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cuberite-2a/src/Tracer.cpp

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C++
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#include "Globals.h" // NOTE: MSVC stupidness requires this to be the same across all modules
#include "Tracer.h"
#include "World.h"
#include "Vector3f.h"
#include "Vector3i.h"
#include "Vector3d.h"
#include "Entities/Entity.h"
#ifndef _WIN32
#include <stdlib.h> // abs()
#endif
cTracer::cTracer(cWorld * a_World)
: m_World(a_World)
{
m_NormalTable[0].Set(-1, 0, 0);
m_NormalTable[1].Set( 0, 0,-1);
m_NormalTable[2].Set( 1, 0, 0);
m_NormalTable[3].Set( 0, 0, 1);
m_NormalTable[4].Set( 0, 1, 0);
m_NormalTable[5].Set( 0,-1, 0);
}
cTracer::~cTracer()
{
}
float cTracer::SigNum( float a_Num )
{
if (a_Num < 0.f) return -1.f;
if (a_Num > 0.f) return 1.f;
return 0.f;
}
void cTracer::SetValues(const Vector3f & a_Start, const Vector3f & a_Direction)
{
// calculate the direction of the ray (linear algebra)
dir = a_Direction;
// decide which direction to start walking in
step.x = (int) SigNum(dir.x);
step.y = (int) SigNum(dir.y);
step.z = (int) SigNum(dir.z);
// normalize the direction vector
if( dir.SqrLength() > 0.f ) dir.Normalize();
// how far we must move in the ray direction before
// we encounter a new voxel in x-direction
// same but y-direction
if (dir.x != 0.f)
{
tDelta.x = 1 / fabs(dir.x);
}
else
{
tDelta.x = 0;
}
if (dir.y != 0.f)
{
tDelta.y = 1 / fabs(dir.y);
}
else
{
tDelta.y = 0;
}
if (dir.z != 0.f)
{
tDelta.z = 1 / fabs(dir.z);
}
else
{
tDelta.z = 0;
}
// start voxel coordinates
pos.x = (int)floorf(a_Start.x);
pos.y = (int)floorf(a_Start.y);
pos.z = (int)floorf(a_Start.z);
// calculate distance to first intersection in the voxel we start from
if (dir.x < 0)
{
tMax.x = ((float)pos.x - a_Start.x) / dir.x;
}
else
{
tMax.x = (((float)pos.x + 1) - a_Start.x) / dir.x;
}
if (dir.y < 0)
{
tMax.y = ((float)pos.y - a_Start.y) / dir.y;
}
else
{
tMax.y = (((float)pos.y + 1) - a_Start.y) / dir.y;
}
if (dir.z < 0)
{
tMax.z = ((float)pos.z - a_Start.z) / dir.z;
}
else
{
tMax.z = (((float)pos.z + 1) - a_Start.z) / dir.z;
}
}
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bool cTracer::Trace( const Vector3f & a_Start, const Vector3f & a_Direction, int a_Distance, bool a_LineOfSight)
{
if ((a_Start.y < 0) || (a_Start.y >= cChunkDef::Height))
{
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LOGD("%s: Start Y is outside the world (%.2f), not tracing.", __FUNCTION__, a_Start.y);
return false;
}
SetValues(a_Start, a_Direction);
Vector3f End = a_Start + (dir * (float)a_Distance);
if (End.y < 0)
{
float dist = -a_Start.y / dir.y;
End = a_Start + (dir * dist);
}
// end voxel coordinates
end1.x = (int)floorf(End.x);
end1.y = (int)floorf(End.y);
end1.z = (int)floorf(End.z);
// check if first is occupied
if (pos.Equals(end1))
{
return false;
}
bool reachedX = false, reachedY = false, reachedZ = false;
int Iterations = 0;
while (Iterations < a_Distance)
{
Iterations++;
if ((tMax.x < tMax.y) && (tMax.x < tMax.z))
{
tMax.x += tDelta.x;
pos.x += step.x;
}
else if (tMax.y < tMax.z)
{
tMax.y += tDelta.y;
pos.y += step.y;
}
else
{
tMax.z += tDelta.z;
pos.z += step.z;
}
if (step.x > 0.0f)
{
if (pos.x >= end1.x)
{
reachedX = true;
}
}
else if (pos.x <= end1.x)
{
reachedX = true;
}
if (step.y > 0.0f)
{
if(pos.y >= end1.y)
{
reachedY = true;
}
}
else if (pos.y <= end1.y)
{
reachedY = true;
}
if (step.z > 0.0f)
{
if (pos.z >= end1.z)
{
reachedZ = true;
}
}
else if (pos.z <= end1.z)
{
reachedZ = true;
}
if (reachedX && reachedY && reachedZ)
{
return false;
}
BLOCKTYPE BlockID = m_World->GetBlock(pos.x, pos.y, pos.z);
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// Block is counted as a collision if we are not doing a line of sight and it is solid,
// or if the block is not air and not water. That way mobs can still see underwater.
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if ((!a_LineOfSight && cBlockInfo::IsSolid(BlockID)) || (a_LineOfSight && (BlockID != E_BLOCK_AIR) && !IsBlockWater(BlockID)))
{
BlockHitPosition = pos;
int Normal = GetHitNormal(a_Start, End, pos );
if(Normal > 0)
{
HitNormal = m_NormalTable[Normal-1];
}
return true;
}
}
return false;
}
// return 1 = hit, other is not hit
int LinesCross(float x0,float y0,float x1,float y1,float x2,float y2,float x3,float y3)
{
//float linx, liny;
float d=(x1-x0)*(y3-y2)-(y1-y0)*(x3-x2);
if (abs(d)<0.001) {return 0;}
float AB=((y0-y2)*(x3-x2)-(x0-x2)*(y3-y2))/d;
if (AB>=0.0 && AB<=1.0)
{
float CD=((y0-y2)*(x1-x0)-(x0-x2)*(y1-y0))/d;
if (CD>=0.0 && CD<=1.0)
{
//linx=x0+AB*(x1-x0);
//liny=y0+AB*(y1-y0);
return 1;
}
}
return 0;
}
// intersect3D_SegmentPlane(): intersect a segment and a plane
// Input: a_Ray = a segment, and a_Plane = a plane = {Point V0; Vector n;}
// Output: *I0 = the intersect point (when it exists)
// Return: 0 = disjoint (no intersection)
// 1 = intersection in the unique point *I0
// 2 = the segment lies in the plane
int cTracer::intersect3D_SegmentPlane( const Vector3f & a_Origin, const Vector3f & a_End, const Vector3f & a_PlanePos, const Vector3f & a_PlaneNormal )
{
Vector3f u = a_End - a_Origin;//a_Ray.P1 - S.P0;
Vector3f w = a_Origin - a_PlanePos;//S.P0 - Pn.V0;
float D = a_PlaneNormal.Dot( u );//dot(Pn.n, u);
float N = -(a_PlaneNormal.Dot( w ) );//-dot(a_Plane.n, w);
const float EPSILON = 0.0001f;
if (fabs(D) < EPSILON) { // segment is parallel to plane
if (N == 0) // segment lies in plane
return 2;
return 0; // no intersection
}
// they are not parallel
// compute intersect param
float sI = N / D;
if (sI < 0 || sI > 1)
return 0; // no intersection
//Vector3f I ( a_Ray->GetOrigin() + sI * u );//S.P0 + sI * u; // compute segment intersect point
RealHit = a_Origin + u * sI;
return 1;
}
int cTracer::GetHitNormal(const Vector3f & start, const Vector3f & end, const Vector3i & a_BlockPos)
{
Vector3i SmallBlockPos = a_BlockPos;
char BlockID = m_World->GetBlock( a_BlockPos.x, a_BlockPos.y, a_BlockPos.z );
if( BlockID == E_BLOCK_AIR || IsBlockWater(BlockID))
return 0;
Vector3f BlockPos;
BlockPos = Vector3f(SmallBlockPos);
Vector3f Look = (end - start);
Look.Normalize();
float dot = Look.Dot( Vector3f(-1, 0, 0) ); // first face normal is x -1
if(dot < 0)
{
int Lines = LinesCross( start.x, start.y, end.x, end.y, BlockPos.x, BlockPos.y, BlockPos.x, BlockPos.y + 1 );
if(Lines == 1)
{
Lines = LinesCross( start.x, start.z, end.x, end.z, BlockPos.x, BlockPos.z, BlockPos.x, BlockPos.z + 1 );
if(Lines == 1)
{
intersect3D_SegmentPlane( start, end, BlockPos, Vector3f(-1, 0, 0) );
return 1;
}
}
}
dot = Look.Dot( Vector3f(0, 0, -1) ); // second face normal is z -1
if(dot < 0)
{
int Lines = LinesCross( start.z, start.y, end.z, end.y, BlockPos.z, BlockPos.y, BlockPos.z, BlockPos.y + 1 );
if(Lines == 1)
{
Lines = LinesCross( start.z, start.x, end.z, end.x, BlockPos.z, BlockPos.x, BlockPos.z, BlockPos.x + 1 );
if(Lines == 1)
{
intersect3D_SegmentPlane( start, end, BlockPos, Vector3f(0, 0, -1) );
return 2;
}
}
}
dot = Look.Dot( Vector3f(1, 0, 0) ); // third face normal is x 1
if(dot < 0)
{
int Lines = LinesCross( start.x, start.y, end.x, end.y, BlockPos.x + 1, BlockPos.y, BlockPos.x + 1, BlockPos.y + 1 );
if(Lines == 1)
{
Lines = LinesCross( start.x, start.z, end.x, end.z, BlockPos.x + 1, BlockPos.z, BlockPos.x + 1, BlockPos.z + 1 );
if(Lines == 1)
{
intersect3D_SegmentPlane( start, end, BlockPos + Vector3f(1, 0, 0), Vector3f(1, 0, 0) );
return 3;
}
}
}
dot = Look.Dot( Vector3f(0, 0, 1) ); // fourth face normal is z 1
if(dot < 0)
{
int Lines = LinesCross( start.z, start.y, end.z, end.y, BlockPos.z + 1, BlockPos.y, BlockPos.z + 1, BlockPos.y + 1 );
if(Lines == 1)
{
Lines = LinesCross( start.z, start.x, end.z, end.x, BlockPos.z + 1, BlockPos.x, BlockPos.z + 1, BlockPos.x + 1 );
if(Lines == 1)
{
intersect3D_SegmentPlane( start, end, BlockPos + Vector3f(0, 0, 1), Vector3f(0, 0, 1) );
return 4;
}
}
}
dot = Look.Dot( Vector3f(0, 1, 0) ); // fifth face normal is y 1
if(dot < 0)
{
int Lines = LinesCross( start.y, start.x, end.y, end.x, BlockPos.y + 1, BlockPos.x, BlockPos.y + 1, BlockPos.x + 1 );
if(Lines == 1)
{
Lines = LinesCross( start.y, start.z, end.y, end.z, BlockPos.y + 1, BlockPos.z, BlockPos.y + 1, BlockPos.z + 1 );
if(Lines == 1)
{
intersect3D_SegmentPlane( start, end, BlockPos + Vector3f(0, 1, 0), Vector3f(0, 1, 0) );
return 5;
}
}
}
dot = Look.Dot( Vector3f(0, -1, 0) ); // sixth face normal is y -1
if(dot < 0)
{
int Lines = LinesCross( start.y, start.x, end.y, end.x, BlockPos.y, BlockPos.x, BlockPos.y, BlockPos.x + 1 );
if(Lines == 1)
{
Lines = LinesCross( start.y, start.z, end.y, end.z, BlockPos.y, BlockPos.z, BlockPos.y, BlockPos.z + 1 );
if(Lines == 1)
{
intersect3D_SegmentPlane( start, end, BlockPos, Vector3f(0, -1, 0) );
return 6;
}
}
}
return 0;
}