From 5402b214b31af60bc96cd4e47e9211715c3e99f5 Mon Sep 17 00:00:00 2001
From: Lane Kolbly <lane@rscheme.org>
Date: Fri, 28 Jul 2017 11:59:21 -0500
Subject: Check for intersection between placed blocks and entities. (#3850)

* Check for intersection between placed blocks and entities.

+ Implemented GetPlacementCollisionBox, to permit custom placement collision boxes for blocks.

* Factored block-entity placement checking into another function in cPlayer.

- Removed vector min/max functions

* Use GetWorld to get the world in DoesPlacingBlocksIntersectEntity.

+ Added block height checks, allow different cEntity subclasses to decide whether they will prevent block placement.
---
 src/Entities/Entity.h   |  3 ++
 src/Entities/Pickup.h   |  2 ++
 src/Entities/Player.cpp | 95 +++++++++++++++++++++++++++++++++++++++++++++++++
 src/Entities/Player.h   |  3 ++
 4 files changed, 103 insertions(+)

(limited to 'src/Entities')

diff --git a/src/Entities/Entity.h b/src/Entities/Entity.h
index d55955b0c..fb3103abc 100644
--- a/src/Entities/Entity.h
+++ b/src/Entities/Entity.h
@@ -191,6 +191,9 @@ public:
 	/** Returns the topmost class's parent class name for the object. cEntity returns an empty string (no parent). */
 	virtual const char * GetParentClass(void) const;
 
+	/** Returns whether blocks can be placed intersecting this entities' hitbox */
+	virtual bool DoesPreventBlockPlacement(void) const { return true; }
+
 	cWorld * GetWorld(void) const { return m_World; }
 
 	double           GetHeadYaw   (void) const { return m_HeadYaw; }  // In degrees
diff --git a/src/Entities/Pickup.h b/src/Entities/Pickup.h
index c2fcbd7f2..61e433e07 100644
--- a/src/Entities/Pickup.h
+++ b/src/Entities/Pickup.h
@@ -36,6 +36,8 @@ public:
 
 	virtual void Tick(std::chrono::milliseconds a_Dt, cChunk & a_Chunk) override;
 
+	virtual bool DoesPreventBlockPlacement(void) const override { return false; }
+
 	/** Returns whether this pickup is allowed to combine with other similar pickups */
 	bool CanCombine(void) const { return m_bCanCombine; }  // tolua_export
 
diff --git a/src/Entities/Player.cpp b/src/Entities/Player.cpp
index afeb8fa04..f66f2b73d 100644
--- a/src/Entities/Player.cpp
+++ b/src/Entities/Player.cpp
@@ -2641,8 +2641,103 @@ void cPlayer::SendBlocksAround(int a_BlockX, int a_BlockY, int a_BlockZ, int a_R
 
 
 
+bool cPlayer::DoesPlacingBlocksIntersectEntity(const sSetBlockVector & a_Blocks)
+{
+	// Compute the bounding box for each block to be placed
+	std::vector<cBoundingBox> PlacementBoxes;
+	cBoundingBox PlacingBounds(0, 0, 0, 0, 0, 0);
+	bool HasInitializedBounds = false;
+	for (auto blk: a_Blocks)
+	{
+		cBlockHandler * BlockHandler = cBlockInfo::GetHandler(blk.m_BlockType);
+		int x = blk.GetX();
+		int y = blk.GetY();
+		int z = blk.GetZ();
+		cBoundingBox BlockBox = BlockHandler->GetPlacementCollisionBox(
+			m_World->GetBlock(x - 1, y, z),
+			m_World->GetBlock(x + 1, y, z),
+			(y == 0) ? E_BLOCK_AIR : m_World->GetBlock(x, y - 1, z),
+			(y == cChunkDef::Height - 1) ? E_BLOCK_AIR : m_World->GetBlock(x, y + 1, z),
+			m_World->GetBlock(x, y, z - 1),
+			m_World->GetBlock(x, y, z + 1)
+		);
+		BlockBox.Move(x, y, z);
+
+		PlacementBoxes.push_back(BlockBox);
+
+		if (HasInitializedBounds)
+		{
+			PlacingBounds = PlacingBounds.Union(BlockBox);
+		}
+		else
+		{
+			PlacingBounds = BlockBox;
+			HasInitializedBounds = true;
+		}
+	}
+
+	cWorld * World = GetWorld();
+
+	// Check to see if any entity intersects any block being placed
+	class DoesIntersectBlock : public cEntityCallback
+	{
+	public:
+		const std::vector<cBoundingBox> & m_BoundingBoxes;
+
+		// The distance inside the block the entity can still be.
+		const double EPSILON = 0.0005;
+
+		DoesIntersectBlock(const std::vector<cBoundingBox> & a_BoundingBoxes) :
+			m_BoundingBoxes(a_BoundingBoxes)
+		{
+		}
+
+		virtual bool Item(cEntity * a_Entity) override
+		{
+			if (!a_Entity->DoesPreventBlockPlacement())
+			{
+				return false;
+			}
+			cBoundingBox EntBox(a_Entity->GetPosition(), a_Entity->GetWidth() / 2, a_Entity->GetHeight());
+			for (auto BlockBox: m_BoundingBoxes)
+			{
+
+				// Put in a little bit of wiggle room
+				BlockBox.Expand(-EPSILON, -EPSILON, -EPSILON);
+				if (EntBox.DoesIntersect(BlockBox))
+				{
+					return true;
+				}
+			}
+			return false;
+		}
+	} Callback(PlacementBoxes);
+
+	// See if any entities in that bounding box collide with anyone
+	if (!World->ForEachEntityInBox(PlacingBounds, Callback))
+	{
+		return true;
+	}
+
+	return false;
+}
+
+
+
+
+
 bool cPlayer::PlaceBlocks(const sSetBlockVector & a_Blocks)
 {
+	if (DoesPlacingBlocksIntersectEntity(a_Blocks))
+	{
+		// Abort - re-send all the current blocks in the a_Blocks' coords to the client:
+		for (auto blk2: a_Blocks)
+		{
+			m_World->SendBlockTo(blk2.GetX(), blk2.GetY(), blk2.GetZ(), this);
+		}
+		return false;
+	}
+
 	// Call the "placing" hooks; if any fail, abort:
 	cPluginManager * pm = cPluginManager::Get();
 	for (auto blk: a_Blocks)
diff --git a/src/Entities/Player.h b/src/Entities/Player.h
index 8ad803998..c00dbc7f1 100644
--- a/src/Entities/Player.h
+++ b/src/Entities/Player.h
@@ -485,6 +485,9 @@ public:
 	/** Update movement-related statistics. */
 	void UpdateMovementStats(const Vector3d & a_DeltaPos, bool a_PreviousIsOnGround);
 
+	/** Whether placing the given blocks would intersect any entitiy */
+	bool DoesPlacingBlocksIntersectEntity(const sSetBlockVector & a_Blocks);
+
 	// tolua_begin
 
 	/** Returns wheter the player can fly or not. */
-- 
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