2 files changed, 50 insertions, 11 deletions

diff --git a/src/server/game/Movement/MotionMaster.cpp b/src/server/game/Movement/MotionMaster.cpp
index bccfa78dd0d..fb55617f58a 100644
--- a/src/server/game/Movement/MotionMaster.cpp
+++ b/src/server/game/Movement/MotionMaster.cpp
@@ -29,6 +29,7 @@
 #include "PathGenerator.h"
 #include "Player.h"
 #include "ScriptSystem.h"
+#include <boost/container/static_vector.hpp>
 #include <algorithm>
 #include <iterator>
 
@@ -806,20 +807,44 @@ void MotionMaster::MoveKnockbackFrom(Position const& origin, float speedXY, floa
     if (_owner->GetTypeId() == TYPEID_PLAYER)
         return;
 
-    if (speedXY < 0.01f)
+    if (std::abs(speedXY) < 0.01f && std::abs(speedZ) < 0.01f)
         return;
 
     Position dest = _owner->GetPosition();
+    float o = dest == origin ? 0.0f : _owner->GetRelativeAngle(origin) + float(M_PI);
+    if (speedXY < 0)
+    {
+        speedXY = -speedXY;
+        o = o - float(M_PI);
+    }
+
+    if (speedZ < 0)
+        speedZ = -speedZ; // doesn't seem to be supported on official servers - packet sent for knockback with positive and negative speed has the same flags and JumpGravity
+
     float moveTimeHalf = speedZ / Movement::gravity;
     float dist = 2 * moveTimeHalf * speedXY;
     float max_height = -Movement::computeFallElevation(moveTimeHalf, false, -speedZ);
 
-    // Use a mmap raycast to get a valid destination.
-    _owner->MovePositionToFirstCollision(dest, dist, _owner->GetRelativeAngle(origin) + float(M_PI));
+    boost::container::static_vector<G3D::Vector3, 3> path;
+    path.push_back(PositionToVector3(dest));
+
+    if (dist > 0.01f)
+    {
+        // Use a mmap raycast to get a valid destination.
+        _owner->MovePositionToFirstCollision(dest, dist, o);
+        path.push_back(PositionToVector3(dest));
+    }
+    else
+    {
+        // vertical knockbacks get a fake 0.5 higher additional point to avoid clientside spline length checks
+        // sniffs confirmed that it is always 0.5, no matter what the max height is
+        path.push_back(PositionToVector3(dest.GetPositionWithOffset({ 0.0f, 0.0f, 0.5f })));
+        path.push_back(PositionToVector3(dest));
+    }
 
     std::function<void(Movement::MoveSplineInit&)> initializer = [=, effect = (spellEffectExtraData ? Optional<Movement::SpellEffectExtraData>(*spellEffectExtraData) : Optional<Movement::SpellEffectExtraData>())](Movement::MoveSplineInit& init)
     {
-        init.MoveTo(dest.GetPositionX(), dest.GetPositionY(), dest.GetPositionZ(), false);
+        init.MovebyPath({ path.data(), path.size() });
         init.SetParabolic(max_height, 0);
         init.SetOrientationFixed(true);
         init.SetVelocity(speedXY);
diff --git a/src/server/game/Movement/Spline/MoveSpline.cpp b/src/server/game/Movement/Spline/MoveSpline.cpp
index a317b018ed6..7d76570b81d 100644
--- a/src/server/game/Movement/Spline/MoveSpline.cpp
+++ b/src/server/game/Movement/Spline/MoveSpline.cpp
@@ -120,9 +120,8 @@ void MoveSpline::computeFallElevation(int32 time_point, float& el) const
 
 struct FallInitializer
 {
-    FallInitializer(float _start_elevation) : start_elevation(_start_elevation) { }
     float start_elevation;
-    inline int32 operator()(Spline<int32>& s, int32 i)
+    inline int32 operator()(Spline<int32> const& s, int32 i) const
     {
         return Movement::computeFallTime(start_elevation - s.getPoint(i+1).z, false) * 1000.f;
     }
@@ -132,11 +131,21 @@ enum{
     minimal_duration = 1
 };
 
+struct ParabolicInPlaceInitializer
+{
+    float parabolic_amplitude;
+    inline int32 operator()(Spline<int32> const& /*s*/, int32 /*i*/)
+    {
+        return time += Movement::computeFallTime(parabolic_amplitude, false) * 1000.f;
+    }
+
+    int32 time = minimal_duration;
+};
+
 struct CommonInitializer
 {
-    CommonInitializer(float _velocity) : velocityInv(1000.f/_velocity), time(minimal_duration) { }
     float velocityInv;
-    int32 time;
+    int32 time = minimal_duration;
     inline int32 operator()(Spline<int32>& s, int32 i)
     {
         time += (s.SegLength(i) * velocityInv);
@@ -160,12 +169,17 @@ void MoveSpline::init_spline(MoveSplineInitArgs const& args)
     // init spline timestamps
     if (splineflags.Falling)
     {
-        FallInitializer init(spline.getPoint(spline.first()).z);
+        FallInitializer init{ .start_elevation = spline.getPoint(spline.first()).z };
+        spline.initLengths(init);
+    }
+    else if (splineflags.Parabolic && args.velocity < 0.01f)
+    {
+        ParabolicInPlaceInitializer init{ .parabolic_amplitude = args.parabolic_amplitude };
         spline.initLengths(init);
     }
     else
     {
-        CommonInitializer init(args.velocity);
+        CommonInitializer init{ .velocityInv = 1000.0f / args.velocity };
         spline.initLengths(init);
     }
 
@@ -254,7 +268,7 @@ bool MoveSplineInitArgs::Validate(Unit const* unit)
     }()
 
     CHECK(path.size() > 1, unit->GetDebugInfo());
-    CHECK(velocity >= 0.01f, unit->GetDebugInfo());
+    CHECK(velocity >= 0.01f || (flags.Parabolic && parabolic_amplitude != 0.0f), unit->GetDebugInfo());
     CHECK(effect_start_point < std::ssize(path), unit->GetDebugInfo());
     CHECK(_checkPathLengths(), unit->GetGUID().ToString());
     if (spellEffectExtra)