From 5a4872393a77c0dc35f1f633a15143bf13e87dba Mon Sep 17 00:00:00 2001
From: fredzio <chardon.frederic@gmail.com>
Date: Thu, 3 Dec 2020 12:57:57 +0100
Subject: [PATCH] Rework actor position reset. While solving the issue with
 invalid position being used under heavy load, I introduced a regression that
 prevented the position to be updated in case of teleport. Move the logic in
 its own function and decide in PhysicsSystem whether a reset is needed.

---
 apps/openmw/mwphysics/mtphysics.cpp     | 25 ++++++++++---------------
 apps/openmw/mwphysics/mtphysics.hpp     |  4 +++-
 apps/openmw/mwphysics/physicssystem.cpp | 12 +++++++++++-
 3 files changed, 24 insertions(+), 17 deletions(-)

diff --git a/apps/openmw/mwphysics/mtphysics.cpp b/apps/openmw/mwphysics/mtphysics.cpp
index 2d4009e7d8..bdffcef44f 100644
--- a/apps/openmw/mwphysics/mtphysics.cpp
+++ b/apps/openmw/mwphysics/mtphysics.cpp
@@ -212,7 +212,7 @@ namespace MWPhysics
             thread.join();
     }
 
-    const PtrPositionList& PhysicsTaskScheduler::moveActors(int numSteps, float timeAccum, std::vector<ActorFrameData>&& actorsData, bool skipSimulation, osg::Timer_t frameStart, unsigned int frameNumber, osg::Stats& stats)
+    const PtrPositionList& PhysicsTaskScheduler::moveActors(int numSteps, float timeAccum, std::vector<ActorFrameData>&& actorsData, osg::Timer_t frameStart, unsigned int frameNumber, osg::Stats& stats)
     {
         // This function run in the main thread.
         // While the mSimulationMutex is held, background physics threads can't run.
@@ -263,20 +263,6 @@ namespace MWPhysics
         if (mAdvanceSimulation)
             mWorldFrameData = std::make_unique<WorldFrameData>();
 
-        // we are asked to skip the simulation (load a savegame for instance)
-        // just return the actors' reference position without applying the movements
-        if (skipSimulation)
-        {
-            mMovementResults.clear();
-            for (const auto& m : mActorsFrameData)
-            {
-                m.mActorRaw->setStandingOnPtr(nullptr);
-                m.mActorRaw->resetPosition();
-                mMovementResults[m.mPtr] = m.mActorRaw->getWorldPosition();
-            }
-            return mMovementResults;
-        }
-
         if (mNumThreads == 0)
         {
             mMovementResults.clear();
@@ -311,6 +297,15 @@ namespace MWPhysics
         return mPreviousMovementResults;
     }
 
+    const PtrPositionList& PhysicsTaskScheduler::resetSimulation()
+    {
+        std::unique_lock lock(mSimulationMutex);
+        mMovementResults.clear();
+        mPreviousMovementResults.clear();
+        mActorsFrameData.clear();
+        return mMovementResults;
+    }
+
     void PhysicsTaskScheduler::rayTest(const btVector3& rayFromWorld, const btVector3& rayToWorld, btCollisionWorld::RayResultCallback& resultCallback) const
     {
         MaybeSharedLock lock(mCollisionWorldMutex, mThreadSafeBullet);
diff --git a/apps/openmw/mwphysics/mtphysics.hpp b/apps/openmw/mwphysics/mtphysics.hpp
index c061fe01da..f7a131ca26 100644
--- a/apps/openmw/mwphysics/mtphysics.hpp
+++ b/apps/openmw/mwphysics/mtphysics.hpp
@@ -32,7 +32,9 @@ namespace MWPhysics
             /// @param timeAccum accumulated time from previous run to interpolate movements
             /// @param actorsData per actor data needed to compute new positions
             /// @return new position of each actor
-            const PtrPositionList& moveActors(int numSteps, float timeAccum, std::vector<ActorFrameData>&& actorsData, bool skip, osg::Timer_t frameStart, unsigned int frameNumber, osg::Stats& stats);
+            const PtrPositionList& moveActors(int numSteps, float timeAccum, std::vector<ActorFrameData>&& actorsData, osg::Timer_t frameStart, unsigned int frameNumber, osg::Stats& stats);
+
+            const PtrPositionList& resetSimulation();
 
             // Thread safe wrappers
             void rayTest(const btVector3& rayFromWorld, const btVector3& rayToWorld, btCollisionWorld::RayResultCallback& resultCallback) const;
diff --git a/apps/openmw/mwphysics/physicssystem.cpp b/apps/openmw/mwphysics/physicssystem.cpp
index 7aa1f59141..cdbad2cddd 100644
--- a/apps/openmw/mwphysics/physicssystem.cpp
+++ b/apps/openmw/mwphysics/physicssystem.cpp
@@ -676,7 +676,17 @@ namespace MWPhysics
 
         mTimeAccum -= numSteps * mPhysicsDt;
 
-        return mTaskScheduler->moveActors(numSteps, mTimeAccum, prepareFrameData(numSteps), skipSimulation, frameStart, frameNumber, stats);
+        if (skipSimulation)
+        {
+            for (auto& [_, actor] : mActors)
+            {
+                actor->resetPosition();
+                actor->setStandingOnPtr(nullptr);
+            }
+            return mTaskScheduler->resetSimulation();
+        }
+
+        return mTaskScheduler->moveActors(numSteps, mTimeAccum, prepareFrameData(numSteps), frameStart, frameNumber, stats);
     }
 
     std::vector<ActorFrameData> PhysicsSystem::prepareFrameData(int numSteps)