// Example of tetrahedron volumes to get relative rotation WRT a segment

int xCoord[5],yCoord[5],zCoord[5];

/*---------------------------------------------------------------------
O'Rourke
---------------------------------------------------------------------*/
double  Volumei(int a, int b, int c, int p)
{
   double     vol;
   double  ax, ay, az, bx, by, bz, cx, cy, cz;

   ax = xCoord[a] - xCoord[p];
   ay = yCoord[a] - yCoord[p];
   az = zCoord[a] - zCoord[p];
   bx = xCoord[b] - xCoord[p];
   by = yCoord[b] - yCoord[p];
   bz = zCoord[b] - zCoord[p];
   cx = xCoord[c] - xCoord[p];
   cy = yCoord[c] - yCoord[p];
   cz = zCoord[c] - zCoord[p];

   vol =   ax * (by*cz - bz*cy)
         + ay * (bz*cx - bx*cz)
         + az * (bx*cy - by*cx);

   return vol;
}

main()
{
int a=0,b=1,c=2,d=3,cPrime=4;

xCoord[a]=50;
yCoord[a]=50;
zCoord[a]=50;

xCoord[b]=50;
yCoord[b]=20;
zCoord[b]=50;

//xCoord[c]=80;
xCoord[c]=150;
yCoord[c]=35;
zCoord[c]=80;

xCoord[d]=70;
yCoord[d]=40;
zCoord[d]=40;

xCoord[cPrime]=80;
yCoord[cPrime]=25;
zCoord[cPrime]=60;

printf("Volumei(a,b,c,d)=%f\n\n",Volumei(a,b,c,d));

printf("Volumei(a,b,cPrime,d)=%f\n\n",Volumei(a,b,cPrime,d));

printf("Volumei(a,b,c,cPrime)=%f\n\n",Volumei(a,b,c,cPrime));
}