From 03b86c232be6788443f687cd58acf98794e43db1 Mon Sep 17 00:00:00 2001
From: fredzio <chardon.frederic@gmail.com>
Date: Sat, 13 Mar 2021 09:52:05 +0100
Subject: [PATCH] Apply the position offset even if the simulation is not
 performed because we're too fast.

---
 apps/openmw/mwphysics/actor.cpp         | 11 +++++++++++
 apps/openmw/mwphysics/actor.hpp         |  7 +++++++
 apps/openmw/mwphysics/mtphysics.cpp     |  1 +
 apps/openmw/mwphysics/physicssystem.cpp |  4 ++++
 4 files changed, 23 insertions(+)

diff --git a/apps/openmw/mwphysics/actor.cpp b/apps/openmw/mwphysics/actor.cpp
index bbec4d445..06abe7240 100644
--- a/apps/openmw/mwphysics/actor.cpp
+++ b/apps/openmw/mwphysics/actor.cpp
@@ -190,6 +190,17 @@ void Actor::adjustPosition(const osg::Vec3f& offset)
     mPositionOffset += offset;
 }
 
+void Actor::applyOffsetChange()
+{
+    if (mPositionOffset.length() == 0)
+        return;
+    mWorldPosition += mPositionOffset;
+    mPosition += mPositionOffset;
+    mPreviousPosition += mPositionOffset;
+    mPositionOffset = osg::Vec3f();
+    mWorldPositionChanged = true;
+}
+
 osg::Vec3f Actor::getPosition() const
 {
     return mPosition;
diff --git a/apps/openmw/mwphysics/actor.hpp b/apps/openmw/mwphysics/actor.hpp
index 9d129f2ba..031125f40 100644
--- a/apps/openmw/mwphysics/actor.hpp
+++ b/apps/openmw/mwphysics/actor.hpp
@@ -96,9 +96,16 @@ namespace MWPhysics
           * Returns true if the new position is different.
           */
         bool setPosition(const osg::Vec3f& position);
+
+        // force set actor position to be as in Ptr::RefData
         void updatePosition();
+
+        // register a position offset that will be applied during simulation.
         void adjustPosition(const osg::Vec3f& offset);
 
+        // apply position offset. Can't be called during simulation
+        void applyOffsetChange();
+
         osg::Vec3f getPosition() const;
 
         osg::Vec3f getPreviousPosition() const;
diff --git a/apps/openmw/mwphysics/mtphysics.cpp b/apps/openmw/mwphysics/mtphysics.cpp
index 754bb60af..2b0db5b82 100644
--- a/apps/openmw/mwphysics/mtphysics.cpp
+++ b/apps/openmw/mwphysics/mtphysics.cpp
@@ -492,6 +492,7 @@ namespace MWPhysics
                 if (actor->setPosition(actorData.mPosition))
                 {
                     std::scoped_lock lock(mCollisionWorldMutex);
+                    actorData.mPosition = actor->getPosition(); // account for potential position change made by script
                     actor->updateCollisionObjectPosition();
                     mCollisionWorld->updateSingleAabb(actor->getCollisionObject());
                 }
diff --git a/apps/openmw/mwphysics/physicssystem.cpp b/apps/openmw/mwphysics/physicssystem.cpp
index b2decde2f..dc9ab629a 100644
--- a/apps/openmw/mwphysics/physicssystem.cpp
+++ b/apps/openmw/mwphysics/physicssystem.cpp
@@ -961,6 +961,10 @@ namespace MWPhysics
     void ActorFrameData::updatePosition()
     {
         mActorRaw->updateWorldPosition();
+        // If physics runs "fast enough", position are interpolated without simulation
+        // By calling this here, we are sure that offsets are applied at least once per frame,
+        // regardless of simulation speed.
+        mActorRaw->applyOffsetChange();
         mPosition = mActorRaw->getPosition();
         if (mMoveToWaterSurface)
         {