LineBlockTracer.cpp

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// LineBlockTracer.cpp
 
// Implements the cLineBlockTracer class representing a cBlockTracer that traces along a straight line between two points
 
#include "Globals.h"
#include "LineBlockTracer.h"
#include "BlockInfo.h"
#include "World.h"
#include "Chunk.h"
#include "BoundingBox.h"
 
 
 
 
 
cLineBlockTracer::cLineBlockTracer(cWorld & a_World, cCallbacks & a_Callbacks) :
    Super(a_World, a_Callbacks),
    m_Start(),
    m_End(),
    m_Diff(),
    m_Dir(),
    m_Current(),
    m_CurrentFace(BLOCK_FACE_NONE)
{
}
 
 
 
 
 
bool cLineBlockTracer::Trace(cWorld & a_World, cBlockTracer::cCallbacks & a_Callbacks, const Vector3d a_Start, const Vector3d a_End)
{
    cLineBlockTracer Tracer(a_World, a_Callbacks);
    return Tracer.Trace(a_Start, a_End);
}
 
 
 
 
 
bool cLineBlockTracer::LineOfSightTrace(cWorld & a_World, const Vector3d & a_Start, const Vector3d & a_End, int a_Sight)
{
    static class LineOfSightCallbacks:
        public cLineBlockTracer::cCallbacks
    {
        bool m_IsAirOpaque;
        bool m_IsWaterOpaque;
        bool m_IsLavaOpaque;
    public:
        LineOfSightCallbacks(bool a_IsAirOpaque, bool a_IsWaterOpaque, bool a_IsLavaOpaque):
            m_IsAirOpaque(a_IsAirOpaque),
            m_IsWaterOpaque(a_IsWaterOpaque),
            m_IsLavaOpaque(a_IsLavaOpaque)
        {}
 
        virtual bool OnNextBlock(Vector3i a_BlockPos, BLOCKTYPE a_BlockType, NIBBLETYPE a_BlockMeta, eBlockFace a_EntryFace) override
        {
            switch (a_BlockType)
            {
                case E_BLOCK_AIR:              return m_IsAirOpaque;
                case E_BLOCK_LAVA:             return m_IsLavaOpaque;
                case E_BLOCK_STATIONARY_LAVA:  return m_IsLavaOpaque;
                case E_BLOCK_STATIONARY_WATER: return m_IsWaterOpaque;
                case E_BLOCK_WATER:            return m_IsWaterOpaque;
                default: return true;
            }
        }
    } callbacks(
        (a_Sight & losAir) == 0,
        (a_Sight & losWater) == 0,
        (a_Sight & losLava) == 0
    );
    return Trace(a_World, callbacks, a_Start, a_End);
}
 
 
 
 
 
bool cLineBlockTracer::FirstSolidHitTrace(
    cWorld & a_World,
    const Vector3d & a_Start, const Vector3d & a_End,
    Vector3d & a_HitCoords,
    Vector3i & a_HitBlockCoords, eBlockFace & a_HitBlockFace
)
{
    class cSolidHitCallbacks:
        public cCallbacks
    {
    public:
        cSolidHitCallbacks(const Vector3d & a_CBStart, const Vector3d & a_CBEnd, Vector3d & a_CBHitCoords, Vector3i & a_CBHitBlockCoords, eBlockFace & a_CBHitBlockFace):
            m_Start(a_CBStart),
            m_End(a_CBEnd),
            m_HitCoords(a_CBHitCoords),
            m_HitBlockCoords(a_CBHitBlockCoords),
            m_HitBlockFace(a_CBHitBlockFace)
        {
        }
 
        virtual bool OnNextBlock(Vector3i a_BlockPos, BLOCKTYPE a_BlockType, NIBBLETYPE a_BlockMeta, eBlockFace a_EntryFace) override
        {
            if (!cBlockInfo::IsSolid(a_BlockType))
            {
                return false;
            }
 
            // We hit a solid block, calculate the exact hit coords and abort trace:
            m_HitBlockCoords = a_BlockPos;
            m_HitBlockFace = a_EntryFace;
            cBoundingBox bb(a_BlockPos, a_BlockPos + Vector3i(1, 1, 1));  // Bounding box of the block hit
            double LineCoeff = 0;  // Used to calculate where along the line an intersection with the bounding box occurs
            eBlockFace Face;  // Face hit
            if (!bb.CalcLineIntersection(m_Start, m_End, LineCoeff, Face))
            {
                // Math rounding errors have caused the calculation to miss the block completely, assume immediate hit
                LineCoeff = 0;
            }
            m_HitCoords = m_Start + (m_End - m_Start) * LineCoeff;  // Point where projectile goes into the hit block
            return true;
        }
 
    protected:
        const Vector3d & m_Start;
        const Vector3d & m_End;
        Vector3d & m_HitCoords;
        Vector3i & m_HitBlockCoords;
        eBlockFace & m_HitBlockFace;
    } callbacks(a_Start, a_End, a_HitCoords, a_HitBlockCoords, a_HitBlockFace);
    return !Trace(a_World, callbacks, a_Start, a_End);
}
 
 
 
 
 
bool cLineBlockTracer::Trace(const Vector3d a_Start, const Vector3d a_End)
{
    // Initialize the member veriables:
    m_Start = a_Start;
    m_End = a_End;
    m_Dir.x = (m_Start.x < m_End.x) ? 1 : -1;
    m_Dir.y = (m_Start.y < m_End.y) ? 1 : -1;
    m_Dir.z = (m_Start.z < m_End.z) ? 1 : -1;
    m_CurrentFace = BLOCK_FACE_NONE;
 
    // Check the start coords, adjust into the world:
    if (m_Start.y < 0)
    {
        if (m_End.y < 0)
        {
            // Nothing to trace
            m_Callbacks->OnNoMoreHits();
            return true;
        }
        FixStartBelowWorld();
        m_Callbacks->OnIntoWorld(m_Start);
    }
    else if (m_Start.y >= cChunkDef::Height)
    {
        if (m_End.y >= cChunkDef::Height)
        {
            m_Callbacks->OnNoMoreHits();
            return true;
        }
        FixStartAboveWorld();
        m_Callbacks->OnIntoWorld(m_Start);
    }
 
    m_Current = m_Start.Floor();
 
    m_Diff = m_End -  m_Start;
 
    // The actual trace is handled with ChunkMapCS locked by calling our ChunkCallback for the specified chunk
    int BlockX = FloorC(m_Start.x);
    int BlockZ = FloorC(m_Start.z);
    int ChunkX, ChunkZ;
    cChunkDef::BlockToChunk(BlockX, BlockZ, ChunkX, ChunkZ);
    return m_World->DoWithChunk(ChunkX, ChunkZ, [this](cChunk & a_Chunk) { return ChunkCallback(&a_Chunk); });
}
 
 
 
 
 
void cLineBlockTracer::FixStartAboveWorld(void)
{
    // We must set the start Y to less than cChunkDef::Height so that it is considered inside the world later on
    // Therefore we use an EPS-offset from the height, as small as reasonably possible.
    const double Height = static_cast<double>(cChunkDef::Height) - 0.00001;
    CalcXZIntersection(Height, m_Start.x, m_Start.z);
    m_Start.y = Height;
}
 
 
 
 
 
void cLineBlockTracer::FixStartBelowWorld(void)
{
    CalcXZIntersection(0, m_Start.x, m_Start.z);
    m_Start.y = 0;
}
 
 
 
 
 
void cLineBlockTracer::CalcXZIntersection(double a_Y, double & a_IntersectX, double & a_IntersectZ)
{
    double Ratio = (m_Start.y - a_Y) / (m_Start.y - m_End.y);
    a_IntersectX = m_Start.x + (m_End.x - m_Start.x) * Ratio;
    a_IntersectZ = m_Start.z + (m_End.z - m_Start.z) * Ratio;
}
 
 
 
 
 
bool cLineBlockTracer::MoveToNextBlock(void)
{
    // Find out which of the current block's walls gets hit by the path:
    static const double EPS = 0.00001;
    enum
    {
        dirNONE,
        dirX,
        dirY,
        dirZ,
    } Direction = dirNONE;
 
    // Calculate the next YZ wall hit:
    double Coeff = 1;
    if (std::abs(m_Diff.x) > EPS)
    {
        double DestX = (m_Dir.x > 0) ? (m_Current.x + 1) : m_Current.x;
        double CoeffX = (DestX - m_Start.x) / m_Diff.x;
        if (CoeffX <= 1)  // We need to include equality for the last block in the trace
        {
            Coeff = CoeffX;
            Direction = dirX;
        }
    }
 
    // If the next XZ wall hit is closer, use it instead:
    if (std::abs(m_Diff.y) > EPS)
    {
        double DestY = (m_Dir.y > 0) ? (m_Current.y + 1) : m_Current.y;
        double CoeffY = (DestY - m_Start.y) / m_Diff.y;
        if (CoeffY <= Coeff)  // We need to include equality for the last block in the trace
        {
            Coeff = CoeffY;
            Direction = dirY;
        }
    }
 
    // If the next XY wall hit is closer, use it instead:
    if (std::abs(m_Diff.z) > EPS)
    {
        double DestZ = (m_Dir.z > 0) ? (m_Current.z + 1) : m_Current.z;
        double CoeffZ = (DestZ - m_Start.z) / m_Diff.z;
        if (CoeffZ <= Coeff)  // We need to include equality for the last block in the trace
        {
            Direction = dirZ;
        }
    }
 
    // Based on the wall hit, adjust the current coords
    switch (Direction)
    {
        case dirX:    m_Current.x += m_Dir.x; m_CurrentFace = (m_Dir.x > 0) ? BLOCK_FACE_XM : BLOCK_FACE_XP; break;
        case dirY:    m_Current.y += m_Dir.y; m_CurrentFace = (m_Dir.y > 0) ? BLOCK_FACE_YM : BLOCK_FACE_YP; break;
        case dirZ:    m_Current.z += m_Dir.z; m_CurrentFace = (m_Dir.z > 0) ? BLOCK_FACE_ZM : BLOCK_FACE_ZP; break;
        case dirNONE: return false;
    }
    return true;
}
 
 
 
 
 
bool cLineBlockTracer::ChunkCallback(cChunk * a_Chunk)
{
    ASSERT((m_Current.y >= 0) && (m_Current.y < cChunkDef::Height));  // This should be provided by FixStartAboveWorld() / FixStartBelowWorld()
 
    // This is the actual line tracing loop.
    for (;;)
    {
        // Our caller (DoWithChunk callback) should never give nothing:
        ASSERT(a_Chunk != nullptr);
 
        // Move to next block
        if (!MoveToNextBlock())
        {
            // We've reached the end
            m_Callbacks->OnNoMoreHits();
            return true;
        }
 
        if ((m_Current.y < 0) || (m_Current.y >= cChunkDef::Height))
        {
            // We've gone out of the world, that's the end of this trace
            double IntersectX, IntersectZ;
            CalcXZIntersection(m_Current.y, IntersectX, IntersectZ);
            if (m_Callbacks->OnOutOfWorld({IntersectX, double(m_Current.y), IntersectZ}))
            {
                // The callback terminated the trace
                return false;
            }
            m_Callbacks->OnNoMoreHits();
            return true;
        }
 
        // Update the current chunk
        a_Chunk = a_Chunk->GetNeighborChunk(m_Current.x, m_Current.z);
        if (a_Chunk == nullptr)
        {
            m_Callbacks->OnNoChunk();
            return false;
        }
 
        // Report the current block through the callbacks:
        if (a_Chunk->IsValid())
        {
            BLOCKTYPE BlockType;
            NIBBLETYPE BlockMeta;
            int RelX = m_Current.x - a_Chunk->GetPosX() * cChunkDef::Width;
            int RelZ = m_Current.z - a_Chunk->GetPosZ() * cChunkDef::Width;
            a_Chunk->GetBlockTypeMeta(RelX, m_Current.y, RelZ, BlockType, BlockMeta);
            if (m_Callbacks->OnNextBlock(m_Current, BlockType, BlockMeta, m_CurrentFace))
            {
                // The callback terminated the trace
                return false;
            }
        }
        else if (m_Callbacks->OnNextBlockNoData(m_Current, m_CurrentFace))
        {
            // The callback terminated the trace
            return false;
        }
    }
}