Original Hand Written Champion

#include "clDDA3.h"
#include "clReal.h"

clDDA3::clDDA3(const clVec3& pos, const clVec3& dir)
  : m_pos(pos)
  , m_dir(dir)
{
  // Calculate inverse direction
  m_invDir = clVec3::One() / dir;

  // Calculate integer direction
  m_iDir = { int(dir.x >= 0), int(dir.y >= 0), int(dir.z >= 0) };

  // Calculate integer position
  m_iPos = { (int)clFloor(pos.x), (int)clFloor(pos.y), (int)clFloor(pos.z) };
}

clVec3I& clDDA3::Step()
{
  // Calculate dimension cross distance
  clVec3 crossDist = (clVec3(m_iPos + m_iDir) - m_pos) * m_invDir;

  // Calculate first crossed dimension index
  int firstCross = ((crossDist.x >= crossDist.y) && (crossDist.z > crossDist.y)) | (((crossDist.x >= crossDist.z) && (crossDist.y >= crossDist.z)) << 1);

  // Step across next dimension
  switch (firstCross)
  {
  case 0:
    m_iPos.x += (m_iDir.x << 1) - 1;
    m_pos += m_dir * crossDist.x;
    break;
  case 1:
    m_iPos.y += (m_iDir.y << 1) - 1;
    m_pos += m_dir * crossDist.y;
    break;
  case 2:
    m_iPos.z += (m_iDir.z << 1) - 1;
    m_pos += m_dir * crossDist.z;
    break;
  }
  return m_iPos;
}

clVec3 clDDA3::Position()
{
  return m_pos;
}