From bd6716d89d869478f3e4f8b1444463fa1cf7743e Mon Sep 17 00:00:00 2001
From: Alexei Kotov <alexdobrohotov@yandex.ru>
Date: Sun, 19 Jun 2022 22:21:41 +0300
Subject: [PATCH] Give AITravel time to end if the actor is close to the
 destination

---
 apps/openmw/mwmechanics/aitravel.cpp | 62 +++++++++++++---------------
 apps/openmw/mwmechanics/aitravel.hpp |  2 +-
 2 files changed, 29 insertions(+), 35 deletions(-)

diff --git a/apps/openmw/mwmechanics/aitravel.cpp b/apps/openmw/mwmechanics/aitravel.cpp
index 5d453c4b44..378099e7d1 100644
--- a/apps/openmw/mwmechanics/aitravel.cpp
+++ b/apps/openmw/mwmechanics/aitravel.cpp
@@ -17,6 +17,8 @@
 namespace
 {
 
+    constexpr float TRAVEL_FINISH_TIME = 2.f;
+
 bool isWithinMaxRange(const osg::Vec3f& pos1, const osg::Vec3f& pos2)
 {
     // Maximum travel distance for vanilla compatibility.
@@ -25,24 +27,17 @@ bool isWithinMaxRange(const osg::Vec3f& pos1, const osg::Vec3f& pos2)
     return (pos1 - pos2).length2() <= 7168*7168;
 }
 
-    float getActorRadius(const MWWorld::ConstPtr& actor)
-    {
-        const osg::Vec3f halfExtents = MWBase::Environment::get().getWorld()->getPathfindingHalfExtents(actor);
-        return std::max(halfExtents.x(), std::max(halfExtents.y(), halfExtents.z()));
-    }
 }
 
 namespace MWMechanics
 {
     AiTravel::AiTravel(float x, float y, float z, bool repeat, AiTravel*)
-        : TypedAiPackage<AiTravel>(repeat), mX(x), mY(y), mZ(z), mHidden(false)
-        , mDestinationCheck(MWBase::Environment::get().getWorld()->getPrng())
+        : TypedAiPackage<AiTravel>(repeat), mX(x), mY(y), mZ(z), mHidden(false), mDestinationTimer(TRAVEL_FINISH_TIME)
     {
     }
 
     AiTravel::AiTravel(float x, float y, float z, AiInternalTravel* derived)
-        : TypedAiPackage<AiTravel>(derived), mX(x), mY(y), mZ(z), mHidden(true)
-        , mDestinationCheck(MWBase::Environment::get().getWorld()->getPrng())
+        : TypedAiPackage<AiTravel>(derived), mX(x), mY(y), mZ(z), mHidden(true), mDestinationTimer(TRAVEL_FINISH_TIME)
     {
     }
 
@@ -53,7 +48,7 @@ namespace MWMechanics
 
     AiTravel::AiTravel(const ESM::AiSequence::AiTravel *travel)
         : TypedAiPackage<AiTravel>(travel->mRepeat), mX(travel->mData.mX), mY(travel->mData.mY), mZ(travel->mData.mZ), mHidden(false)
-        , mDestinationCheck(MWBase::Environment::get().getWorld()->getPrng())
+        , mDestinationTimer(TRAVEL_FINISH_TIME)
     {
         // Hidden ESM::AiSequence::AiTravel package should be converted into MWMechanics::AiInternalTravel type
         assert(!travel->mHidden);
@@ -78,35 +73,34 @@ namespace MWMechanics
         if (!isWithinMaxRange(targetPos, actorPos))
             return mHidden;
 
-        // Unfortunately, with vanilla assets destination is sometimes blocked by other actor.
-        // If we got close to target, check for actors nearby. If they are, finish AI package.
-        if (mDestinationCheck.update(duration) == Misc::TimerStatus::Elapsed)
-        {
-            std::vector<MWWorld::Ptr> occupyingActors;
-            if (isAreaOccupiedByOtherActor(actor, targetPos, true, &occupyingActors))
-            {
-                const float actorRadius = getActorRadius(actor);
-                const float distanceToTarget = distance(actorPos, targetPos);
-                for (const MWWorld::Ptr& other : occupyingActors)
-                {
-                    const float otherRadius = getActorRadius(other);
-                    const auto [minRadius, maxRadius] = std::minmax(actorRadius, otherRadius);
-                    constexpr float toleranceFactor = 1.25;
-                    if (minRadius * toleranceFactor + maxRadius > distanceToTarget)
-                    {
-                        actor.getClass().getMovementSettings(actor).mPosition[1] = 0;
-                        return true;
-                    }
-                }
-            }
-        }
-
         if (pathTo(actor, targetPos, duration))
         {
             actor.getClass().getMovementSettings(actor).mPosition[1] = 0;
             return true;
         }
-        return false;
+
+        // If we've been close enough to the destination for some time give up like Morrowind.
+        // The end condition should be pretty much accurate.
+        // FIXME: But the timing isn't. Right now we're being very generous,
+        // but Morrowind might stop the actor prematurely under unclear conditions.
+
+        // Note Morrowind uses the halved eye level, but this is close enough.
+        float dist = distanceIgnoreZ(actorPos, targetPos) - MWBase::Environment::get().getWorld()->getHalfExtents(actor).z();
+        const float endTolerance = std::max(64.f, actor.getClass().getCurrentSpeed(actor) * duration);
+
+        // Even if we have entered the threshold, we might have been pushed away. Reset the timer if we're currently too far.
+        if (dist > endTolerance)
+        {
+            mDestinationTimer = TRAVEL_FINISH_TIME;
+            return false;
+        }
+
+        mDestinationTimer -= duration;
+        if (mDestinationTimer > 0)
+            return false;
+
+        actor.getClass().getMovementSettings(actor).mPosition[1] = 0;
+        return true;
     }
 
     void AiTravel::fastForward(const MWWorld::Ptr& actor, AiState& state)
diff --git a/apps/openmw/mwmechanics/aitravel.hpp b/apps/openmw/mwmechanics/aitravel.hpp
index 303df7b105..60a68d9cc5 100644
--- a/apps/openmw/mwmechanics/aitravel.hpp
+++ b/apps/openmw/mwmechanics/aitravel.hpp
@@ -53,7 +53,7 @@ namespace MWMechanics
 
             const bool mHidden;
 
-            AiReactionTimer mDestinationCheck;
+            float mDestinationTimer;
     };
 
     struct AiInternalTravel final : public AiTravel