Client: toggle to disable ambient NPC population

code/client/CMakeLists.txt

@@ -9,6 +9,7 @@ set(HOGWARTSMP_CLIENT_FILES
     src/core/hooks/localplayer.cpp
     src/core/hooks/pak_mount.cpp
     src/core/hooks/player_controller.cpp
+    src/core/hooks/population.cpp
     src/core/hooks/render_device.cpp
     src/core/hooks/world.cpp
     src/core/modules/human.cpp

code/client/src/core/game_layout.h

@@ -68,6 +68,9 @@ namespace HogwartsMP::Game {
         Aob ulocalplayerCtor; // ULocalPlayer::ULocalPlayer (call site)
         Aob apcCtor;          // APlayerController::APlayerController (call site)
 
+        // --- Ambient population control ---
+        Aob populationManagerTick; // FUN_14316dd90 — no-op to disable all ambient NPC fleshing
+
         Offsets offsets;
     };
 
@@ -116,6 +119,10 @@ namespace HogwartsMP::Game {
         {"LocalPlayer/ULocalPlayer::ULocalPlayer", "E9 ? ? ? ? C3 66 66 66 2E 0F 1F 84 00 00 00 00 00 48 8D 64 24 D8 41 54 F7 1C 24", true},
         {"LocalPlayer/APlayerController::APlayerController", "E9 ? ? ? ? C3 85 C0 3C 88", true},
 
+        // Ambient population — PopulationManagerTick (FUN_14316dd90). No-op disables ambient NPCs.
+        // `80 B9 ? ? 00 00 00` = cmp byte[rcx+0x964],0 (the pause gate). RVA 0x316DD90 is the fallback.
+        {"Population/PopulationManagerTick", "48 89 5C 24 10 57 48 83 EC 40 80 B9 64 09 00 00 00 48 8B FA 48 8B D9", false},
+
         // Offsets
         {/*PersistentLevel*/ 0x30, /*OwningGameInstance*/ 0x330, /*LocalPlayers*/ 0x38},
     };
@@ -155,6 +162,9 @@ namespace HogwartsMP::Game {
         {"LocalPlayer/ULocalPlayer::ULocalPlayer", "E9 ? ? ? ? C3 66 66 66 2E 0F 1F 84 00 00 00 00 00 48 8D 64 24 D8 41 54 F7 1C 24", true},
         {"LocalPlayer/APlayerController::APlayerController", "E9 ? ? ? ? C3 85 C0 3C 88", true},
 
+        // Ambient population — not independently verified for this older build; marked optional.
+        {"Population/PopulationManagerTick", "48 89 5C 24 10 57 48 83 EC 40 80 B9 64 09 00 00 00 48 8B FA 48 8B D9", true},
+
         {/*PersistentLevel*/ 0x30, /*OwningGameInstance*/ 0x320, /*LocalPlayers*/ 0x38},
     };
 

code/client/src/core/hooks/population.cpp

@@ -0,0 +1,66 @@
+#include <utils/safe_win32.h>
+
+#include <MinHook.h>
+#include <utils/hooking/hook_function.h>
+#include <utils/hooking/hooking.h>
+
+#include <logging/logger.h>
+
+#include <atomic>
+#include <cstdint>
+
+#include "../aob_scan.h"
+#include "population.h"
+
+// The whole tiered ambient crowd (BP_Tier3_Character_C / Tier4_Actor / students) is driven by
+// UPopulationManager's per-frame tick, FUN_14316dd90, which ticks its 4 async population jobs.
+// void __fastcall(UPopulationManager* this, FTickCtx*). Address via the game_layout AOB, RVA fallback.
+
+namespace HogwartsMP::Core::Hooks {
+    namespace {
+        constexpr uintptr_t kPopTick_RVA = 0x316DD90; // FUN_14316dd90 fallback (Steam build 20773316)
+
+        using PopTick_t = void(__fastcall *)(void *, void *);
+        PopTick_t s_orig = nullptr;
+
+        // Default OFF (no-op the tick from boot) => areas load EMPTY.
+        // Server owners can flip to ON for vanilla via SetAmbientPopulation.
+        std::atomic<bool> s_enabled{false}; // true = vanilla population; false = no ambient NPCs
+
+        auto Log() {
+            return Framework::Logging::GetLogger("NpcLab");
+        }
+
+        void __fastcall PopTick_Hook(void *mgr, void *tickCtx) {
+            if (!s_enabled.load(std::memory_order_relaxed)) {
+                return; // skip the population tick entirely -> no flesh
+            }
+            s_orig(mgr, tickCtx);
+        }
+    } // namespace
+
+    void SetAmbientPopulation(bool enabled) {
+        s_enabled.store(enabled, std::memory_order_relaxed);
+        Log()->info("AmbientPopulation: {}", enabled ? "ON (vanilla NPCs)" : "OFF (no ambient NPCs)");
+    }
+
+    void ToggleAmbientPopulation() {
+        SetAmbientPopulation(!s_enabled.load(std::memory_order_relaxed));
+    }
+
+    bool IsAmbientPopulationEnabled() {
+        return s_enabled.load(std::memory_order_relaxed);
+    }
+} // namespace HogwartsMP::Core::Hooks
+
+static InitFunction init([]() {
+    using namespace HogwartsMP::Core::Hooks;
+    auto *target = HogwartsMP::Core::AobFirst(HogwartsMP::Game::gLayout.populationManagerTick);
+    if (!target) {
+        // AOB miss/ambiguous — fall back to the pinned RVA for the known build.
+        target = reinterpret_cast<void *>(reinterpret_cast<uintptr_t>(GetModuleHandle(nullptr)) + kPopTick_RVA);
+    }
+    const MH_STATUS st = MH_CreateHook(target, reinterpret_cast<LPVOID>(&PopTick_Hook), reinterpret_cast<void **>(&s_orig));
+    Framework::Logging::GetLogger("NpcLab")->info("AmbientPopulation: hooked PopulationManagerTick @ 0x{:x} status {} (default {})",
+        reinterpret_cast<uintptr_t>(target), static_cast<int>(st), IsAmbientPopulationEnabled() ? "ON" : "OFF");
+}, "AmbientPopulation");

code/client/src/core/hooks/population.h

@@ -0,0 +1,13 @@
+#pragma once
+
+// Ambient population control. Toggles the game's whole ambient-NPC ("Hobo"/Tier crowd) system on/off by
+// no-oping UPopulationManager's per-frame tick. With it OFF, the manager never requests flesh, so
+// NPCs are never spawned.
+
+namespace HogwartsMP::Core::Hooks {
+    // enabled=true => vanilla ambient population; false => no ambient NPCs. Default ON.
+    // Exposed so a console command / scripting builtin can let server owners flip it.
+    void SetAmbientPopulation(bool enabled);
+    void ToggleAmbientPopulation();
+    bool IsAmbientPopulationEnabled();
+} // namespace HogwartsMP::Core::Hooks

code/client/src/core/states/session_connected.cpp

@@ -4,6 +4,7 @@
 #include <utils/states/machine.h>
 
 #include "core/application.h"
+#include "core/hooks/population.h"
 
 namespace HogwartsMP::Core::States {
     SessionConnectedState::SessionConnectedState() {}

code/client/src/core/states/session_offline_debug.cpp

@@ -5,6 +5,7 @@
 #include <utils/states/machine.h>
 
 #include "../application.h"
+#include "../hooks/population.h"
 
 namespace HogwartsMP::Core::States {
     SessionOfflineDebugState::SessionOfflineDebugState() {}