/*   ColDet - C++ 3D Collision Detection Library
 *   Copyright (C) 2000   Amir Geva
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 * 
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA  02111-1307, USA.
 *
 * Any comments, questions and bug reports send to:
 *   photon@photoneffect.com
 *
 * Or visit the home page: http://photoneffect.com/coldet/
 */
#include "sysdep.h"
#include "mytritri.h"

Vector3D my_tri_tri_intersect(const Triangle& t1, const Triangle& t2)
{
  Plane p1(t1.v1,t1.v2,t1.v3);
  int other_side=0;
  {
    float f1=p1.Classify(t2.v1);
    float f2=p1.Classify(t2.v2);
    float f3=p1.Classify(t2.v3);
    float f12=f1*f2;
    float f23=f2*f3;
    if (f12>0.0f && f23>0.0f) return Vector3D::Zero;
    other_side=(f12<0.0f?(f23<0.0f?1:0):2);
  }
  Plane p2(t2.v1,t2.v2,t2.v3);
  Vector3D n12(p1.normal+p2.normal);
  TriangleDesc td2(t2,p2);
  const Vector3D& a2=td2[other_side+1];
  const Vector3D& b2=td2[other_side];
  const Vector3D& c2=td2[other_side+2];
  float t21=-(p1.d+p2.d+a2*n12)/((b2-a2)*n12);
  TriangleDesc td1(t1,p1);
  Vector3D P21(a2+t21*(b2-a2));
  if (td1.pointInTri(P21)) return P21;
  float t22=-(p1.d+p2.d+c2*n12)/((b2-c2)*n12);
  Vector3D P22(c2+t22*(b2-c2));
  if (td1.pointInTri(P22)) return P22;

  {
    float f1=p2.Classify(t1.v1);
    float f2=p2.Classify(t1.v2);
    float f3=p2.Classify(t1.v3);
    float f12=f1*f2;
    float f23=f2*f3;
    if (f12>0.0f && f23>0.0f) return Vector3D::Zero;
    other_side=(f12<0.0f?(f23<0.0f?1:0):2);
  }
  const Vector3D& a1=td1[other_side+1];
  const Vector3D& b1=td1[other_side];
  const Vector3D& c1=td1[other_side+2];
  float t11=-(p1.d+p2.d+a1*n12)/((b1-a1)*n12);
  Vector3D P11(a1+t11*(b1-a1));
  if (td2.pointInTri(P11)) return P11;
  float t12=-(p1.d+p2.d+c1*n12)/((b1-c1)*n12);
  Vector3D P12(c1+t12*(b1-c1));
  if (td2.pointInTri(P12)) return P12;
  return Vector3D::Zero;
}