ADD: EPPUR SI MUOVE !

main.c

@@ -11,7 +11,7 @@
 
 #define SUN_RADIUS 50
 
-#define DELTA_T 3600.0
+#define DELTA_T 8000.0
 
 int main() {
 	srand(time(NULL));
@@ -32,7 +32,6 @@ int main() {
 		// end : draw state of system
 		// begin : update your system
 		update_system(&sys, DELTA_T);
-		usleep(100000);
 		// end : update system
 		if (gfx_keypressed() == SDLK_ESCAPE) { break; }
 	}

planet/constants.h

@@ -2,6 +2,10 @@
 #define PLANET_CONSTANTS_H
 
 
+// display
+#define DISPLAY_RADIUS_DIV 1.0e23
+
+
 #define G 6.67e-11
 #define M_SOLEIL 1.989e30
 

planet/planet.c

@@ -20,22 +20,22 @@ system_t create_system(double delta_t) {
 	system.star = create_planet(M_SOLEIL, vec2_create_zero());
 	system.nb_planets = 4;
 	system.planets = malloc(system.nb_planets * sizeof(planet_t));
-	double masses[NB_PLANETS] = {
+	double masses[] = {
 			M_MERCURE,
 			M_VENUS,
 			M_TERRE,
 			M_MARS};
-	vec2 positions[NB_PLANETS] = {
+	vec2 positions[] = {
 			vec2_create(PER_MERCURE, 0.0),
 			vec2_create(PER_VENUS, 0.0),
 			vec2_create(PER_TERRE, 0.0),
 			vec2_create(PER_MARS, 0.0)};
-	double eccentricities[NB_PLANETS] = {
+	double eccentricities[] = {
 			E_MERCURE,
 			E_VENUS,
 			E_TERRE,
 			E_MARS};
-	double axis_major[NB_PLANETS] = {
+	double axis_major[] = {
 			A_MERCURE,
 			A_VENUS,
 			A_TERRE,
@@ -55,9 +55,12 @@ system_t create_system(double delta_t) {
 }
 
 
-void show_system(struct gfx_context_t* ctxt, system_t* system, const uint32_t width, const uint32_t height) {
+void show_system(struct gfx_context_t* ctxt, system_t* system) {
 	// draw sun
-	const coordinates xy_sun = vec2_to_coordinates_centered(vec2_normalize(system->star.pos), width, height);
+	const coordinates xy_sun = vec2_to_coordinates_centered(
+			vec2_normalize(system->star.pos),
+			ctxt->width,
+			ctxt->height);
 	draw_full_circle(ctxt, xy_sun.column, xy_sun.row, 50, COLOR_YELLOW);
 	// draw planets
 	for (uint32_t i = 0; i < system->nb_planets; ++i) {
@@ -85,12 +88,14 @@ void update_system(system_t* system, double delta_t) {
 			const vec2 a_k = vec2_mul(a_norm, u);
 			a = vec2_add(a, a_k);
 		}
+		a = vec2_mul(-1.0, a);  // correct sign: towards center
 		// update position
 		vec2 next_pos = vec2_mul(2.0, system->planets[i].pos);
 		next_pos = vec2_sub(next_pos, system->planets[i].prec_pos);
 		next_pos = vec2_add(next_pos, vec2_mul(delta_t * delta_t, a));
 		system->planets[i].prec_pos = system->planets[i].pos;
 		system->planets[i].pos = next_pos;
+		printf("%lf  %lf  %lf\n", system->planets[i].pos.x, system->planets[i].pos.y, vec2_norm(a));
 	}
 }
 

planet/planet.h

@@ -22,8 +22,7 @@ planet_t create_planet(double mass, vec2 pos);
 
 system_t create_system(double delta_t);
 
-//void show_system(struct gfx_context_t *ctxt, system_t *system);
-void show_system(struct gfx_context_t* ctxt, system_t* system, const uint32_t width, const uint32_t height);
+void show_system(struct gfx_context_t* ctxt, system_t* system);
 
 void update_system(system_t* system, double delta_t);