deteministicish physics

src/game.c

@@ -12,6 +12,8 @@
 #define MAX_ROPE_GRAB_LEN 80000
 #define MIN_PHYSICS_STEP 2.0
 
+#define TIMESTEP_LENGTH 2.0
+
 #define BREAKPOINT *(int *)0 = 1;
 
 GlobWorld world;
@@ -30,6 +32,9 @@ int get_floor_ceiling();
 
 struct sg_times_list save_times_lst;
 
+struct timespec last_tick;
+double time_remaining = 0;
+
 /* array of all the things in the world and their kinds */
 //world_thing *world;
 
@@ -1216,41 +1221,13 @@ void advance_thing(Body * thing) {
         return;
     }
 
+    double time_delta = TIMESTEP_LENGTH;
+
     Vect translation;
     Vect friction;
     translation.x = translation.y = 0;
     int numcols = 0;
 
-    // get time delta
-    struct timespec now = get_now();
-    clock_gettime(CLOCK_MONOTONIC, &now);
-    if (now.tv_nsec >= 1000000000) {
-        now.tv_nsec -= 1000000000;
-    }
-
-    double time_delta = now.tv_nsec - thing->last_advance_time.tv_nsec;
-
-    if (now.tv_nsec < thing->last_advance_time.tv_nsec) {
-        time_delta = now.tv_nsec - (thing->last_advance_time.tv_nsec - 1000000000);
-    }
-    time_delta *= 0.000001; // convert to ms from ns
-
-
-    // cap the time delta: simulatino will slow down
-//    printf("delta: %f\n", time_delta);
-    if (time_delta > 19) {
-        printf("ERROR too slow: %f\n", time_delta);
-        time_delta = 19;
-        quality--;
-    }
-
-    if (time_delta < MIN_PHYSICS_STEP) {
-        SDL_Delay(MIN_PHYSICS_STEP);
-        advance_thing(thing); 
-        return;
-    }
-    thing->last_advance_time = now;
-
     // collisions
     if ((numcols = process_collisions(thing, &translation))) {
         /*double check = vect_scalar_projection(translation, thing->vel);*/
@@ -1483,37 +1460,52 @@ void get_projectile(Projectile** proj) {
 void advance_things(void) {
     int numcols;
     Vect translation;
-    for (int i = 0; i < world.items.size; i++) {
-        switch (world.get(i).kind) {
-            case PLAYER_W :
-                advance_thing((world.get(i).player->physics));
-                continue;
-            case STATIC_WALL_W:
-                advance_thing(world.get(i).wall->physics);
-                continue;
-            case FLOOR:
-                continue;
-                /*for (int k = 0; k < world.get(i).floor->numPolys; k++) {*/
-                    /*advance_thing(world.get(i).floor->polys[k].physics);*/
-                /*}*/
-                /*break;*/
-            case CEILING:
-                continue;
-                /*for (int k = 0; k < world.get(i).floor->numPolys; k++) {*/
-                    /*advance_thing(world.get(i).floor->polys[k].physics);*/
-                /*}*/
-                /*break;*/
-            case PROJECTILE:
-                if ((numcols = process_collisions(world.get(i).projectile->physics,
-                                &translation))) {
-                    world.get(i).projectile->on_collision(world.get(i).projectile);
-                }
-                world.get(i).projectile->on_step(world.get(i).projectile);
-                continue;
-            default:
-                continue;
-        }
+
+    /* update the timer */
+    struct timespec now = get_now();
+    double time_delta = now.tv_nsec - last_tick.tv_nsec;
+
+    if (now.tv_nsec < last_tick.tv_nsec) {
+        time_delta = now.tv_nsec - (last_tick.tv_nsec - 1000000000);
     }
+    time_delta *= 0.000001; // convert to ms from ns
+    time_remaining += time_delta;
+    last_tick = now;
+
+    while (time_remaining > TIMESTEP_LENGTH) {
+        time_remaining -= TIMESTEP_LENGTH;
+        for (int i = 0; i < world.items.size; i++) {
+            switch (world.get(i).kind) {
+                case PLAYER_W :
+                    advance_thing((world.get(i).player->physics));
+                    continue;
+                case STATIC_WALL_W:
+                    advance_thing(world.get(i).wall->physics);
+                    continue;
+                case FLOOR:
+                    continue;
+                    /*for (int k = 0; k < world.get(i).floor->numPolys; k++) {*/
+                        /*advance_thing(world.get(i).floor->polys[k].physics);*/
+                    /*}*/
+                    /*break;*/
+                case CEILING:
+                    continue;
+                    /*for (int k = 0; k < world.get(i).floor->numPolys; k++) {*/
+                        /*advance_thing(world.get(i).floor->polys[k].physics);*/
+                    /*}*/
+                    /*break;*/
+                case PROJECTILE:
+                    if ((numcols = process_collisions(world.get(i).projectile->physics,
+                                    &translation))) {
+                        world.get(i).projectile->on_collision(world.get(i).projectile);
+                    }
+                    world.get(i).projectile->on_step(world.get(i).projectile);
+                    continue;
+                default:
+                    continue;
+            }
+        }
+    }   
 }
 
 bool unique_world_kind(enum world_thing_kind k) {
@@ -1742,6 +1734,7 @@ int step(void) {
         game_paused = 1;
     }
 
+
     if (player.physics->position.x > world.uniques_index[ROOM_W]->room
             ->floor.items[world.uniques_index[ROOM_W]->room->floor.numItems - 1]->position.x) {
         return 1;
@@ -1756,6 +1749,8 @@ int step(void) {
         if (in_game) {
             advance_things();
         }
+    } else {
+        last_tick = get_now();
     }
 
     return 0;

src/main.c

@@ -48,24 +48,29 @@ void redraw(struct SDL_Renderer * ren) {
     SDL_RenderPresent(ren);
 }
 
+
+void godophysics(void) {
+    if (step())  {
+        // display end level screen
+        in_game = false;
+        game_paused = true;
+        SDL_Delay(300);
+        SDL_SemWait(resume);
+        add_time(level_time);
+
+        SDL_LockMutex(player.physics->lock);
+        next_level();
+        in_game = true;
+        SDL_UnlockMutex(player.physics->lock);
+        SDL_Delay(1000);
+        game_paused = false;
+    }
+}
+
 int physics_loop(void *ptr) {
     game_paused = 1;
     while (1) {
-        if (step())  {
-            // display end level screen
-            in_game = false;
-            game_paused = true;
-            SDL_Delay(300);
-            SDL_SemWait(resume);
-            add_time(level_time);
-
-            SDL_LockMutex(player.physics->lock);
-            next_level();
-            in_game = true;
-            SDL_UnlockMutex(player.physics->lock);
-            SDL_Delay(1000);
-            game_paused = 0;
-        }
+        godophysics();
     }
 }
 
@@ -77,9 +82,9 @@ int game(void) {
 
     logwrite(INFO, "Starting\n");
     SDL_Window * win = make_window();
-    SDL_Renderer * ren = SDL_CreateRenderer(win, -1, SDL_RENDERER_ACCELERATED);
+    SDL_Renderer * ren = SDL_CreateRenderer(win, -1, SDL_RENDERER_ACCELERATED
+            | SDL_RENDERER_PRESENTVSYNC);
     SDL_SetRenderDrawBlendMode(ren, SDL_BLENDMODE_BLEND);
-//            | SDL_RENDERER_PRESENTVSYNC);
 
     queue_for_cleanup(win, WINDOW);
     queue_for_cleanup(ren, RENDERER);
@@ -130,8 +135,6 @@ int game(void) {
                     handle_input_event (event);
             }
         }
-        /* Redraw Screen */
-//        step(10);
 
         if (!in_game) {
             draw_end_screen(ren);