Add entity physics

game/systems/s_entity.c

@@ -143,6 +143,53 @@ void entityUpdateKinematic(ecs_iter_t *it) {
         position[i] = Vector2Add(position[i], Vector2Scale(velocity[i], dt));
     }
 }
+void entityUpdatePhysics(ecs_iter_t *it) {
+    Game *game = ecs_singleton_get_mut(ECS, Game);
+    Position *position = ecs_field(it, Position, 1);
+    HitBox *hitbox = ecs_field(it, HitBox, 2);
+    Velocity *velocity = ecs_field(it, Velocity, 3);
+    SpatialGridID *spatialID = ecs_field(it, SpatialGridID, 4);
+
+    f32 dt = it->delta_time;
+
+    for (i32 i = 0; i < it->count; i++) {
+        // Only update "stationary" entities
+        bool stationary = Vector2Length(velocity[i]) <= 0.2f;
+        Rectangle bounds = entityTransformHitBox(position[i], hitbox[i]);
+        BzSpatialGridIter spatialIt = bzSpatialGridIter(game->entityGrid, bounds.x, bounds.y,
+                                                 bounds.width, bounds.height);
+        Vector2 dir = Vector2Zero();
+        f32 slowDown = 0.0f;
+        while (bzSpatialGridQueryNext(&spatialIt)) {
+            ecs_entity_t other = *(ecs_entity_t *) spatialIt.data;
+            if (other == it->entities[i])
+                continue;
+            Position otherPos;
+            Rectangle otherBounds;
+            if (!entityGetHitBox(other, &otherPos, &otherBounds))
+                continue;
+
+            if (!CheckCollisionRecs(bounds, otherBounds)) {
+                continue;
+            }
+            slowDown += 0.1f;
+            Position dif = Vector2Subtract(otherPos, position[i]);
+            //dif = Vector2Normalize(dif);
+            dir = Vector2Add(dir, dif);
+        }
+
+        if (stationary) {
+            dir = Vector2Normalize(dir);
+            dir = Vector2Scale(dir, 40);
+            velocity[i] = Vector2Subtract(velocity[i], dir);
+        }
+
+        slowDown = BZ_MIN(slowDown, 0.85f);
+        if (!stationary && slowDown > 0.0f) {
+            velocity[i] = Vector2Scale(velocity[i], 1 - slowDown);
+        }
+    }
+}
 
 void entityMoveToTarget(ecs_iter_t *it) {
     Position *position = ecs_field(it, Position, 1);