Prevent asteroids from spawning overlapped

game.c

@@ -144,7 +144,7 @@ static void shoot()
 	memcpy(s->verts, shot_verts, sizeof(shot_verts));
 }
 
-static entity_t *gen_asteroid(float r_mean)
+static entity_t *gen_asteroid(float r_mean, unsigned *id_out)
 {
 	unsigned id;
 	entity_t *e = add_entity(&id);
@@ -168,9 +168,28 @@ static entity_t *gen_asteroid(float r_mean)
 		s->verts[i] = (vec2_t) { r * cosf(a), r * sinf(a) };
 	}
 
+	if (id_out)
+		*id_out = id;
 	return e;
 }
 
+static bool intersecting(unsigned a, unsigned b)
+{
+	const float sep = vec2_len(vec2_sub(entities[b].pos, entities[a].pos));
+	return sep <= entities[a].radius + entities[b].radius;
+}
+
+static bool intersecting_any(unsigned id)
+{
+	for (unsigned i = 0; i < entity_count; ++i) {
+		if (i == id)
+			continue;
+		if (intersecting(id, i))
+			return true;
+	}
+	return false;
+}
+
 static void spawn_asteroid()
 {
 	float r;
@@ -182,11 +201,12 @@ static void spawn_asteroid()
 	else
 		r = ASTEROID_LARGE;
 
-	entity_t *e = gen_asteroid(r);
+	unsigned id;
+	entity_t *e = gen_asteroid(r, &id);
 	do {
 		e->pos.y = rng_plusminus();
 		e->pos.x = aspect * rng_plusminus();
-	} while (vec2_len(e->pos) < ASTEROID_MIN_DIST);
+	} while (vec2_len(e->pos) < ASTEROID_MIN_DIST || intersecting_any(id));
 	e->vel = (vec2_t) {
 		ASTEROID_VEL_JITTER * rng_plusminus(),
 		ASTEROID_VEL_JITTER * rng_plusminus(),
@@ -246,15 +266,12 @@ static unsigned check_collisions(collision_t *out)
 {
 	unsigned count = 0;
 	for (unsigned i = 0; i < entity_count; ++i) {
-		const entity_t *a = entities + i;
 		for (unsigned j = i + 1; j < entity_count; ++j) {
-			const entity_t *b = entities + j;
-			const float r = vec2_len(vec2_sub(b->pos, a->pos));
-			if (r <= a->radius + b->radius) {
+			if (intersecting(i, j)) {
 				assert(count < MAX_COLLISIONS);
-				collision_t *col = out + count++;
-				col->entities[0] = i;
-				col->entities[1] = j;
+				out[count].entities[0] = i;
+				out[count].entities[1] = j;
+				++count;
 			}
 		}
 	}