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// This file contains the definition for class RayIntersectionInfo.

#include "core/cross/precompile.h"
#include "core/cross/ray_intersection_info.h"

namespace o3d {

static const float kEpsilon = 0.000001;

// TODO: Someone who is better at math, please optimize this.
bool RayIntersectionInfo::IntersectTriangle(const Point3& start,
                                            const Point3& end,
                                            const Point3& vert0,
                                            const Point3& vert1,
                                            const Point3& vert2,
                                            Point3* intersectionPoint) {
  Vector3 ab(vert1 - vert0);
  Vector3 ac(vert2 - vert0);
  Vector3 qp(start - end);

  Vector3 n(cross(ab, ac));

  float d = dot(qp, n);
  if (d <= 0.0f) {
    return false;
  }

  Vector3 ap(start - vert0);
  float t = dot(ap, n);
  if (t < 0.0f) {
    return false;
  }
  if (t > d) {
    return false;
  }

  Vector3 e(cross(qp, ap));
  float v = dot(ac, e);
  if (v < 0.0f || v > d) {
    return false;
  }

  float w = -dot(ab, e);
  if (w < 0.0f || v + w > d) {
    return false;
  }

  float ood = 1.0f / d;
  t *= ood;
  v *= ood;
  w *= ood;
  float u = 1.0f - v -w;

  *intersectionPoint = Point3(
      Vector3(vert0) * u + Vector3(vert1) * v + Vector3(vert2) * w);

  return true;
}

}  // namespace o3d