sort hit events by dt to prevent out of order bullet hit processing

src/entity.h

@@ -229,7 +229,6 @@ struct entity {
     struct v2 bullet_src_pos;
     struct v2 bullet_src_dir;
     f32 bullet_impulse;
-    b32 bullet_has_hit;  /* Has the bullet hit a target this tick */
 
     /* ====================================================================== */
     /* Testing */

src/game.c

@@ -944,14 +944,38 @@ INTERNAL void game_update(struct game_cmd_array game_cmds)
     /* ========================== *
      * Respond to hit events
      * ========================== */
+    {
+        struct temp_arena temp = arena_temp_begin(scratch.arena);
 
+        /* Sort hit events by dt (to ensure early time of impact collisions are processed first) */
+        struct phys_hit_event_node *first_sorted = NULL;
         for (u64 entity_index = 0; entity_index < store->reserved; ++entity_index) {
             struct entity *ent = &store->entities[entity_index];
             if (!entity_is_valid_and_active(ent)) continue;
             if (!entity_has_prop(ent, ENTITY_PROP_HIT_EVENT)) continue;
+            struct phys_hit_event *e = &ent->hit_event;
+            struct phys_hit_event_node *next = first_sorted;
+            struct phys_hit_event_node *prev = NULL;
+            while (next) {
+                if (e->dt < next->e->dt) {
+                    break;
+                }
+                prev = next;
+                next = next->next;
+            }
+            struct phys_hit_event_node *n = arena_push_zero(temp.arena, struct phys_hit_event_node);
+            n->e = e;
+            n->next = next;
+            if (prev) {
+                prev->next = n;
+            } else {
+                first_sorted = n;
+            }
+        }
 
-        struct phys_hit_event *event = &ent->hit_event;
-
+        /* Process events */
+        for (struct phys_hit_event_node *n = first_sorted; n; n = n->next) {
+            struct phys_hit_event *event = n->e;
             struct entity *e0 = entity_from_handle(store, event->e0);
             struct entity *e1 = entity_from_handle(store, event->e1);
 
@@ -960,22 +984,11 @@ INTERNAL void game_update(struct game_cmd_array game_cmds)
                 if (entity_has_prop(e0, ENTITY_PROP_BULLET) || entity_has_prop(e1, ENTITY_PROP_BULLET)) {
                     struct entity *bullet = entity_has_prop(e0, ENTITY_PROP_BULLET) ? e0 : e1;
                     struct entity *target = e0 == bullet ? e1 : e0;
-                if (!bullet->bullet_has_hit) {
-                    bullet->bullet_has_hit = true;
                     (UNUSED)bullet;
                     (UNUSED)target;
-    #if 0
-                    {
-                        /* Set bullet position to hit position */
-                        struct xform xf = entity_get_xform(bullet);
-                        xf.og = event->point;
-                        entity_set_xform(bullet, xf);
-                        /* Release after publish so user sees bullet in final postiion */
-                        entity_enable_prop(bullet, ENTITY_PROP_RELEASE_AFTER_PUBLISH);
-                    }
-    #else
+
                     entity_enable_prop(bullet, ENTITY_PROP_RELEASE_BEFORE_PUBLISH);
-    #endif
+                    entity_disable_prop(bullet, ENTITY_PROP_ACTIVE);
 
                     /* Create test blood */
                     /* TODO: Remove this */
@@ -992,6 +1005,8 @@ INTERNAL void game_update(struct game_cmd_array game_cmds)
                 }
             }
         }
+
+        arena_temp_end(temp);
     }
 
     /* ========================== *

src/phys.c

@@ -37,7 +37,7 @@ struct phys_startup_receipt phys_startup(void)
  * Contact
  * ========================== */
 
-void phys_create_contacts(struct phys_ctx *ctx)
+void phys_create_contacts(struct phys_ctx *ctx, f32 elapsed_dt)
 {
     u64 tick_id = ctx->tick_id;
     struct entity_lookup *contact_lookup = ctx->contact_lookup;
@@ -121,6 +121,7 @@ void phys_create_contacts(struct phys_ctx *ctx)
                         event->hit_event.e0 = e0->handle;
                         event->hit_event.e1 = e1->handle;
                         event->hit_event.normal = collider_res.normal;
+                        event->hit_event.dt = elapsed_dt;
                         entity_enable_prop(event, ENTITY_PROP_RELEASE_BEFORE_PUBLISH);
                         entity_enable_prop(event, ENTITY_PROP_ACTIVE);
 
@@ -1120,13 +1121,14 @@ void phys_step(struct phys_ctx *ctx, f32 timestep)
             const u32 max_iterations = 16;
             f32 earliest_toi = max_f32(phys_determine_earliest_toi_for_bullets(ctx, step_dt, tolerance, max_iterations), min_toi);
             step_dt = remaining_dt * earliest_toi;
+            remaining_dt -= step_dt;
 #else
             (UNUSED)toi;
             (UNUSED)determine_earliest_toi_for_bullets;
 #endif
         }
 
-        phys_create_contacts(ctx);
+        phys_create_contacts(ctx, timestep - remaining_dt);
         phys_create_mouse_joints(ctx);
 
         phys_prepare_contacts(ctx);
@@ -1153,6 +1155,5 @@ void phys_step(struct phys_ctx *ctx, f32 timestep)
             phys_solve_contacts(ctx, substep_dt, false);  /* Relaxation */
 #endif
         }
-        remaining_dt -= step_dt;
     }
 }

src/phys.h

@@ -25,6 +25,12 @@ struct phys_hit_event {
     struct v2 point;
     struct v2 normal;
     struct v2 vrel;     /* Relative velocity */
+    f32 dt;             /* How much time elapsed in the step when this event occurred (this will equal the physics timestep unless an early time of impact collision occurred) */
+};
+
+struct phys_hit_event_node {
+    struct phys_hit_event *e;
+    struct phys_hit_event_node *next;
 };
 
 /* ========================== *
@@ -91,7 +97,7 @@ struct phys_collision_debug {
     struct xform xf1;
 };
 
-void phys_create_contacts(struct phys_ctx *ctx);
+void phys_create_contacts(struct phys_ctx *ctx, f32 elapsed_dt);
 void phys_prepare_contacts(struct phys_ctx *ctx);
 void phys_warm_start_contacts(struct phys_ctx *ctx);
 void phys_solve_contacts(struct phys_ctx *ctx, f32 dt, b32 apply_bias);