cuberite-2a/source/cTracer.cpp

#include "Globals.h"  // NOTE: MSVC stupidness requires this to be the same across all modules

#include "cTracer.h"
#include "cWorld.h"

#include "Vector3f.h"
#include "Vector3i.h"
#include "Vector3d.h"

#include "BlockID.h"
#include "cEntity.h"

#include "Defines.h"

#ifndef _WIN32
	#include <stdlib.h> // abs()
#endif

cTracer::cTracer(cWorld* a_World)
	: m_World( a_World )
{
	m_NormalTable[0] = new Vector3f(-1, 0, 0);
	m_NormalTable[1] = new Vector3f( 0, 0,-1);
	m_NormalTable[2] = new Vector3f( 1, 0, 0);
	m_NormalTable[3] = new Vector3f( 0, 0, 1);
	m_NormalTable[4] = new Vector3f( 0, 1, 0);
	m_NormalTable[5] = new Vector3f( 0,-1, 0);

	DotPos = new Vector3f();
	BoxOffset = new Vector3f();
	BlockHitPosition = new Vector3f();
	HitNormal = new Vector3f();
	RealHit = new Vector3f();


	dir = new Vector3f();
	tDelta = new Vector3f();
	pos =  new Vector3i();
	end1 = new Vector3i();
	step = new Vector3i();
	tMax = new Vector3f();
}

cTracer::~cTracer()
{
	for( int i = 0; i < 6; ++i )
	{
		delete m_NormalTable[i];
		m_NormalTable[i] = 0;
	}

	delete DotPos;				DotPos = 0;
	delete BoxOffset;			BoxOffset = 0;
	delete BlockHitPosition;	BlockHitPosition = 0;
	delete HitNormal;			HitNormal = 0;
	delete RealHit;				RealHit = 0;

	delete dir;					dir = 0;
	delete tDelta;				tDelta = 0;
	delete pos;					pos = 0;
	delete end1;				end1 = 0;
	delete step;				step = 0;
	delete tMax;				tMax = 0;
}

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
	// use your
	// transformer
	// function here
	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;
	}
}

int cTracer::Trace( const Vector3f & a_Start, const Vector3f & a_Direction, int a_Distance)
{
	SetValues( a_Start, a_Direction );

	const Vector3f End = a_Start + ((*dir) * (float)a_Distance);

	// 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 ) )
	{
		LOG("WARNING: cTracer: Start and end in same block");
		return 0;
	}

	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;
		}
		
		char BlockID = m_World->GetBlock( pos->x, pos->y, pos->z );
		//No collision with water ;)
		if ( BlockID != E_BLOCK_AIR || IsBlockWater(BlockID))
		{
			*BlockHitPosition = pos;
			int Normal = GetHitNormal(a_Start, End, *pos );
			if(Normal > 0)
			{
				*HitNormal = *m_NormalTable[Normal-1];
			}
			return 1;
		}
	}
	return 0;
}

// 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;
}