zeus/src/COBBox.cpp

#include "zeus/COBBox.hpp"

namespace zeus {

CAABox COBBox::calculateAABox(const CTransform& worldXf) const {
  CAABox ret = CAABox::skInvertedBox;

  CTransform trans = worldXf * transform;
  static const CVector3f basis[8] = {{1.f, 1.f, 1.f},    {1.f, 1.f, -1.f},  {1.f, -1.f, 1.f},  {1.f, -1.f, -1.f},
                                     {-1.f, -1.f, -1.f}, {-1.f, -1.f, 1.f}, {-1.f, 1.f, -1.f}, {-1.f, 1.f, 1.f}};
  CVector3f p = extents * basis[0];
  ret.accumulateBounds(trans * p);
  p = extents * basis[1];
  ret.accumulateBounds(trans * p);
  p = extents * basis[2];
  ret.accumulateBounds(trans * p);
  p = extents * basis[3];
  ret.accumulateBounds(trans * p);
  p = extents * basis[4];
  ret.accumulateBounds(trans * p);
  p = extents * basis[5];
  ret.accumulateBounds(trans * p);
  p = extents * basis[6];
  ret.accumulateBounds(trans * p);
  p = extents * basis[7];
  ret.accumulateBounds(trans * p);

  return ret;
}

bool COBBox::OBBIntersectsBox(const COBBox& other) const {
  CVector3f v = other.transform.origin - transform.origin;
  CVector3f T = CVector3f(v.dot(transform.basis[0]), v.dot(transform.basis[1]), v.dot(transform.basis[2]));

  CMatrix3f R;

  float ra, rb, t;

  for (int i = 0; i < 3; ++i)
    for (int k = 0; k < 3; ++k)
      R[i][k] = transform.basis[i].dot(other.transform.basis[k]);

  for (int i = 0; i < 3; ++i) {
    ra = extents[i];
    rb = (other.extents[0] * std::fabs(R[i][0])) + (other.extents[1] * std::fabs(R[i][1])) +
         (other.extents[2] * std::fabs(R[i][2]));
    t = std::fabs(T[i]);

    if (t > (ra + rb + FLT_EPSILON))
      return false;
  }

  for (int k = 0; k < 3; ++k) {
    ra = (extents[0] * std::fabs(R[0][k])) + (extents[1] * std::fabs(R[1][k])) + (extents[2] * std::fabs(R[2][k]));
    rb = other.extents[k];

    t = std::fabs(T[0] * R[0][k] + T[1] * R[1][k] + T[2] * R[2][k]);

    if (t > (ra + rb + FLT_EPSILON))
      return false;
  }

  /* A0 x B0 */
  ra = (extents[1] * std::fabs(R[2][0])) + (extents[2] * std::fabs(R[1][0]));
  rb = (other.extents[1] * std::fabs(R[0][2])) + (other.extents[2] * std::fabs(R[0][1]));
  t = std::fabs((T[2] * R[1][0]) - (T[1] * R[2][0]));
  if (t > (ra + rb + FLT_EPSILON))
    return false;

  /* A0 x B1 */
  ra = (extents[1] * std::fabs(R[2][1])) + (extents[2] * std::fabs(R[1][1]));
  rb = (other.extents[0] * std::fabs(R[0][2])) + (other.extents[2] * std::fabs(R[0][0]));
  t = std::fabs((T[2] * R[1][1]) - (T[1] * R[2][1]));
  if (t > (ra + rb + FLT_EPSILON))
    return false;

  /* A0 x B2 */
  ra = (extents[1] * std::fabs(R[2][2])) + (extents[2] * std::fabs(R[1][2]));
  rb = (other.extents[0] * std::fabs(R[0][1])) + (other.extents[1] * std::fabs(R[0][0]));
  t = std::fabs((T[2] * R[1][2]) - (T[1] * R[2][2]));
  if (t > (ra + rb + FLT_EPSILON))
    return false;

  /* A1 x B0 */
  ra = (extents[0] * std::fabs(R[2][0])) + (extents[2] * std::fabs(R[0][0]));
  rb = (other.extents[1] * std::fabs(R[1][2])) + (other.extents[2] * std::fabs(R[1][1]));
  t = std::fabs((T[0] * R[2][0]) - (T[2] * R[0][0]));
  if (t > (ra + rb + FLT_EPSILON))
    return false;

  /* A1 x B1 */
  ra = (extents[0] * std::fabs(R[2][1])) + (extents[2] * std::fabs(R[0][1]));
  rb = (other.extents[0] * std::fabs(R[1][2])) + (other.extents[2] * std::fabs(R[1][0]));
  t = std::fabs((T[0] * R[2][1]) - (T[2] * R[0][1]));
  if (t > (ra + rb + FLT_EPSILON))
    return false;

  /* A1 x B2 */
  ra = (extents[0] * std::fabs(R[2][2])) + (extents[2] * std::fabs(R[0][2]));
  rb = (other.extents[0] * std::fabs(R[1][1])) + (other.extents[1] * std::fabs(R[1][0]));
  t = std::fabs((T[0] * R[2][2]) - (T[2] * R[0][2]));
  if (t > (ra + rb + FLT_EPSILON))
    return false;

  /* A2 x B0 */
  ra = (extents[0] * std::fabs(R[1][0])) + (extents[1] * std::fabs(R[0][0]));
  rb = (other.extents[1] * std::fabs(R[2][2])) + (other.extents[2] * std::fabs(R[2][1]));
  t = std::fabs((T[1] * R[0][0]) - (T[0] * R[1][0]));
  if (t > (ra + rb + FLT_EPSILON))
    return false;

  /* A2 x B1 */
  ra = (extents[0] * std::fabs(R[1][1])) + (extents[1] * std::fabs(R[0][1]));
  rb = (other.extents[0] * std::fabs(R[2][2])) + (other.extents[2] * std::fabs(R[2][0]));
  t = std::fabs((T[1] * R[0][1]) - (T[0] * R[1][1]));
  if (t > (ra + rb + FLT_EPSILON))
    return false;

  /* A2 x B2 */
  ra = (extents[0] * std::fabs(R[1][2])) + (extents[1] * std::fabs(R[0][2]));
  rb = (other.extents[0] * std::fabs(R[2][1])) + (other.extents[1] * std::fabs(R[2][0]));
  t = std::fabs((T[1] * R[0][2]) - (T[0] * R[1][2]));
  if (t > (ra + rb + FLT_EPSILON))
    return false;

  return true;
}

} // namespace zeus