1 files changed, 181 insertions, 3 deletions

diff --git a/src/Entities/Pawn.cpp b/src/Entities/Pawn.cpp
index ca2d413df..6b404f7e0 100644
--- a/src/Entities/Pawn.cpp
+++ b/src/Entities/Pawn.cpp
@@ -2,17 +2,22 @@
 #include "Globals.h"  // NOTE: MSVC stupidness requires this to be the same across all modules
 
 #include "Pawn.h"
+#include "Player.h"
 #include "../World.h"
 #include "../Bindings/PluginManager.h"
 #include "BoundingBox.h"
+#include "../Blocks/BlockHandler.h"
+#include "EffectID.h"
 
 
 
 
 
 cPawn::cPawn(eEntityType a_EntityType, double a_Width, double a_Height) :
-	super(a_EntityType, 0, 0, 0, a_Width, a_Height)
-	, m_EntityEffects(tEffectMap())
+	super(a_EntityType, 0, 0, 0, a_Width, a_Height),
+	m_EntityEffects(tEffectMap()),
+	m_LastGroundHeight(0),
+	m_bTouchGround(false)
 {
 	SetGravity(-32.0f);
 	SetAirDrag(0.02f);
@@ -79,8 +84,10 @@ void cPawn::Tick(std::chrono::milliseconds a_Dt, cChunk & a_Chunk)
 	} Callback(this);
 
 	m_World->ForEachEntityInBox(cBoundingBox(GetPosition(), GetWidth(), GetHeight()), Callback);
-	
+
 	super::Tick(a_Dt, a_Chunk);
+
+	HandleFalling();
 }
 
 
@@ -185,3 +192,174 @@ void cPawn::ClearEntityEffects()
 
 
 
+
+
+void cPawn::HandleFalling(void)
+{
+	/* Not pretty looking, and is more suited to wherever server-sided collision detection is implemented.
+	The following condition sets on-ground-ness if
+	The player isn't swimming or flying (client hardcoded conditions) and
+	they're on a block (Y is exact) - ensure any they could be standing on (including on the edges) is solid or
+	they're on a slab (Y significand is 0.5) - ditto with slab check
+	they're on a snow layer (Y divisible by 0.125) - ditto with snow layer check
+	*/
+
+	static const auto HalfWidth = GetWidth() / 2;
+	static const auto EPS = 0.0001;
+
+	/* Since swimming is decided in a tick and is asynchronous to this, we have to check for dampeners ourselves.
+	The behaviour as of 1.8.9 is the following:
+	- Landing in water alleviates all fall damage
+	- Passing through any liquid (water + lava) and cobwebs "slows" the player down,
+	i.e. resets the fall distance to that block, but only after checking for fall damage
+	(this means that plummeting into lava will still kill the player via fall damage, although cobwebs
+	will slow players down enough to have multiple updates that keep them alive)
+	- Slime blocks reverse falling velocity, unless it's a crouching player, in which case they act as standard blocks.
+	They also reset the topmost point of the damage calculation with each bounce,
+	so if the block is removed while the player is bouncing or crouches after a bounce, the last bounce's zenith is considered as fall damage.
+
+	With this in mind, we first check the block at the player's feet, then the one below that (because fences),
+	and decide which behaviour we want to go with.
+	*/
+	BLOCKTYPE BlockAtFoot = (cChunkDef::IsValidHeight(POSY_TOINT)) ? GetWorld()->GetBlock(POS_TOINT) : E_BLOCK_AIR;
+
+	/* We initialize these with what the foot is really IN, because for sampling we will move down with the epsilon above */
+	bool IsFootInWater = IsBlockWater(BlockAtFoot);
+	bool IsFootInLiquid = IsFootInWater || IsBlockLava(BlockAtFoot) || (BlockAtFoot == E_BLOCK_COBWEB);  // okay so cobweb is not _technically_ a liquid...
+	bool IsFootOnSlimeBlock = false;
+
+	/* The "cross" we sample around to account for the player width/girth */
+	static const struct
+	{
+		int x, z;
+	} CrossSampleCoords[] =
+	{
+		{ 0, 0 },
+		{ 1, 0 },
+		{ -1, 0 },
+		{ 0, 1 },
+		{ 0, -1 },
+	};
+
+	/* The blocks we're interested in relative to the player to account for larger than 1 blocks.
+	This can be extended to do additional checks in case there are blocks that are represented as one block
+	in memory but have a hitbox larger than 1 (like fences) */
+	static const struct
+	{
+		int x, y, z;
+	} BlockSampleOffsets[] =
+	{
+		{ 0, 0, 0 },
+		{ 0, -1, 0 },
+	};
+
+	/* Here's the rough outline of how this mechanism works:
+	We take the player's pointlike position (sole of feet), and expand it into a crosslike shape.
+	If any of the five points hit a block, we consider the player to be "on" (or "in") the ground. */
+	bool OnGround = false;
+	for (size_t i = 0; i < ARRAYCOUNT(CrossSampleCoords); i++)
+	{
+		/* We calculate from the player's position, one of the cross-offsets above, and we move it down slightly so it's beyond inaccuracy.
+		The added advantage of this method is that if the player is simply standing on the floor,
+		the point will move into the next block, and the floor() will retrieve that instead of air. */
+		Vector3d CrossTestPosition = GetPosition() + Vector3d(CrossSampleCoords[i].x * HalfWidth, -EPS, CrossSampleCoords[i].z * HalfWidth);
+
+		/* We go through the blocks that we consider "relevant" */
+		for (size_t j = 0; j < ARRAYCOUNT(BlockSampleOffsets); j++)
+		{
+			Vector3i BlockTestPosition = CrossTestPosition.Floor() + Vector3i(BlockSampleOffsets[j].x, BlockSampleOffsets[j].y, BlockSampleOffsets[j].z);
+
+			if (!cChunkDef::IsValidHeight(BlockTestPosition.y))
+			{
+				continue;
+			}
+
+			BLOCKTYPE Block = GetWorld()->GetBlock(BlockTestPosition);
+			NIBBLETYPE BlockMeta = GetWorld()->GetBlockMeta(BlockTestPosition);
+
+			/* we do the cross-shaped sampling to check for water / liquids, but only on our level because water blocks are never bigger than unit voxels */
+			if (j == 0)
+			{
+				IsFootInWater |= IsBlockWater(Block);
+				IsFootInLiquid |= IsFootInWater || IsBlockLava(Block) || (Block == E_BLOCK_COBWEB);  // okay so cobweb is not _technically_ a liquid...
+				IsFootOnSlimeBlock |= (Block == E_BLOCK_SLIME_BLOCK);
+			}
+
+			/* If the block is solid, and the blockhandler confirms the block to be inside, we're officially on the ground. */
+			if ((cBlockInfo::IsSolid(Block)) && (cBlockInfo::GetHandler(Block)->IsInsideBlock(CrossTestPosition - BlockTestPosition, Block, BlockMeta)))
+			{
+				OnGround = true;
+			}
+		}
+	}
+
+	// Update the ground height to have the highest position of the player (i.e. jumping up adds to the eventual fall damage)
+	if (!OnGround)
+	{
+		m_LastGroundHeight = std::max(m_LastGroundHeight, GetPosY());
+	}
+
+	/* So here's the use of the rules above: */
+	/* 1. Falling in water absorbs all fall damage */
+	bool FallDamageAbsorbed = IsFootInWater;
+
+	/* 2. Falling in liquid (lava, water, cobweb) or hitting a slime block resets the "fall zenith".
+	Note: Even though the pawn bounces back with no damage after hitting the slime block,
+	the "fall zenith" will continue to increase back up when flying upwards - which is good */
+	bool FallDistanceReset = IsFootOnSlimeBlock || IsFootInLiquid;
+	bool IsFlying = false;
+	bool ShouldBounceOnSlime = true;
+
+	if (GetEntityType() == eEntityType::etPlayer)
+	{
+		cPlayer * Player = static_cast<cPlayer *>(this);
+		IsFlying = Player->IsFlying();
+
+		/* 3. If the player is flying or climbing, absorb fall damage */
+		FallDamageAbsorbed |= IsFlying || Player->IsClimbing();
+
+		/* 4. If the player is about to bounce on a slime block and is not crouching, absorb all fall damage  */
+		ShouldBounceOnSlime = !Player->IsCrouched();
+		FallDamageAbsorbed |= (IsFootOnSlimeBlock && ShouldBounceOnSlime);
+	}
+	else
+	{
+		/* 5. Bouncing on a slime block absorbs all fall damage  */
+		FallDamageAbsorbed |= IsFootOnSlimeBlock;
+	}
+
+	/* If the player is not crouching or is not a player, shoot them back up.
+	NOTE: this will only work in some cases; should be done in HandlePhysics() */
+	if (IsFootOnSlimeBlock && ShouldBounceOnSlime)
+	{
+		SetSpeedY(-GetSpeedY());
+	}
+
+	if (!IsFlying && OnGround)
+	{
+		auto Damage = static_cast<int>(m_LastGroundHeight - GetPosY() - 3.0);
+		if ((Damage > 0) && !FallDamageAbsorbed)
+		{
+			TakeDamage(dtFalling, nullptr, Damage, Damage, 0);
+
+			// Fall particles
+			int ParticleSize = static_cast<int>((std::min(15, Damage) - 1.f) * ((50.f - 20.f) / (15.f - 1.f)) + 20.f);
+			GetWorld()->BroadcastSoundParticleEffect(EffectID::PARTICLE_FALL_PARTICLES, POSX_TOINT, POSY_TOINT - 1, POSZ_TOINT, ParticleSize);
+		}
+
+		m_bTouchGround = true;
+		m_LastGroundHeight = GetPosY();
+	}
+	else
+	{
+		m_bTouchGround = false;
+	}
+
+	/* Note: it is currently possible to fall through lava and still die from fall damage
+	because of the client skipping an update about the lava block. This can only be resolved by
+	somehow integrating these above checks into the tracer in HandlePhysics. */
+	if (FallDistanceReset)
+	{
+		m_LastGroundHeight = GetPosY();
+	}
+}