Fix #3589

src/items/powerup.cpp

@@ -526,6 +526,7 @@ void Powerup::hitBonusBox(const ItemState &item_state)
     // (1) The item id
     // (2) The time
     // (3) The position of the kart
+    // (4) An extra random 64bit integer
     // Using (1) means that not all boxes at a certain time for a kart
     // will give the same box. Using (2) means that the item will
     // change over time - even if the next item is displayed, it 
@@ -533,7 +534,8 @@ void Powerup::hitBonusBox(const ItemState &item_state)
     // of the time component it will also be difficult to get the
     // item at the right time. Using (3) adds another cheat-prevention
     // layer: even if a cheater is waiting for the right sequence
-    // of items, if he is overtaken the sequence will change.
+    // of items, if he is overtaken the sequence will change, using (4)
+    // to avoid same item sequence when starting
     //
     // In order to increase the probability of correct client prediction
     // in networking (where there might be 1 or 2 frames difference
@@ -544,7 +546,8 @@ void Powerup::hitBonusBox(const ItemState &item_state)
     // number to spread the random values across the (typically 200)
     // weights used in the PowerupManager - same for the position.
     uint64_t random_number = item_state.getItemId() * 31 +
-        world->getTicksSinceStart() / 10 + position * 23;
+        world->getTicksSinceStart() / 10 + position * 23 +
+        powerup_manager->getRandomSeed();
 
     // Use this random number as a seed of a PRNG (based on the one in 
     // bullet's btSequentialImpulseConstraintSolver) to avoid getting

src/items/powerup_manager.cpp

@@ -43,6 +43,7 @@ PowerupManager* powerup_manager=0;
 /** The constructor initialises everything to zero. */
 PowerupManager::PowerupManager()
 {
+    m_random_seed.store(0);
     for(int i=0; i<POWERUP_MAX; i++)
     {
         m_all_meshes[i] = NULL;

src/items/powerup_manager.hpp

@@ -19,11 +19,13 @@
 #ifndef HEADER_POWERUPMANAGER_HPP
 #define HEADER_POWERUPMANAGER_HPP
 
-#include "utils/no_copy.hpp"
 #include "utils/leak_check.hpp"
+#include "utils/no_copy.hpp"
+#include "utils/types.hpp"
 
 #include "btBulletDynamicsCommon.h"
 
+#include <atomic>
 #include <map>
 #include <string>
 #include <vector>
@@ -151,6 +153,11 @@ private:
     WeightsData m_current_item_weights;
 
     PowerupType   getPowerupType(const std::string &name) const;
+
+    /** Seed for random powerup, for local game it will use a random number,
+     *  for network games it will use the start time from server. */
+    std::atomic<uint64_t> m_random_seed;
+
 public:
     static void unitTesting();
 
@@ -171,6 +178,11 @@ public:
     /** Returns the mesh for a certain powerup.
      *  \param type Mesh type for which the model is returned. */
     irr::scene::IMesh *getMesh(int type) const {return m_all_meshes[type];}
+    // ------------------------------------------------------------------------
+    uint64_t getRandomSeed() const { return m_random_seed.load(); }
+    // ------------------------------------------------------------------------
+    void setRandomSeed(uint64_t seed) { m_random_seed.store(seed); }
+
 };   // class PowerupManager
 
 extern PowerupManager* powerup_manager;

src/network/protocols/client_lobby.cpp

@@ -26,6 +26,7 @@
 #include "guiengine/screen_keyboard.hpp"
 #include "input/device_manager.hpp"
 #include "items/item_manager.hpp"
+#include "items/powerup_manager.hpp"
 #include "karts/kart_properties_manager.hpp"
 #include "modes/linear_world.hpp"
 #include "network/crypto.hpp"
@@ -816,6 +817,7 @@ void ClientLobby::startGame(Event* event)
 {
     World::getWorld()->setPhase(WorldStatus::SERVER_READY_PHASE);
     uint64_t start_time = event->data().getUInt64();
+    powerup_manager->setRandomSeed(start_time);
     joinStartGameThread();
     m_start_game_thread = std::thread([start_time, this]()
         {

src/network/protocols/server_lobby.cpp

@@ -20,6 +20,7 @@
 
 #include "config/user_config.hpp"
 #include "items/item_manager.hpp"
+#include "items/powerup_manager.hpp"
 #include "karts/abstract_kart.hpp"
 #include "karts/controller/player_controller.hpp"
 #include "karts/kart_properties_manager.hpp"
@@ -2369,6 +2370,7 @@ void ServerLobby::configPeersStartTime()
     // Start up time will be after 2500ms, so even if this packet is sent late
     // (due to packet loss), the start time will still ahead of current time
     uint64_t start_time = STKHost::get()->getNetworkTimer() + (uint64_t)2500;
+    powerup_manager->setRandomSeed(start_time);
     NetworkString* ns = getNetworkString(10);
     ns->addUInt8(LE_START_RACE).addUInt64(start_time);
     sendMessageToPeers(ns, /*reliable*/true);

src/tracks/track.cpp

@@ -53,6 +53,7 @@
 #include "items/item.hpp"
 #include "items/item_manager.hpp"
 #include "items/network_item_manager.hpp"
+#include "items/powerup_manager.hpp"
 #include "karts/abstract_kart.hpp"
 #include "karts/kart_properties.hpp"
 #include "modes/linear_world.hpp"
@@ -1855,8 +1856,10 @@ void Track::loadTrackModel(bool reverse_track, unsigned int mode_id)
     else
     {
         // Seed random engine locally
-        ItemManager::updateRandomSeed((uint32_t)StkTime::getTimeSinceEpoch());
+        uint32_t seed = (uint32_t)StkTime::getTimeSinceEpoch();
+        ItemManager::updateRandomSeed(seed);
         ItemManager::create();
+        powerup_manager->setRandomSeed(seed);
     }
 
     // Set the default start positions. Node that later the default