MMO Entity Tick Server

1#include "bs9/scheduler.hpp"
2 
3#include <algorithm>
4#include <cmath>
5#include <limits>
6 
7namespace bs9 {
8 
9float distance_sq(const Vec3& a, const Vec3& b) noexcept {
10  const float dx = a.x - b.x;
11  const float dy = a.y - b.y;
12  const float dz = a.z - b.z;
13  return dx * dx + dy * dy + dz * dz;
14}
15 
16const char* tier_name(Tier t) noexcept {
17  switch (t) {
18    case Tier::Hot:
19      return "hot";
20    case Tier::Warm:
21      return "warm";
22    case Tier::Cool:
23      return "cool";
24    case Tier::Cold:
25      return "cold";
26    case Tier::Frozen:
27      return "frozen";
28    default:
29      return "?";
30  }
31}
32 
33void EntityScheduler::set_entities(std::vector<Entity> entities) {
34  entities_ = std::move(entities);
35 
36  tiers_.assign(entities_.size(), Tier::Frozen);
37  next_due_.assign(entities_.size(), 0);
38  phase_.resize(entities_.size());
39 
40  // A fixed per-entity phase offset is what keeps a 30-frame tier from
41  // updating all of its entities on the same frame.
42  for (std::size_t i = 0; i < entities_.size(); ++i) {
43    phase_[i] = static_cast<std::uint32_t>(entities_[i].id * 2654435761u >> 16);
44  }
45 
46  deferred_.clear();
47  queued_.assign(entities_.size(), 0);
48  retier();
49 
50  // Stagger the first update of every entity across its interval, otherwise
51  // the whole world comes due on frame 0 and again every `interval` frames.
52  for (std::size_t i = 0; i < entities_.size(); ++i) {
53    const std::uint32_t interval =
54        cfg_.intervals[static_cast<std::size_t>(tiers_[i])];
55    next_due_[i] = interval > 1 ? phase_[i] % interval : 0;
56  }
57}
58 
59void EntityScheduler::set_players(std::vector<Vec3> players) {
60  players_ = std::move(players);
61}
62 
63Tier EntityScheduler::classify(const Entity& e) const {
64  if (e.pinned || e.activity >= cfg_.activity_promote) return Tier::Hot;
65  if (players_.empty()) return Tier::Frozen;
66 
67  float best = std::numeric_limits<float>::max();
68  for (const auto& p : players_) {
69    best = std::min(best, distance_sq(e.position, p));
70  }
71 
72  // Activity shrinks the effective distance: a moving vehicle is treated as
73  // if it were closer than it is, so it does not go dormant mid-manoeuvre.
74  const float scale = 1.0f - 0.5f * std::clamp(e.activity, 0.f, 1.f);
75  const float d = std::sqrt(best) * scale;
76 
77  if (d <= cfg_.hot_radius) return Tier::Hot;
78  if (d <= cfg_.warm_radius) return Tier::Warm;
79  if (d <= cfg_.cool_radius) return Tier::Cool;
80  if (d <= cfg_.cold_radius) return Tier::Cold;
81  return Tier::Frozen;
82}
83 
84void EntityScheduler::retier() {
85  for (std::size_t i = 0; i < entities_.size(); ++i) {
86    const Tier before = tiers_[i];
87    const Tier now = classify(entities_[i]);
88    if (now == before) continue;
89    tiers_[i] = now;
90 
91    if (now < before) {
92      // Promotion takes effect immediately — an entity that just became
93      // relevant must not wait out the rest of a 30-frame interval.
94      next_due_[i] = static_cast<std::uint32_t>(frame_);
95    } else {
96      // Demotion re-phases the entity so a whole cohort dropping to a slow
97      // tier together does not then come due together.
98      const std::uint32_t interval =
99          cfg_.intervals[static_cast<std::size_t>(now)];
100      next_due_[i] = static_cast<std::uint32_t>(