/********************************************************/
/* Code for testing if a Cube intersects with a triangle, from: */
/* http://fileadmin.cs.lth.se/cs/Personal/Tomas_Akenine-Moller/code/tribox3.txt*/

/* AABB-triangle overlap test code                      */

/* by Tomas Akenine-Möller                              */

/* Function: int triBoxOverlap(float boxcenter[3],      */

/*          float boxhalfsize[3],float triverts[3][3]); */

/* History:                                             */

/*   2001-03-05: released the code in its first version */

/*   2001-06-18: changed the order of the tests, faster */

/*                                                      */

/* Acknowledgement: Many thanks to Pierre Terdiman for  */

/* suggestions and discussions on how to optimize code. */

/* Thanks to David Hunt for finding a ">="-bug!         */

/********************************************************/

#include <math.h>

#include <stdio.h>



#define X 0

#define Y 1

#define Z 2



#define CROSS(dest,v1,v2) dest[0]=v1[1]*v2[2]-v1[2]*v2[1]; dest[1]=v1[2]*v2[0]-v1[0]*v2[2]; dest[2]=v1[0]*v2[1]-v1[1]*v2[0];



#define DOT(v1,v2) (v1[0]*v2[0]+v1[1]*v2[1]+v1[2]*v2[2])



#define SUB(dest,v1,v2) dest[0]=v1[0]-v2[0]; dest[1]=v1[1]-v2[1]; dest[2]=v1[2]-v2[2]; 



#define FINDMINMAX(x0,x1,x2,min,max) min = max = x0; if(x1<min) min=x1; if(x1>max) max=x1; if(x2<min) min=x2; if(x2>max) max=x2;



int planeBoxOverlap(float normal[3], float vert[3], float maxbox[3])	// -NJMP-

{

  int q;

  float vmin[3],vmax[3],v;

  for(q=X;q<=Z;q++)

  {

    v=vert[q];					// -NJMP-

    if(normal[q]>0.0f)

    {

      vmin[q]=-maxbox[q] - v;	// -NJMP-

      vmax[q]= maxbox[q] - v;	// -NJMP-

    }

    else

    {

      vmin[q]= maxbox[q] - v;	// -NJMP-

      vmax[q]=-maxbox[q] - v;	// -NJMP-

    }

  }

  if(DOT(normal,vmin)>0.0f) return 0;	// -NJMP-

  if(DOT(normal,vmax)>=0.0f) return 1;	// -NJMP-

  

  return 0;

}





/*======================== X-tests ========================*/

#define AXISTEST_X01(a, b, fa, fb)	p0 = a*v0[Y] - b*v0[Z]; p2 = a*v2[Y] - b*v2[Z]; if(p0<p2) {min=p0; max=p2;} else {min=p2; max=p0;} 	rad = fa * boxhalfsize[Y] + fb * boxhalfsize[Z];   if(min>rad || max<-rad) return 0;



#define AXISTEST_X2(a, b, fa, fb) p0 = a*v0[Y] - b*v0[Z]; p1 = a*v1[Y] - b*v1[Z]; if(p0<p1) {min=p0; max=p1;} else {min=p1; max=p0;} rad = fa * boxhalfsize[Y] + fb * boxhalfsize[Z];   if(min>rad || max<-rad) return 0;



/*======================== Y-tests ========================*/

#define AXISTEST_Y02(a, b, fa, fb) p0 = -a*v0[X] + b*v0[Z]; p2 = -a*v2[X] + b*v2[Z]; if(p0<p2) {min=p0; max=p2;} else {min=p2; max=p0;}  rad = fa * boxhalfsize[X] + fb * boxhalfsize[Z]; if(min>rad || max<-rad) return 0;



#define AXISTEST_Y1(a, b, fa, fb) p0 = -a*v0[X] + b*v0[Z]; p1 = -a*v1[X] + b*v1[Z]; if(p0<p1) {min=p0; max=p1;} else {min=p1; max=p0;} rad = fa * boxhalfsize[X] + fb * boxhalfsize[Z]; if(min>rad || max<-rad) return 0;



/*======================== Z-tests ========================*/



#define AXISTEST_Z12(a, b, fa, fb) p1 = a*v1[X] - b*v1[Y]; p2 = a*v2[X] - b*v2[Y]; if(p2<p1) {min=p2; max=p1;} else {min=p1; max=p2;} rad = fa * boxhalfsize[X] + fb * boxhalfsize[Y]; if(min>rad || max<-rad) return 0;



#define AXISTEST_Z0(a, b, fa, fb) p0 = a*v0[X] - b*v0[Y]; p1 = a*v1[X] - b*v1[Y]; if(p0<p1) {min=p0; max=p1;} else {min=p1; max=p0;}  rad = fa * boxhalfsize[X] + fb * boxhalfsize[Y]; if(min>rad || max<-rad) return 0;



int triBoxOverlap(float bc0, float bc1, float bc2, float bhs0, float bhs1, float bhs2, float tv0, float tv1, float tv2, float tv3, float tv4, float tv5, float tv6, float tv7, float tv8)

{
   
   float boxcenter[3] = {bc0, bc1, bc2};
   
   float boxhalfsize[3] = {bhs0, bhs1, bhs2};
   
   float triverts[3][3] = {tv0, tv1, tv2, tv3, tv4, tv5, tv6, tv7, tv8};


  /*    use separating axis theorem to test overlap between triangle and box */

  /*    need to test for overlap in these directions: */

  /*    1) the {x,y,z}-directions (actually, since we use the AABB of the triangle */

  /*       we do not even need to test these) */

  /*    2) normal of the triangle */

  /*    3) crossproduct(edge from tri, {x,y,z}-directin) */

  /*       this gives 3x3=9 more tests */

   float v0[3],v1[3],v2[3];

//   float axis[3];

   float min,max,p0,p1,p2,rad,fex,fey,fez;		// -NJMP- "d" local variable removed

   float normal[3],e0[3],e1[3],e2[3];



   /* This is the fastest branch on Sun */

   /* move everything so that the boxcenter is in (0,0,0) */

   SUB(v0,triverts[0],boxcenter);

   SUB(v1,triverts[1],boxcenter);

   SUB(v2,triverts[2],boxcenter);



   /* compute triangle edges */

   SUB(e0,v1,v0);      /* tri edge 0 */

   SUB(e1,v2,v1);      /* tri edge 1 */

   SUB(e2,v0,v2);      /* tri edge 2 */



   /* Bullet 3:  */

   /*  test the 9 tests first (this was faster) */

   fex = fabsf(e0[X]);

   fey = fabsf(e0[Y]);

   fez = fabsf(e0[Z]);

   AXISTEST_X01(e0[Z], e0[Y], fez, fey);

   AXISTEST_Y02(e0[Z], e0[X], fez, fex);

   AXISTEST_Z12(e0[Y], e0[X], fey, fex);



   fex = fabsf(e1[X]);

   fey = fabsf(e1[Y]);

   fez = fabsf(e1[Z]);

   AXISTEST_X01(e1[Z], e1[Y], fez, fey);

   AXISTEST_Y02(e1[Z], e1[X], fez, fex);

   AXISTEST_Z0(e1[Y], e1[X], fey, fex);



   fex = fabsf(e2[X]);

   fey = fabsf(e2[Y]);

   fez = fabsf(e2[Z]);

   AXISTEST_X2(e2[Z], e2[Y], fez, fey);

   AXISTEST_Y1(e2[Z], e2[X], fez, fex);

   AXISTEST_Z12(e2[Y], e2[X], fey, fex);



   /* Bullet 1: */

   /*  first test overlap in the {x,y,z}-directions */

   /*  find min, max of the triangle each direction, and test for overlap in */

   /*  that direction -- this is equivalent to testing a minimal AABB around */

   /*  the triangle against the AABB */



   /* test in X-direction */

   FINDMINMAX(v0[X],v1[X],v2[X],min,max);

   if(min>boxhalfsize[X] || max<-boxhalfsize[X]) return 0;



   /* test in Y-direction */

   FINDMINMAX(v0[Y],v1[Y],v2[Y],min,max);

   if(min>boxhalfsize[Y] || max<-boxhalfsize[Y]) return 0;



   /* test in Z-direction */

   FINDMINMAX(v0[Z],v1[Z],v2[Z],min,max);

   if(min>boxhalfsize[Z] || max<-boxhalfsize[Z]) return 0;



   /* Bullet 2: */

   /*  test if the box intersects the plane of the triangle */

   /*  compute plane equation of triangle: normal*x+d=0 */

   CROSS(normal,e0,e1);

   // -NJMP- (line removed here)

   if(!planeBoxOverlap(normal,v0,boxhalfsize)) return 0;	// -NJMP-



   return 1;   /* box and triangle overlaps */

}