10 SDL_Surface *load_image(char *filename);
13 // 2 sets of sprites, sorted by position
14 static Sprite **sprites[2] = { NULL, NULL };
16 // which set are we using?
19 // size of squares into which sprites are sorted.
20 static int grid_size = 0;
22 // screen size in grid squares.
23 static int gw = 0, gh = 0;
25 // lists of free sprites, by type.
26 Sprite *free_sprites[N_TYPES];
34 uint32_t bits = 0, bit, *p;
37 if(s->image->format->BytesPerPixel != 2) {
38 fprintf(stderr, "get_shape(): not a 16-bit image!\n");
42 s->w = s->image->w; s->h = s->image->h;
43 grid_size = max(grid_size, max(s->w, s->h));
44 s->mask_w = ((s->w+31)>>5);
45 s->mask = malloc(s->mask_w*s->h*sizeof(uint32_t));
47 fprintf(stderr, "get_shape(): can't allocate bitmask.\n");
51 SDL_LockSurface(s->image);
52 px = s->image->pixels;
53 transp = s->image->format->colorkey;
55 for(y=0; y<s->image->h; y++) {
57 for(x=0; x<s->image->w; x++) {
58 if(!bit) { bits = 0; bit = 0x80000000; }
59 if(*px++ != transp) { bits |= bit; s->area++; }
61 if(!bit || x == s->image->w - 1) { *(p++) = bits; }
63 px = (uint16_t *) ((uint8_t *) px + s->image->pitch - 2*s->image->w);
65 SDL_UnlockSurface(s->image);
70 load_sprite(Sprite *s, char *filename)
72 s->image = load_image(filename);
73 if(s->image) get_shape(s);
90 grid_size = grid_size * 3 / 2;
91 gw = (XSIZE-1 + 2*grid_size) / grid_size;
92 gh = (YSIZE-1 + 2*grid_size) / grid_size;
94 sprites[0] = malloc(2 * gw * gh * sizeof(Sprite *));
95 sprites[1] = (void *)sprites[0] + gw * gh * sizeof(Sprite *);
97 fprintf(stderr, "init_sprites(): can't allocate grid squares.\n");
100 memset(sprites[0], 0, 2 * gw * gh * sizeof(Sprite *));
104 static inline Sprite **
105 square(int x, int y, int set)
107 int b = (x+grid_size)/grid_size + gw*((y+grid_size)/grid_size);
108 return &sprites[set][b];
112 add_sprite(Sprite *s)
114 insert_sprite(square(s->x, s->y, set), s);
118 move_sprite(Sprite *s)
121 s->x += (s->dx - screendx)*t_frame;
122 s->y += (s->dy - screendy)*t_frame;
126 sort_sprite(Sprite *s)
128 // clip it, or sort it into the other set of sprites.
129 if(s->x + s->w < 0 || s->x >= XSIZE
130 || s->y + s->h < 0 || s->y >= YSIZE) {
131 insert_sprite(&free_sprites[s->type], s);
133 } else insert_sprite(square(s->x, s->y, 1-set), s);
142 // Move all the sprites (position and set)
143 for(sq=0; sq<gw*gh; sq++) {
144 head=&sprites[set][sq];
146 Sprite *s = remove_sprite(head);
147 move_sprite(s); sort_sprite(s);
150 set = 1-set; // switch to other set of sprites.
155 line_collide(int xov, unsigned bit, uint32_t *amask, uint32_t *bmask)
157 int i, words = (xov-1) >> 5;
160 for(i=0; i<words; i++) {
161 abits = *amask++ << bit;
162 abits |= *amask >> (32-bit);
163 if(abits & *bmask++) return true;
165 abits = *amask << bit;
166 if(abits & *bmask) return true;
172 mask_collide(int xov, int yov, Sprite *a, Sprite *b)
175 int xoffset = a->w - xov;
176 int word = xoffset >> 5, bit = xoffset & 31;
177 uint32_t *amask = a->mask, *bmask = b->mask;
180 amask = a->mask + ((a->h - yov) * a->mask_w) + word;
185 bmask = b->mask + ((b->h - yov) * b->mask_w) + word;
188 for(y=0; y<yov; y++) {
189 if(line_collide(xov, bit, amask, bmask)) return 1;
190 amask += a->mask_w; bmask += b->mask_w;
197 collide(Sprite *a, Sprite *b)
199 int dx, dy, xov, yov;
201 if(a->type < 0 || b->type < 0) return false;
203 if(b->x < a->x) { Sprite *tmp = a; a = b; b = tmp; }
208 xov = max(min(a->w - dx, b->w), 0);
210 if(dy >= 0) yov = max(min(a->h - dy, b->h), 0);
211 else yov = -max(min(b->h - -dy, a->h), 0);
213 if(xov == 0 || yov == 0) return false;
214 else return mask_collide(xov, yov, a, b);
222 for(i=0; i<gw*gh; i++)
223 for(a=sprites[set][i]; a; a=a->next)
224 for(b=a->next; b; b=b->next)
225 if(collide(a, b)) do_collision(a, b);
229 hit_in_square(Sprite *r, Sprite *s)
232 if(collide(r, s)) break;
243 l = (s->x + grid_size) / grid_size;
244 r = (s->x + s->w + grid_size) / grid_size;
245 t = (s->y + grid_size) / grid_size;
246 b = (s->y + s->h + grid_size) / grid_size;
247 sq = &sprites[set][l + t*gw];
249 if((c = hit_in_square(*sq, s))) return c;
250 if(l > 0 && (c = hit_in_square(*(sq-1), s))) return c;
251 if(t > 0 && (c = hit_in_square(*(sq-gw), s))) return c;
252 if(l > 0 && t > 0 && (c = hit_in_square(*(sq-1-gw), s))) return c;
255 if((c = hit_in_square(*(sq+1), s))) return c;
256 if(t > 0 && hit_in_square(*(sq+1-gw), s)) return c;
259 if((c = hit_in_square(*(sq+gw), s))) return c;
260 if(l > 0 && (c = hit_in_square(*(sq-1+gw), s))) return c;
262 if(r > l && b > t && (c = hit_in_square(*(sq+1+gw), s))) return c;
267 pixel_collide(Sprite *s, int x, int y)
271 if(x < s->x || y < s->y || x >= s->x + s->w || y >= s->y + s->h) return 0;
273 x -= s->x; y -= s->y;
274 pmask = 0x80000000 >> (x&0x1f);
275 return s->mask[(y*s->mask_w) + (x>>5)] & pmask;
279 pixel_hit_in_square(Sprite *r, float x, float y)
281 for(; r; r=r->next) {
282 if(pixel_collide(r, x, y)) return 1;
288 pixel_collides(float x, float y)
293 l = (x + grid_size) / grid_size; t = (y + grid_size) / grid_size;
294 sq = &sprites[set][l + t*gw];
295 if(pixel_hit_in_square(*sq, x, y)) return true;
296 if(l > 0 && pixel_hit_in_square(*(sq-1), x, y)) return true;
297 if(t > 0 && pixel_hit_in_square(*(sq-gw), x, y)) return true;
298 if(l > 0 && t > 0 && pixel_hit_in_square(*(sq-1-gw), x, y)) return true;
304 sprite_mass(Sprite *s)
306 if(s->type == SHIP) return s->area;
307 else if(s->type == ROCK) return 3*s->area;
312 bounce(Sprite *a, Sprite *b)
318 // (x, y) is unit vector pointing from A's center to B's center.
319 x = (b->x + b->w / 2) - (a->x + a->w / 2);
320 y = (b->y + b->h / 2) - (a->y + a->h / 2);
321 n = sqrt(x*x + y*y); x /= n; y /= n;
323 // velocities along (x, y), or 0 if already moving away.
324 va = max(x*a->dx + y*a->dy, 0);
325 vb = min(x*b->dx + y*b->dy, 0);
328 ma = sprite_mass(a); mb = sprite_mass(b);
329 if(ma && mb) mr = mb/ma; else mr = 1;
331 a->dx += x*(mb*vb - ma*va)/ma; a->dy += y*(mb*vb - ma*va)/ma;
332 b->dx += x*(ma*va - mb*vb)/mb; b->dy += y*(ma*va - mb*vb)/mb;