x, height/2 + g_y);
cairo_set_source_rgb(cr, 1.0, 1.0, 1.0);
cairo_set_line_width(cr, 1.0);
cairo_stroke(cr);
cairo_arc(cr, width/2 + g_x, height/2 + g_y, 3, 0, 2*M_PI);
cairo_fill(cr);
}
static void draw_balls_onto_window () {
if (!cr)
cr = gdk_cairo_create(window->window);
/* clear pixmap */
cairo_set_source_rgba(cr, 0.0, 0.0, 0.0, 1.0);
cairo_paint(cr);
draw_gravity_vector();
/* draw balls */
for(int i = 0; i < n_balls; ++i) {
cairo_set_source_rgb(cr,
1.0*balls[i].rgb_channels[0]/255,
1.0*balls[i].rgb_channels[1]/255,
1.0*balls[i].rgb_channels[2]/255);
cairo_arc(cr, balls[i].x, balls[i].y, balls[i].radius, 0, 2 * M_PI);
cairo_fill(cr);
}
}
static gint resize_event (GtkWidget *widget, GdkEventConfigure * event) {
if (width == widget->allocation.width && height == widget->allocation.height)
return FALSE;
width = widget->allocation.width;
height = widget->allocation.height;
if (cr) {
cairo_destroy(cr);
cr = gdk_cairo_create(window->window);
}
draw_balls_onto_window();
return TRUE;
}
static gint keyboard_input (GtkWidget *widget, GdkEventKey *event) {
if (event->type != GDK_KEY_PRESS)
return FALSE;
switch(event->keyval) {
case GDK_KEY_Up:
g_y -= 10;
break;
case GDK_KEY_Down:
g_y += 10;
break;
case GDK_KEY_Left:
g_x -= 10;
break;
case GDK_KEY_Right:
g_x += 10;
break;
case GDK_KEY_F:
case GDK_KEY_f:
g_x = rand() % 201 - 100;
g_y = rand() % 201 - 100;
break;
case GDK_KEY_Q:
case GDK_KEY_q:
gtk_main_quit();
break;
default:
return FALSE;
}
return TRUE;
}
static gboolean expose_event (GtkWidget *widget, GdkEventExpose *event, gpointer data) {
return TRUE;
}
static void destroy_window (void) {
gtk_main_quit();
if (cr) {
cairo_destroy(cr);
cr = 0;
}
}
void print_usage (const char * progname) {
fprintf(stderr,
"usage: %s [options...]\n"
"options:\n"
"\t<width>x<height>\n"
"\tn=<bumber of balls>\n"
"\tfx=<x-force>\n"
"\tfy=<y-force>\n"
"\tradius=<min-radius>-<max-radius>\n"
"\tv=<min-velocity>-<max-velocity>\n"
"\tdelta=<frame-delta-time>\n",
progname);
}
gboolean timeout (gpointer user_data) {
guint64 start = g_get_monotonic_time ();
update_state();
draw_balls_onto_window();
guint64 elapsed_usec = g_get_monotonic_time () - start;
static guint64 elapsed_usec_total = 0;
static unsigned int samples = 0;
if (samples == 30) {
printf("\rtime for one frame: %lu usec (avg over %u samples) ", elapsed_usec_total / samples, samples);
fflush(stdout);
samples = 0;
elapsed_usec_total = 0;
}
++samples;
elapsed_usec_total += elapsed_usec;
return TRUE;
}
int main (int argc, const char *argv[]) {
int w = DEFAULT_WIDTH;
int h = DEFAULT_HEIGHT;
for (int i = 1; i < argc; ++i) {
if (sscanf(argv[i], "%dx%d", &w, &h) == 2)
continue;
if (sscanf(argv[i], "n=%u", &n_balls) == 1)
continue;
if (sscanf(argv[i], "fx=%lf", &g_x) == 1)
continue;
if (sscanf(argv[i], "fy=%lf", &g_y) == 1)
continue;
if (sscanf(argv[i], "radius=%u-%u", &radius_min, &radius_max) == 2)
continue;
if (sscanf(argv[i], "v=%u-%u", &v_min, &v_max) == 2)
continue;
if (sscanf(argv[i], "delta=%lf", &delta) == 1)
continue;
print_usage(argv[0]);
return 1;
}
balls = malloc(sizeof(struct ball)*n_balls);
assert(balls);
balls_init_state();
gtk_init(0, 0);
window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
assert(window);
gtk_window_set_default_size(GTK_WINDOW(window), w, h);
gtk_window_set_position(GTK_WINDOW(window), GTK_WIN_POS_CENTER);
gtk_window_set_title(GTK_WINDOW(window), "Balls");
g_signal_connect(window, "destroy", G_CALLBACK(destroy_window), NULL);
g_signal_connect(window, "expose-event", G_CALLBACK(expose_event), NULL);
g_signal_connect(window, "configure_event", G_CALLBACK(resize_event), NULL);
g_signal_connect(window, "key_press_event", G_CALLBACK(keyboard_input), NULL);
gtk_widget_set_events (window, GDK_EXPOSURE_MASK | GDK_BUTTON_PRESS_MASK | GDK_KEY_PRESS_MASK);
g_timeout_add (delta * 1000, timeout, window);
gtk_widget_show_all(window);
gtk_main();
free(balls);
return 0;
}
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