git.itanic.dy.fi Git - sdl-planets/blob - planet.c

   1 #include <math.h>
   2
   3 #include "random.h"
   4 #include "planet.h"
   5 #include "utils.h"
   6
   7 struct quadtree_ops planet_ops;
   8
   9 static void putpixel(struct SDL_Surface *screen, const int x, const int y,
  10                      const unsigned char r, const unsigned char g,
  11                      const unsigned char b)
  12 {
  13         int offset = y * screen->pitch + x * 4;
  14         unsigned char *buf = screen->pixels;
  15
  16         buf[offset++] = b;
  17         buf[offset++] = g;
  18         buf[offset]   = r;
  19 }
  20
  21 static void reshape_planet(struct planet *p)
  22 {
  23         p->radius = pow(p->mass / 100, 1 / 3.0);
  24 }
  25
  26 void init_planet(struct planet *p)
  27 {
  28         memset(p, 0, sizeof(*p));
  29         reshape_planet(p);
  30         p->r = get_random() % 256;
  31         p->g = get_random() % 256;
  32         p->b = get_random() % 256;
  33
  34         INIT_LIST_HEAD(&p->list);
  35         init_quadtree(&p->tree);
  36 }
  37
  38 /**
  39  * setup_planet - set the planet on a "solarsystem"
  40  * @p:          pointer to struct planet to set up
  41  * @mass:       mass of the planet to set up
  42  * @total_mass: total mass of the system
  43  * @radius:     maximum radius of the system
  44  */
  45
  46 static void setup_planet(struct planet *p, double mass, double total_mass,
  47                          double radius)
  48 {
  49         double angle = M_PI * 2 * get_random_double();
  50         double velocity;
  51         double distance;
  52
  53         distance = radius * pow(get_random_double(), 2);
  54         velocity = sqrt(total_mass / radius);
  55
  56         velocity *= pow(distance / radius, 0.2);
  57
  58         p->pos.x = cos(angle) * distance;
  59         p->pos.y = sin(angle) * distance;
  60
  61         p->speed.x = -sin(angle) * velocity;
  62         p->speed.y = cos(angle) * velocity;
  63
  64         p->mass = mass;
  65
  66         reshape_planet(p);
  67 }
  68
  69 void create_planets(struct planet *p, int num, double total_mass, double radius)
  70 {
  71         int i;
  72         double sum = 0;
  73         struct planet *new_planet;
  74
  75         setup_planet(p,
  76                      total_mass / num * 2 * get_random_double(),
  77                      total_mass,
  78                      radius);
  79
  80         for (i = 0; i < num; i++) {
  81                 new_planet = malloc(sizeof(*new_planet));
  82                 init_planet(new_planet);
  83
  84                 list_add(&new_planet->list, &p->list);
  85
  86                 setup_planet(new_planet,
  87                              total_mass / num * 2 * get_random_double(),
  88                              total_mass,
  89                              radius);
  90
  91                 quadtree_add(&p->tree, &new_planet->tree, &planet_ops);
  92
  93                 sum += new_planet->mass;
  94         }
  95 }
  96
  97 void draw_planet(SDL_Surface *screen, struct planet *p,
  98                  const struct camera *cam)
  99 {
 100         struct vector pos;
 101         float radius = p->radius * cam->zoom;
 102         float r2 = radius * radius;
 103         int x, x_start, y, x_end;
 104
 105         vector_sub(&p->pos, &cam->pos, &pos);
 106         vector_scale(&pos, cam->zoom, &pos);
 107         pos.x += screen->w / 2;
 108         pos.y += screen->h / 2;
 109
 110         y = MAX(pos.y - radius, 0);
 111
 112         if (radius * 2 <= 1) {
 113                 if (pos.x >= 0 && pos.x < screen->w &&
 114                     pos.y >= 0 && pos.y < screen->h)
 115                         putpixel(screen, (int)pos.x, (int)pos.y,
 116                                  p->r, p->g, p->b);
 117                 return;
 118         }
 119
 120         for (; y < MIN(pos.y + radius, screen->h); y++) {
 121                 int offset;
 122                 unsigned char *buf = screen->pixels;
 123                 float y2 = (y - pos.y);
 124
 125                 y2 = sqrt(r2 - y2 * y2);
 126                 x_start = pos.x - y2;
 127                 x_end = pos.x + y2;
 128                 x_start = MAX(0, x_start);
 129                 x_end = MIN(x_end, screen->w);
 130
 131                 offset = y * screen->pitch + x_start * 4;
 132                 for (x = x_start; x < x_end; x++) {
 133                         buf[offset++] = p->b;
 134                         buf[offset++] = p->g;
 135                         buf[offset++] = p->r;
 136                         offset++;
 137                 }
 138         }
 139 }
 140
 141 int gravitize_planets(struct planet *a, struct planet *b, const double time)
 142 {
 143         struct vector distance, sum;
 144         double dist, f, acc;
 145
 146         vector_sub(&a->pos, &b->pos, &distance);
 147
 148         dist = vector_abs(&distance);
 149
 150         /* Return true in case of a collision */
 151         if (dist < (a->radius + b->radius))
 152                 return 1;
 153
 154         vector_div(&distance, dist, &distance);
 155
 156         f = a->mass * b->mass / (dist * dist) * time;
 157
 158         acc = f / b->mass;
 159         vector_scale(&distance, acc, &sum);
 160         vector_add(&b->speed, &sum, &b->speed);
 161
 162         acc = f / a->mass;
 163         vector_scale(&distance, acc, &sum);
 164         vector_sub(&a->speed, &sum, &a->speed);
 165
 166         return 0;
 167 }
 168
 169 /*
 170  * Merge planets a and b into planet a
 171  *
 172  * It is left for the caller to deal with the scrap planet b
 173  */
 174 static void _merge_planets(struct planet *a, struct planet *b)
 175 {
 176         struct vector pa, pb, p;
 177
 178         vector_scale(&a->speed, a->mass, &pa);
 179         vector_scale(&b->speed, b->mass, &pb);
 180         vector_add(&pa, &pb, &p);
 181
 182         if (a->mass < b->mass)
 183                 a->pos = b->pos;
 184
 185         a->mass += b->mass;
 186         reshape_planet(a);
 187         vector_div(&p, a->mass, &a->speed);
 188 }
 189
 190 /*
 191  * Merge planets a and b into a the new planet a, which pointer is
 192  * returned to the caller. Planet b is removed from the linked list
 193  * and it's memory is freed. The merged planet will retain in the
 194  * list.
 195  */
 196 struct planet *merge_planets(struct planet *a, struct planet *b)
 197 {
 198         _merge_planets(a, b);
 199
 200         list_del(&b->list);
 201         quadtree_del(&b->tree, &planet_ops);
 202
 203         free(b);
 204         return a;
 205 }
 206
 207 static int planet_search_when_moving(struct quadtree *node,
 208                                      struct quadtree_iterator *itr)
 209 {
 210         struct planet *p = tree_to_planet(node);
 211         struct planet_search_iterator *it = qt_itr_to_planet_itr(itr);
 212         int direction = 0, i;
 213         int up = 0, left = 0, right = 0, down = 0;
 214
 215         for (i = 0; i < 2; i++) {
 216                 if (it->limit[i].x < p->pos.x)
 217                         left = 1;
 218                 else
 219                         right = 1;
 220                 if (it->limit[i].y < p->pos.y)
 221                         up = 1;
 222                 else
 223                         down = 1;
 224         }
 225
 226         if (left || up)
 227                 direction |= QUADTREE_UPLEFT;
 228         if (right || up)
 229                 direction |= QUADTREE_UPRIGHT;
 230         if (left || down)
 231                 direction |= QUADTREE_DOWNLEFT;
 232         if (right || down)
 233                 direction |= QUADTREE_DOWNRIGHT;
 234         if ((left && right) || (up && down))
 235                 direction |= QUADTREE_SELF;
 236
 237         return direction;
 238 }
 239
 240 void planet_move_iterator(struct quadtree *node, struct quadtree_iterator *it)
 241 {
 242         struct quadtree *parent;
 243
 244         parent = quadtree_del(node, &planet_ops);
 245         quadtree_add(parent, node, &planet_ops);
 246 }
 247
 248 struct planet *move_planet(struct planet *p, const double time)
 249 {
 250         struct vector tmp, new_pos;
 251         struct quadtree *parent, *tree_parent;
 252         struct planet *pa;
 253         struct planet_search_iterator it;
 254
 255         int modify = 0;
 256
 257         vector_scale(&p->speed, time, &tmp);
 258         vector_add(&p->pos, &tmp, &new_pos);
 259
 260         /* Check if we have crossed any of the parents */
 261         parent = p->tree.parent;
 262         while (parent) {
 263                 pa = tree_to_planet(parent);
 264                 if (p->pos.x < pa->pos.x && new_pos.x > pa->pos.x)
 265                         modify = 1;
 266                 if (p->pos.x > pa->pos.x && new_pos.x < pa->pos.x)
 267                         modify = 1;
 268                 if (p->pos.y < pa->pos.y && new_pos.y > pa->pos.y)
 269                         modify = 1;
 270                 if (p->pos.y > pa->pos.y && new_pos.y < pa->pos.y)
 271                         modify = 1;
 272
 273                 if (!modify) {
 274                         parent = parent->parent;
 275                         continue;
 276                 }
 277
 278                 tree_parent = quadtree_del(&p->tree, &planet_ops);
 279                 p->pos = new_pos;
 280                 quadtree_add(tree_parent, &p->tree, &planet_ops);
 281                 return tree_to_planet(tree_parent);
 282         }
 283
 284         /*
 285          * Now, search the subtree for any crossed children and move
 286          * them into correct place within the tree.
 287          */
 288         it.qt_iterator.head = &p->tree;
 289         it.limit[0] = p->pos;
 290         it.limit[1] = new_pos;
 291         it.qt_iterator.direction = planet_search_when_moving;
 292         it.qt_iterator.callback = planet_move_iterator;
 293         walk_quadtree(&it.qt_iterator);
 294
 295         p->pos = new_pos;
 296
 297         return tree_to_planet(quadtree_find_parent(&p->tree));
 298 }
 299
 300 void print_planet(const struct planet *p)
 301 {
 302         printf("pos: (%f,%f), speed: (%f,%f), mass: %f, radius %f\n",
 303                p->pos.x, p->pos.y, p->speed.x, p->speed.y, p->mass, p->radius);
 304 }
 305
 306 int planet_spatial_compare(struct quadtree *ta, struct quadtree *tb)
 307 {
 308         struct planet *a, *b;
 309         int up, left;
 310         a = tree_to_planet(ta);
 311         b = tree_to_planet(tb);
 312
 313         up = b->pos.y < a->pos.y;
 314         left = b->pos.x < a->pos.x;
 315
 316         if (up && left)
 317                 return 0;
 318         if (up && !left)
 319                 return 1;
 320         if (left)
 321                 return 2;
 322         return 3;
 323 }
 324
 325 int planet_search_rectangular(struct quadtree *node,
 326                               struct quadtree_iterator *itr)
 327 {
 328         struct planet_search_iterator *it = qt_itr_to_planet_itr(itr);
 329         struct planet *p = tree_to_planet(node);
 330         int direction = 0, i;
 331         int up = 0, left = 0, right = 0, down = 0;
 332
 333         for (i = 0; i < 2; i++) {
 334                 if (it->limit[i].x < p->pos.x)
 335                         left = 1;
 336                 else
 337                         right = 1;
 338                 if (it->limit[i].y < p->pos.y)
 339                         up = 1;
 340                 else
 341                         down = 1;
 342         }
 343
 344         if (left && up)
 345                 direction |= QUADTREE_UPLEFT;
 346         if (right && up)
 347                 direction |= QUADTREE_UPRIGHT;
 348         if (left && down)
 349                 direction |= QUADTREE_DOWNLEFT;
 350         if (right && down)
 351                 direction |= QUADTREE_DOWNRIGHT;
 352         if (direction == (QUADTREE_UPLEFT | QUADTREE_UPRIGHT |
 353                           QUADTREE_DOWNLEFT | QUADTREE_DOWNRIGHT))
 354                 direction |= QUADTREE_SELF;
 355
 356         return direction;
 357 }
 358
 359 void planet_draw_iterator(struct quadtree *node, struct quadtree_iterator *it)
 360 {
 361         struct planet *p = tree_to_planet(node);
 362         struct planet_search_iterator *i = qt_itr_to_planet_itr(it);
 363
 364         draw_planet(i->screen, p, i->cam);
 365 }
 366
 367 static void planet_recalculate_stats(struct quadtree *node)
 368 {
 369         struct planet *p = tree_to_planet(node), *c;
 370         struct vector vect;
 371         double dist;
 372         int i;
 373
 374         p->tree_area = 0;
 375         p->tree_mass = p->mass;
 376
 377         for (i = 0; i < 4; i++) {
 378                 if (!node->child[i])
 379                         continue;
 380
 381                 c = tree_to_planet(node->child[i]);
 382                 p->tree_mass += c->tree_mass;
 383
 384                 vector_sub(&p->pos, &c->pos, &vect);
 385                 dist = vector_abs(&vect);
 386                 dist += c->tree_area;
 387                 p->tree_area = MAX(p->tree_area, dist);
 388         }
 389 }
 390
 391 struct quadtree_ops planet_ops = {
 392         .compare = planet_spatial_compare,
 393         .recalculate_stats = planet_recalculate_stats,
 394 };
 395