box.cc

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/*
 * Copyright (c) 2009 Dan Broyles
 *
 * SPDX-License-Identifier: GPL-2.0-only
 *
 * Author: Dan Broyles <dbroyl01@ku.edu>
 */
 
#include "box.h"
 
#include "ns3/assert.h"
#include "ns3/fatal-error.h"
#include "ns3/vector.h"
 
#include <algorithm>
#include <cmath>
#include <sstream>
 
namespace ns3
{
 
Box::Box(double _xMin, double _xMax, double _yMin, double _yMax, double _zMin, double _zMax)
    : xMin(_xMin),
      xMax(_xMax),
      yMin(_yMin),
      yMax(_yMax),
      zMin(_zMin),
      zMax(_zMax)
{
}
 
Box::Box()
    : xMin(0.0),
      xMax(0.0),
      yMin(0.0),
      yMax(0.0),
      zMin(0.0),
      zMax(0.0)
{
}
 
bool
Box::IsInside(const Vector& position) const
{
    return position.x <= this->xMax && position.x >= this->xMin && position.y <= this->yMax &&
           position.y >= this->yMin && position.z <= this->zMax && position.z >= this->zMin;
}
 
Box::Side
Box::GetClosestSide(const Vector& position) const
{
    double xMinDist = std::abs(position.x - this->xMin);
    double xMaxDist = std::abs(this->xMax - position.x);
    double yMinDist = std::abs(position.y - this->yMin);
    double yMaxDist = std::abs(this->yMax - position.y);
    double zMinDist = std::abs(position.z - this->zMin);
    double zMaxDist = std::abs(this->zMax - position.z);
    double minX = std::min(xMinDist, xMaxDist);
    double minY = std::min(yMinDist, yMaxDist);
    double minZ = std::min(zMinDist, zMaxDist);
    if (minX < minY && minX < minZ)
    {
        if (xMinDist < xMaxDist)
        {
            return LEFT;
        }
        else
        {
            return RIGHT;
        }
    }
    else if (minY < minZ)
    {
        if (yMinDist < yMaxDist)
        {
            return BOTTOM;
        }
        else
        {
            return TOP;
        }
    }
    else
    {
        if (zMinDist < zMaxDist)
        {
            return DOWN;
        }
        else
        {
            return UP;
        }
    }
}
 
Vector
Box::CalculateIntersection(const Vector& current, const Vector& speed) const
{
    NS_ASSERT(IsInside(current));
    double xMaxY = current.y + (this->xMax - current.x) / speed.x * speed.y;
    double xMinY = current.y + (this->xMin - current.x) / speed.x * speed.y;
    double yMaxX = current.x + (this->yMax - current.y) / speed.y * speed.x;
    double yMinX = current.x + (this->yMin - current.y) / speed.y * speed.x;
    bool xMaxYOk = (xMaxY <= this->yMax && xMaxY >= this->yMin);
    bool xMinYOk = (xMinY <= this->yMax && xMinY >= this->yMin);
    bool yMaxXOk = (yMaxX <= this->xMax && yMaxX >= this->xMin);
    bool yMinXOk = (yMinX <= this->xMax && yMinX >= this->xMin);
    if (xMaxYOk && speed.x >= 0)
    {
        return Vector(this->xMax, xMaxY, 0.0);
    }
    else if (xMinYOk && speed.x <= 0)
    {
        return Vector(this->xMin, xMinY, 0.0);
    }
    else if (yMaxXOk && speed.y >= 0)
    {
        return Vector(yMaxX, this->yMax, 0.0);
    }
    else if (yMinXOk && speed.y <= 0)
    {
        return Vector(yMinX, this->yMin, 0.0);
    }
    else
    {
        NS_ASSERT(false);
        // quiet compiler
        return Vector(0.0, 0.0, 0.0);
    }
}
 
bool
Box::IsIntersect(const Vector& l1, const Vector& l2) const
{
    // If any of the position falls inside the box,
    // return true.
    if (IsInside(l1) || IsInside(l2))
    {
        return true;
    }
 
    Vector boxSize(0.5 * (this->xMax - this->xMin),
                   0.5 * (this->yMax - this->yMin),
                   0.5 * (this->zMax - this->zMin));
    Vector boxCenter(this->xMin + boxSize.x, this->yMin + boxSize.y, this->zMin + boxSize.z);
 
    // Put line-segment in box space
    Vector lB1(l1.x - boxCenter.x, l1.y - boxCenter.y, l1.z - boxCenter.z);
    Vector lB2(l2.x - boxCenter.x, l2.y - boxCenter.y, l2.z - boxCenter.z);
 
    // Get line-segment midpoint and extent
    Vector lMid(0.5 * (lB1.x + lB2.x), 0.5 * (lB1.y + lB2.y), 0.5 * (lB1.z + lB2.z));
    Vector l(lB1.x - lMid.x, lB1.y - lMid.y, lB1.z - lMid.z);
    Vector lExt(std::abs(l.x), std::abs(l.y), std::abs(l.z));
 
    // Use Separating Axis Test
    // Separation vector from box center to line-segment center is lMid, since the
    // line is in box space, if any dimension of the line-segment did not intersect
    // the box, return false, which means the whole line-segment didn't
    // intersect the box.
    if (std::abs(lMid.x) > boxSize.x + lExt.x)
    {
        return false;
    }
    if (std::abs(lMid.y) > boxSize.y + lExt.y)
    {
        return false;
    }
    if (std::abs(lMid.z) > boxSize.z + lExt.z)
    {
        return false;
    }
    // Cross-products of line and each axis
    if (std::abs(lMid.y * l.z - lMid.z * l.y) > (boxSize.y * lExt.z + boxSize.z * lExt.y))
    {
        return false;
    }
    if (std::abs(lMid.x * l.z - lMid.z * l.x) > (boxSize.x * lExt.z + boxSize.z * lExt.x))
    {
        return false;
    }
    if (std::abs(lMid.x * l.y - lMid.y * l.x) > (boxSize.x * lExt.y + boxSize.y * lExt.x))
    {
        return false;
    }
 
    // No separating axis, the line-segment intersect this box, return true.
    return true;
}
 
ATTRIBUTE_HELPER_CPP(Box);
 
/**
 * \brief Stream insertion operator.
 *
 * \param os the stream
 * \param box the box
 * \returns a reference to the stream
 */
std::ostream&
operator<<(std::ostream& os, const Box& box)
{
    os << box.xMin << "|" << box.xMax << "|" << box.yMin << "|" << box.yMax << "|" << box.zMin
       << "|" << box.zMax;
    return os;
}
 
/**
 * \brief Stream extraction operator.
 *
 * \param is the stream
 * \param box the box
 * \returns a reference to the stream
 */
std::istream&
operator>>(std::istream& is, Box& box)
{
    char c1;
    char c2;
    char c3;
    char c4;
    char c5;
    is >> box.xMin >> c1 >> box.xMax >> c2 >> box.yMin >> c3 >> box.yMax >> c4 >> box.zMin >> c5 >>
        box.zMax;
    if (c1 != '|' || c2 != '|' || c3 != '|' || c4 != '|' || c5 != '|')
    {
        is.setstate(std::ios_base::failbit);
    }
    return is;
}
 
} // namespace ns3