Core/Movement: Knockback improvements (#28081)

* Knockbacks with negative speeds will now be validated and processed.
* Creatures that cast knockback spells on themselves will use their orientation to determine the direction of movement.

2 files changed, 18 insertions, 7 deletions

diff --git a/src/server/game/Movement/MotionMaster.cpp b/src/server/game/Movement/MotionMaster.cpp
index bccfa78dd0d..85bb2e365f3 100644
--- a/src/server/game/Movement/MotionMaster.cpp
+++ b/src/server/game/Movement/MotionMaster.cpp
@@ -806,23 +806,34 @@ 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));
+    _owner->MovePositionToFirstCollision(dest, dist, o);
 
     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.SetParabolic(max_height, 0);
         init.SetOrientationFixed(true);
-        init.SetVelocity(speedXY);
+        if (speedXY >= 0.01f)
+            init.SetVelocity(speedXY);
         if (effect)
             init.SetSpellEffectExtraData(*effect);
     };
diff --git a/src/server/game/Spells/SpellEffects.cpp b/src/server/game/Spells/SpellEffects.cpp
index 9954a89d928..95df657d03d 100644
--- a/src/server/game/Spells/SpellEffects.cpp
+++ b/src/server/game/Spells/SpellEffects.cpp
@@ -4040,9 +4040,9 @@ void Spell::EffectKnockBack()
         return;
 
     float ratio = 0.1f;
-    float speedxy = float(effectInfo->MiscValue) * ratio;
-    float speedz = float(damage) * ratio;
-    if (speedxy < 0.01f && speedz < 0.01f)
+    float speedXY = float(effectInfo->MiscValue) * ratio;
+    float speedZ = float(damage) * ratio;
+    if (std::abs(speedXY) < 0.01f && std::abs(speedZ) < 0.01f)
         return;
 
     Position origin;
@@ -4056,7 +4056,7 @@ void Spell::EffectKnockBack()
     else //if (effectInfo->Effect == SPELL_EFFECT_KNOCK_BACK)
         origin = m_caster->GetPosition();
 
-    unitTarget->KnockbackFrom(origin, speedxy, speedz);
+    unitTarget->KnockbackFrom(origin, speedXY, speedZ);
 
     Unit::ProcSkillsAndAuras(GetUnitCasterForEffectHandlers(), unitTarget, PROC_FLAG_NONE, { PROC_FLAG_NONE, PROC_FLAG_2_KNOCKBACK },
         PROC_SPELL_TYPE_MASK_ALL, PROC_SPELL_PHASE_HIT, PROC_HIT_NONE, nullptr, nullptr, nullptr);