1 files changed, 365 insertions, 0 deletions
diff --git a/src/Mobs/Path.cpp b/src/Mobs/Path.cpp
new file mode 100644
index 000000000..8abbc4cac
--- /dev/null
+++ b/src/Mobs/Path.cpp
@@ -0,0 +1,365 @@
+
+#include "Globals.h"
+
+#include <cmath>
+
+#include "Path.h"
+#include "../Chunk.h"
+
+#define DISTANCE_MANHATTAN 0  // 1: More speed, a bit less accuracy 0: Max accuracy, less speed.
+#define HEURISTICS_ONLY 0  // 1: Much more speed, much less accurate.
+#define CALCULATIONS_PER_STEP 60  // Higher means more CPU load but faster path calculations.
+// The only version which guarantees the shortest path is 0, 0.
+
+enum class eCellStatus {OPENLIST,  CLOSEDLIST,  NOLIST};
+struct cPathCell
+{
+	Vector3i m_Location;   // Location of the cell in the world.
+	int m_F, m_G, m_H;  // F, G, H as defined in regular A*.
+	eCellStatus m_Status;  // Which list is the cell in? Either non, open, or closed.
+	cPathCell * m_Parent;  // Cell's parent, as defined in regular A*.
+	bool m_IsSolid;	   // Is the cell an air or a solid? Partial solids are currently considered solids.
+};
+
+
+
+
+
+bool compareHeuristics::operator()(cPathCell * & a_Cell1, cPathCell * & a_Cell2)
+{
+	return a_Cell1->m_F > a_Cell2->m_F;
+}
+
+
+
+
+
+/* cPath implementation */
+cPath::cPath(
+	cChunk & a_Chunk,
+	const Vector3i & a_StartingPoint, const Vector3i & a_EndingPoint, int a_MaxSteps,
+	double a_BoundingBoxWidth, double a_BoundingBoxHeight,
+	int a_MaxUp, int a_MaxDown
+) :
+	m_Destination(a_EndingPoint.Floor()),
+	m_Source(a_StartingPoint.Floor()),
+	m_CurrentPoint(0),  // GetNextPoint increments this to 1, but that's fine, since the first cell is always a_StartingPoint
+	m_Chunk(&a_Chunk)
+{
+	// TODO: if src not walkable OR dest not walkable, then abort.
+	// Borrow a new "isWalkable" from ProcessIfWalkable, make ProcessIfWalkable also call isWalkable
+
+	if (GetCell(m_Source)->m_IsSolid || GetCell(m_Destination)->m_IsSolid)
+	{
+		m_Status = ePathFinderStatus::PATH_NOT_FOUND;
+		return;
+	}
+
+	m_Status = ePathFinderStatus::CALCULATING;
+	m_StepsLeft = a_MaxSteps;
+
+	ProcessCell(GetCell(a_StartingPoint), nullptr, 0);
+	m_Chunk = nullptr;
+}
+
+
+
+
+
+cPath::~cPath()
+{
+	if (m_Status == ePathFinderStatus::CALCULATING)
+	{
+		FinishCalculation();
+	}
+}
+
+
+
+
+
+ePathFinderStatus cPath::Step(cChunk & a_Chunk)
+{
+	m_Chunk = &a_Chunk;
+
+	if (m_Status != ePathFinderStatus::CALCULATING)
+	{
+		return m_Status;
+	}
+
+	if (m_StepsLeft == 0)
+	{
+		FinishCalculation(ePathFinderStatus::PATH_NOT_FOUND);
+	}
+	else
+	{
+		--m_StepsLeft;
+		int i;
+		for (i = 0; i < CALCULATIONS_PER_STEP; ++i)
+		{
+			if (Step_Internal())  // Step_Internal returns true when no more calculation is needed.
+			{
+				break;  // if we're here, m_Status must have changed either to PATH_FOUND or PATH_NOT_FOUND.
+			}
+		}
+	}
+
+	m_Chunk = nullptr;
+	return m_Status;
+}
+
+
+
+
+
+bool cPath::IsSolid(const Vector3i & a_Location)
+{
+	ASSERT(m_Chunk != nullptr);
+
+	auto Chunk = m_Chunk->GetNeighborChunk(a_Location.x, a_Location.z);
+	if ((Chunk == nullptr) || !Chunk->IsValid())
+	{
+		return true;
+	}
+	m_Chunk = Chunk;
+
+	BLOCKTYPE BlockType;
+	NIBBLETYPE BlockMeta;
+	int RelX = a_Location.x - m_Chunk->GetPosX() * cChunkDef::Width;
+	int RelZ = a_Location.z - m_Chunk->GetPosZ() * cChunkDef::Width;
+
+	m_Chunk->GetBlockTypeMeta(RelX, a_Location.y, RelZ, BlockType, BlockMeta);
+	if ((BlockType == E_BLOCK_FENCE) || (BlockType == E_BLOCK_FENCE_GATE))
+	{
+		GetCell(a_Location + Vector3i(0, 1, 0))->m_IsSolid = true;  // Mobs will always think that the fence is 2 blocks high and therefore won't jump over.
+	}
+	if (BlockType == E_BLOCK_STATIONARY_WATER)
+	{
+		GetCell(a_Location + Vector3i(0, -1, 0))->m_IsSolid = true;  // Mobs will always think that the fence is 2 blocks high and therefore won't jump over.
+	}
+
+	return cBlockInfo::IsSolid(BlockType);
+}
+
+
+
+
+
+bool cPath::Step_Internal()
+{
+	cPathCell * CurrentCell = OpenListPop();
+
+	// Path not reachable, open list exauhsted.
+	if (CurrentCell == nullptr)
+	{
+		FinishCalculation(ePathFinderStatus::PATH_NOT_FOUND);
+		ASSERT(m_Status == ePathFinderStatus::PATH_NOT_FOUND);
+		return true;
+	}
+
+	// Path found.
+	if (
+			(CurrentCell->m_Location == m_Destination + Vector3i(0, 0, 1)) ||
+			(CurrentCell->m_Location == m_Destination + Vector3i(1, 0, 0)) ||
+			(CurrentCell->m_Location == m_Destination + Vector3i(-1, 0, 0)) ||
+			(CurrentCell->m_Location == m_Destination + Vector3i(0, 0, -1)) ||
+			(CurrentCell->m_Location == m_Destination + Vector3i(0, -1, 0))
+	)
+	{
+		do
+		{
+			m_PathPoints.push_back(CurrentCell->m_Location);  // Populate the cPath with points.
+			CurrentCell = CurrentCell->m_Parent;
+		} while (CurrentCell != nullptr);
+
+		FinishCalculation(ePathFinderStatus::PATH_FOUND);
+		return true;
+	}
+
+	// Calculation not finished yet, process a currentCell by inspecting all neighbors.
+
+	// Check North, South, East, West on all 3 different heights.
+	int i;
+	for (i = -1; i <= 1; ++i)
+	{
+		ProcessIfWalkable(CurrentCell->m_Location + Vector3i(1, i, 0),  CurrentCell, 10);
+		ProcessIfWalkable(CurrentCell->m_Location + Vector3i(-1, i, 0), CurrentCell, 10);
+		ProcessIfWalkable(CurrentCell->m_Location + Vector3i(0, i, 1),  CurrentCell, 10);
+		ProcessIfWalkable(CurrentCell->m_Location + Vector3i(0, i, -1), CurrentCell, 10);
+	}
+
+	// Check diagonals on mob's height only.
+	int x, z;
+	for (x = -1; x <= 1; x += 2)
+	{
+		for (z = -1; z <= 1; z += 2)
+		{
+			// This condition prevents diagonal corner cutting.
+			if (!GetCell(CurrentCell->m_Location + Vector3i(x, 0, 0))->m_IsSolid && !GetCell(CurrentCell->m_Location + Vector3i(0, 0, z))->m_IsSolid)
+			{
+				// This prevents falling of "sharp turns" e.g. a 1x1x20 rectangle in the air which breaks in a right angle suddenly.
+				if (GetCell(CurrentCell->m_Location + Vector3i(x, -1, 0))->m_IsSolid && GetCell(CurrentCell->m_Location + Vector3i(0, -1, z))->m_IsSolid)
+				{
+					ProcessIfWalkable(CurrentCell->m_Location + Vector3i(x, 0, z), CurrentCell, 14);  // 14 is a good enough approximation of sqrt(10 + 10).
+				}
+			}
+		}
+	}
+
+	return false;
+}
+
+
+
+
+
+void cPath::FinishCalculation()
+{
+	for (auto && pair : m_Map)
+	{
+		delete pair.second;
+	}
+
+	m_Map.clear();
+	m_OpenList = std::priority_queue<cPathCell *, std::vector<cPathCell *>, compareHeuristics>{};
+}
+
+
+
+
+
+void cPath::FinishCalculation(ePathFinderStatus a_NewStatus)
+{
+	m_Status = a_NewStatus;
+	FinishCalculation();
+}
+
+
+
+
+
+void cPath::OpenListAdd(cPathCell * a_Cell)
+{
+	a_Cell->m_Status = eCellStatus::OPENLIST;
+	m_OpenList.push(a_Cell);
+	#ifdef COMPILING_PATHFIND_DEBUGGER
+	si::setBlock(a_Cell->m_Location.x, a_Cell->m_Location.y, a_Cell->m_Location.z, debug_open, SetMini(a_Cell));
+	#endif
+}
+
+
+
+
+
+cPathCell * cPath::OpenListPop()  // Popping from the open list also means adding to the closed list.
+{
+	if (m_OpenList.size() == 0)
+	{
+		return nullptr;  // We've exhausted the search space and nothing was found, this will trigger a PATH_NOT_FOUND status.
+	}
+
+	cPathCell * Ret = m_OpenList.top();
+	m_OpenList.pop();
+	Ret->m_Status = eCellStatus::CLOSEDLIST;
+	#ifdef COMPILING_PATHFIND_DEBUGGER
+si::setBlock((Ret)->m_Location.x, (Ret)->m_Location.y, (Ret)->m_Location.z, debug_closed, SetMini(Ret));
+	#endif
+	return Ret;
+}
+
+
+
+
+
+void cPath::ProcessIfWalkable(const Vector3i & a_Location, cPathCell * a_Parent, int a_Cost)
+{
+	cPathCell * cell = GetCell(a_Location);
+	if (!cell->m_IsSolid && GetCell(a_Location + Vector3i(0, -1, 0))->m_IsSolid && !GetCell(a_Location + Vector3i(0, 1, 0))->m_IsSolid)
+	{
+		ProcessCell(cell, a_Parent, a_Cost);
+	}
+}
+
+
+
+
+
+void cPath::ProcessCell(cPathCell * a_Cell, cPathCell * a_Caller, int a_GDelta)
+{
+	// Case 1: Cell is in the closed list, ignore it.
+	if (a_Cell->m_Status == eCellStatus::CLOSEDLIST)
+	{
+		return;
+	}
+	if (a_Cell->m_Status == eCellStatus::NOLIST)  // Case 2: The cell is not in any list.
+	{
+		// Cell is walkable, add it to the open list.
+		// Note that non-walkable cells are filtered out in Step_internal();
+		// Special case: Start cell goes here, gDelta is 0, caller is NULL.
+		a_Cell->m_Parent = a_Caller;
+		if (a_Caller != nullptr)
+		{
+			a_Cell->m_G = a_Caller->m_G + a_GDelta;
+		}
+		else
+		{
+			a_Cell->m_G = 0;
+		}
+
+		// Calculate H. This is A*'s Heuristics value.
+		#if DISTANCE_MANHATTAN == 1
+			// Manhattan distance. DeltaX + DeltaY + DeltaZ.
+			a_Cell->m_H = 10 * (abs(a_Cell->m_Location.x-m_Destination.x) + abs(a_Cell->m_Location.y-m_Destination.y) + abs(a_Cell->m_Location.z-m_Destination.z));
+		#else
+			// Euclidian distance. sqrt(DeltaX^2 + DeltaY^2 + DeltaZ^2), more precise.
+			a_Cell->m_H = static_cast<decltype(a_Cell->m_H)>((a_Cell->m_Location - m_Destination).Length() * 10);
+		#endif
+
+		#if HEURISTICS_ONLY == 1
+			a_Cell->m_F = a_Cell->m_H;  // Greedy search. https://en.wikipedia.org/wiki/Greedy_search
+		#else
+			a_Cell->m_F = a_Cell->m_H + a_Cell->m_G;  // Regular A*.
+		#endif
+
+		OpenListAdd(a_Cell);
+		return;
+	}
+
+	// Case 3: Cell is in the open list, check if G and H need an update.
+	int NewG = a_Caller->m_G + a_GDelta;
+	if (NewG < a_Cell->m_G)
+	{
+		a_Cell->m_G = NewG;
+		a_Cell->m_H = a_Cell->m_F + a_Cell->m_G;
+		a_Cell->m_Parent = a_Caller;
+	}
+
+}
+
+
+
+
+
+cPathCell * cPath::GetCell(const Vector3i & a_Location)
+{
+	// Create the cell in the hash table if it's not already there.
+	cPathCell * Cell;
+	if (m_Map.count(a_Location) == 0)  // Case 1: Cell is not on any list. We've never checked this cell before.
+	{
+		Cell = new cPathCell();
+		Cell->m_Location = a_Location;
+		m_Map[a_Location] = Cell;
+		Cell->m_IsSolid = IsSolid(a_Location);
+		Cell->m_Status = eCellStatus::NOLIST;
+		#ifdef COMPILING_PATHFIND_DEBUGGER
+			#ifdef COMPILING_PATHFIND_DEBUGGER_MARK_UNCHECKED
+				si::setBlock(a_Location.x, a_Location.y, a_Location.z, debug_unchecked, Cell->m_IsSolid ? NORMAL : MINI);
+			#endif
+		#endif
+		return Cell;
+	}
+	else
+	{
+		return m_Map[a_Location];
+	}
+}