From 01e72ddb6567531b16f92af2564b853878b6ef65 Mon Sep 17 00:00:00 2001
From: changyong guo <guo1487@163.com>
Date: Mon, 23 Jul 2018 17:24:00 +0800
Subject: Rewrite explosion knock back (#4251)

1. Base knockback on an entity's bounding box intersection with the explosion
2. Armor blast protection reduces knockback
3. Don't apply knockback to players flying in creative mode

Fixes #4139
---
 src/Entities/Entity.cpp | 64 ++++++++++++++++++++++++++++++++++++++++++++++++-
 src/Entities/Entity.h   | 11 ++++++++-
 src/Entities/Player.cpp | 28 ++++++++++++++++++++++
 src/Entities/Player.h   |  2 ++
 4 files changed, 103 insertions(+), 2 deletions(-)

(limited to 'src/Entities')

diff --git a/src/Entities/Entity.cpp b/src/Entities/Entity.cpp
index d1fdcfd39..4ecc5c4da 100644
--- a/src/Entities/Entity.cpp
+++ b/src/Entities/Entity.cpp
@@ -14,7 +14,7 @@
 #include "Items/ItemHandler.h"
 #include "../FastRandom.h"
 #include "../NetherPortalScanner.h"
-
+#include "../BoundingBox.h"
 
 
 
@@ -690,6 +690,33 @@ int cEntity::GetEnchantmentCoverAgainst(const cEntity * a_Attacker, eDamageType
 
 
 
+
+float cEntity::GetEnchantmentBlastKnockbackReduction()
+{
+	UInt32 MaxLevel = 0;
+
+	const cItem ArmorItems[] = { GetEquippedHelmet(), GetEquippedChestplate(), GetEquippedLeggings(), GetEquippedBoots() };
+
+	for (auto & Item : ArmorItems)
+	{
+		UInt32 Level = Item.m_Enchantments.GetLevel(cEnchantments::enchBlastProtection);
+		if (Level > MaxLevel)
+		{
+			// Get max blast protection
+			MaxLevel = Level;
+		}
+	}
+
+	// Max blast protect level is 4, each level provide 15% knock back reduction
+	MaxLevel = std::min<UInt32>(MaxLevel, 4);
+	return MaxLevel * 0.15f;
+}
+
+
+
+
+
+
 int cEntity::GetArmorCoverAgainst(const cEntity * a_Attacker, eDamageType a_DamageType, int a_Damage)
 {
 	// Returns the hitpoints out of a_RawDamage that the currently equipped armor would cover
@@ -2241,3 +2268,38 @@ void cEntity::RemoveLeashedMob(cMonster * a_Monster)
 
 	m_LeashedMobs.remove(a_Monster);
 }
+
+
+
+
+
+
+float cEntity::GetExplosionExposureRate(Vector3d a_ExplosionPosition, float a_ExlosionPower)
+{
+	double EntitySize = m_Width * m_Width * m_Height;
+	if (EntitySize <= 0)
+	{
+		// Handle entity with invalid size
+		return 0;
+	}
+
+	cBoundingBox EntityBox(GetPosition(), m_Width / 2, m_Height);
+	cBoundingBox ExplosionBox(a_ExplosionPosition, a_ExlosionPower * 2.0);
+	cBoundingBox IntersectionBox(EntityBox);
+
+	bool Overlap = EntityBox.Intersect(ExplosionBox, IntersectionBox);
+	if (Overlap)
+	{
+		Vector3d Diff = IntersectionBox.GetMax() - IntersectionBox.GetMin();
+		double OverlapSize = Diff.x * Diff.y * Diff.z;
+
+		return static_cast<float>(OverlapSize / EntitySize);
+	}
+	else
+	{
+		return 0;
+	}
+}
+
+
+
diff --git a/src/Entities/Entity.h b/src/Entities/Entity.h
index 7ac12c95b..ae150b4e2 100644
--- a/src/Entities/Entity.h
+++ b/src/Entities/Entity.h
@@ -333,6 +333,10 @@ public:
 	/** Returns the hitpoints that the currently equipped armor's enchantments would cover */
 	virtual int GetEnchantmentCoverAgainst(const cEntity * a_Attacker, eDamageType a_DamageType, int a_Damage);
 
+	/** Returns explosion knock back reduction percent from blast protection level
+	@return knock back reduce percent */
+	virtual float GetEnchantmentBlastKnockbackReduction();
+
 	/** Returns the knockback amount that the currently equipped items would cause to a_Receiver on a hit */
 	virtual double GetKnockbackAmountAgainst(const cEntity & a_Receiver);
 
@@ -545,6 +549,12 @@ public:
 	/** Returs whether the entity has any mob leashed to */
 	bool HasAnyMobLeashed() const { return m_LeashedMobs.size() > 0; }
 
+	/** a lightweight calculation approach to get explosion exposure rate
+	@param a_ExplosionPosition explosion position
+	@param a_ExlosionPower explosion power
+	@return exposure rate */
+	virtual float GetExplosionExposureRate(Vector3d a_ExplosionPosition, float a_ExlosionPower);
+
 protected:
 	/** Structure storing the portal delay timer and cooldown boolean */
 	struct sPortalCooldownData
@@ -714,5 +724,4 @@ private:
 
 	/** List of leashed mobs to this entity */
 	cMonsterList m_LeashedMobs;
-
 } ;  // tolua_export
diff --git a/src/Entities/Player.cpp b/src/Entities/Player.cpp
index d8bb22e2f..181a54870 100644
--- a/src/Entities/Player.cpp
+++ b/src/Entities/Player.cpp
@@ -3069,3 +3069,31 @@ float cPlayer::GetPlayerRelativeBlockHardness(BLOCKTYPE a_Block)
 	// LOGD("blockHardness: %f, digSpeed: %f, canHarvestBlockDivisor: %f\n", blockHardness, digSpeed, canHarvestBlockDivisor);
 	return (blockHardness < 0) ? 0 : ((digSpeed / blockHardness) / canHarvestBlockDivisor);
 }
+
+
+
+
+
+
+float cPlayer::GetExplosionExposureRate(Vector3d a_ExplosionPosition, float a_ExlosionPower)
+{
+	if (
+		IsGameModeSpectator() ||
+		(IsGameModeCreative() && !IsOnGround())
+	)
+	{
+		return 0;  // No impact from explosion
+	}
+
+	return super::GetExplosionExposureRate(a_ExplosionPosition, a_ExlosionPower);
+}
+
+
+
+
+
+
+
+
+
+
diff --git a/src/Entities/Player.h b/src/Entities/Player.h
index e710e8396..c9249b2f1 100644
--- a/src/Entities/Player.h
+++ b/src/Entities/Player.h
@@ -759,6 +759,8 @@ protected:
 	This can be used both for online and offline UUIDs. */
 	AString GetUUIDFileName(const cUUID & a_UUID);
 
+	/** get player explosion exposure rate */
+	virtual float GetExplosionExposureRate(Vector3d a_ExplosionPosition, float a_ExlosionPower) override;
 private:
 
 	/** Pins the player to a_Location until Unfreeze() is called.
-- 
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