//===========================================================================
// Copyright (C) 1998, 2000-2007, 2010, 2011, 2012 SINTEF ICT, Applied
// Mathematics, Norway.
//
// This file is part of GoTools
//
// This program is free software; you can redistribute it and/or          
// modify it under the terms of the GNU General Public License            
// as published by the Free Software Foundation version 2 of the License. 
//
// This program 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 General Public License for more details.                           
//
// You should have received a copy of the GNU General Public License      
// along with this program; if not, see <http://www.gnu.org/licenses>
//
// Contact information: E-mail: tor.dokken@sintef.no                      
// SINTEF ICT, Department of Applied Mathematics,                         
// P.O. Box 124 Blindern,                                                 
// 0314 Oslo, Norway.                                                     
//
// Other licenses are also available for this software, notably licenses
// for:
// - Building commercial software.                                        
// - Building software whose source code you wish to keep private.        
//===========================================================================

#include "sisl-copyright.h"

/*
 *
 * $Id: s1770.c,v 1.2 2001-03-19 15:58:53 afr Exp $
 *
 */
#define S1770

#include "sislP.h"

/*
* Forward declarations.
* ---------------------
*/

#if defined(SISLNEEDPROTOTYPES)
static
void
s1770_s9corr(double [],double,double,double,double,double,double);
static
void
s1770_s9dir(double *,double *,double *,double [],double [],double [],int);
#else
static void s1770_s9corr();
static void s1770_s9dir();
#endif

#if defined(SISLNEEDPROTOTYPES)
void 
s1770(SISLCurve *pcurve1,SISLCurve *pcurve2,double aepsge,
	   double astart1,double astart2,double aend1,double aend2,
	   double anext1,double anext2,double *cpos1,double *cpos2,int *jstat)
#else
void s1770(pcurve1,pcurve2,aepsge,astart1,astart2,
	   aend1,aend2,anext1,anext2,cpos1,cpos2,jstat)
     SISLCurve  *pcurve1;
     SISLCurve  *pcurve2;
     double aepsge;
     double astart1;
     double astart2;
     double aend1;
     double aend2;
     double anext1;
     double anext2;
     double *cpos1;
     double *cpos2;
     int    *jstat;
#endif
/*
*********************************************************************
*
*********************************************************************
*
* PURPOSE    : Newton iteration on the distance function between
*              two curves to find a closest point or an intersection point.
*
*
* INPUT      : pcurve1 - Pointer to the first curve in the intersection.
*              pcurve2 - Pointer to the second curve in the intersection.
*              aepsge  - Geometry resolution.
*              astart1 - Start parameter value of the first curve.
*              astart2 - Start parameter value of the second curve.
*              aend1   - End parameter value of the first curve.
*              aend2   - End parameter value of the second curve.
*              anext1  - Start parameter value of the iteration on
*                        the first curve.
*              anext2  - Start parameter value of the iteration on
*                        the second curve.
*
*
*
* OUTPUT     : cpos1   - Parameter value of of first curve in intersection
*                        point.
*              cpos2   - Parameter value of of second curve in intersection
*                        point.
*              jstat   - status messages  
*                                = 2   : A minimum distanse found.
*                                = 1   : Intersection found.
*                                < 0   : error.
*
*
* METHOD     : Newton iteration in two parameter directions.
*
*
* REFERENCES :
*
*
* WRITTEN BY : Arne Laksaa, SI, Feb 1989
*
*********************************************************************
*/                       
{                        
  int kstat = 0;            /* Local status variable.                      */
  int kpos = 0;             /* Position of error.                          */
  int kleft1=0,kleft2=0;    /* Variables used in the evaluator.            */
  int kder=1;               /* Order of derivatives to be calulated        */
  int kdim;                 /* Dimension of space the curves lie in        */
  int knbit;                /* Number of iterations                        */
  int kdir;                 /* Changing direction.                         */
  double tdelta1,tdelta2;   /* Parameter interval of the curves.           */
  double tdist;             /* Distance between position and origo.        */
  double td[2],t1[2],tdn[2];/* Distances between old and new parameter
			       value in the two parameter directions.      */
  double tprev;             /* Previous difference between the curves.     */
  double *sval1=SISL_NULL;       /* Value ,first and second derivatie on curve 1*/ 
  double *sval2;            /* Value ,first and second derivatie on curve 1*/ 
  double *sdiff;            /* Difference between the curves               */
  
  /* Test input.  */
  
  if (pcurve1->idim != pcurve2->idim) goto err106;
  
  kdim = pcurve1 -> idim;
  if (kdim == 2)
  {
     s1770_2D(pcurve1,pcurve2,aepsge,astart1,astart2,
           aend1,aend2,anext1,anext2,cpos1,cpos2,jstat);
     goto out;
  }
  
  /* Fetch endpoints and the intervals of parameter interval of curves.  */
  
  tdelta1 = pcurve1->et[pcurve1->in] - pcurve1->et[pcurve1->ik - 1];
  tdelta2 = pcurve2->et[pcurve2->in] - pcurve2->et[pcurve2->ik - 1];
  
  /* Allocate local used memory */
  
  sval1 = newarray((2*kder+5)*kdim,double);
  if (sval1 == SISL_NULL) goto err101;
  
  sval2 = sval1 + (kder+2)*kdim;
  sdiff = sval2 + (kder+2)*kdim;
  
  /* Initiate variables.  */
  
  tprev = (double)HUGE;
  
  /* Evaluate 0-1.st derivatives of both curves */
  
  s1221(pcurve1,kder,anext1,&kleft1,sval1,&kstat);
  if (kstat < 0) goto error;
  
  s1221(pcurve2,kder,anext2,&kleft2,sval2,&kstat);
  if (kstat < 0) goto error;
  
  /* Compute the distanse vector and value and the new step. */
  
  s1770_s9dir(&tdist,td,td+1,sdiff,sval1,sval2,kdim);
  
  /* Correct if we are not inside the parameter intervall. */
  
  t1[0] = td[0];
  t1[1] = td[1];
  s1770_s9corr(t1,anext1,anext2,astart1,aend1,astart2,aend2);
  
  /* Iterate to find the intersection point.  */
  
  for (knbit = 0; knbit < 30; knbit++)
    {
      /* Evaluate 0-1.st derivatives of both curves */
      
      s1221(pcurve1,kder,anext1+t1[0],&kleft1,sval1,&kstat);
      if (kstat < 0) goto error;
      
      s1221(pcurve2,kder,anext2+t1[1],&kleft2,sval2,&kstat);
      if (kstat < 0) goto error;
      
      
      /* Compute the distanse vector and value and the new step. */
      
      s1770_s9dir(&tdist,tdn,tdn+1,sdiff,sval1,sval2,kdim);
      
      /* Check if the direction of the step have change. */
      
      kdir = (s6scpr(td,tdn,2) >= DZERO);     /* 0 if changed. */
      
      /* Ordinary converging. */
      
      if (tdist < tprev*(double)0.9 || kdir)
	{
          anext1 += t1[0];
          anext2 += t1[1];
	  
          td[0] = tdn[0];
          td[1] = tdn[1];
	  
	  /* Correct if we are not inside the parameter intervall. */
	  
	  t1[0] = td[0];
	  t1[1] = td[1];
	  s1770_s9corr(t1,anext1,anext2,astart1,aend1,astart2,aend2);
	  
          if ( (fabs(t1[0]/tdelta1) <= REL_COMP_RES) &&
	      (fabs(t1[1]/tdelta2) <= REL_COMP_RES) ) break;
	  
          tprev = tdist;
	}
      
      /* Not converging, corrigate and try again. */
      
      else
	{
          t1[0] /= (double)2;
          t1[1] /= (double)2;
          /* knbit--; */
	}
    }
  
  /* Iteration stopped, test if point founds found is within resolution */
  
  if (tdist <= aepsge)
    *jstat = 1;
  else
    *jstat = 2;
  
  *cpos1 = anext1;
  *cpos2 = anext2;
  
  /* Iteration completed.  */
  
  
  goto out;
  
  /* Error in allocation */
  
 err101: *jstat = -101;
  s6err("s1770",*jstat,kpos);
  goto out;                  
  
  /* Error in input. Conflicting dimensions.  */
  
 err106: *jstat = -106;
  s6err("s1770",*jstat,kpos);
  goto out;                  
  
  /* Error in lower level routine.  */
  
  error : *jstat = kstat;
  s6err("s1770",*jstat,kpos);
  goto out;                  
  
 out:    if (sval1 != SISL_NULL) freearray(sval1);
}

#if defined(SISLNEEDPROTOTYPES)
static
void
s1770_s9corr(double gdn[],double acoef1,double acoef2,
		   double astart1,double aend1,double astart2,double aend2)
#else
static void s1770_s9corr(gdn,acoef1,acoef2,astart1,aend1,astart2,aend2)
     double gdn[];
     double acoef1;
     double acoef2;
     double astart1;
     double aend1;
     double astart2;
     double aend2;
#endif
/*
*********************************************************************
*
*********************************************************************
*                                                                   
* PURPOSE    : To be sure that we are inside the boorder of the
*              parameter plan. If we are outside clipping is used
*	       to corrigate the step value.
*
*
* INPUT      : acoef1  - Coeffisient in the first direction.
*              acoef2  - Coeffisient in the second direction.
*              astart1 - The lower boorder in first direction.
*              aend1   - The higher boorder in first direction.
*              astart2 - The lower boorder in second direction.
*              aend2   - The higher boorder in second direction.
*
*
*
* INPUT/OUTPUT : gdn   - Old and new step value.
*
*
* METHOD     : 
*
*
* REFERENCES :
*
*
* WRITTEN BY : Arne Laksaa, SI, Feb 1989
*
*********************************************************************
*/                       
{
  if (acoef1 + gdn[0] < astart1) 
    gdn[0] = astart1 - acoef1;
  else if (acoef1 + gdn[0] > aend1)   
    gdn[0] = aend1 - acoef1;

  if (acoef2 + gdn[1] < astart2) 
    gdn[1] = astart2 - acoef2;
  else if (acoef2 + gdn[1] > aend2)   
    gdn[1] = aend2 - acoef2;
}

#if defined(SISLNEEDPROTOTYPES)
static
void
s1770_s9dir(double *cdist,double *cdiff1,double *cdiff2,
		  double gdiff[],double eval1[],double eval2[],int idim)
#else
static void s1770_s9dir(cdist,cdiff1,cdiff2,gdiff,eval1,eval2,idim)
     double *cdist;
     double *cdiff1;
     double *cdiff2;
     double eval1[];
     double eval2[];
     double gdiff[];
     int    idim;
#endif
/*
*********************************************************************
*
*********************************************************************
*                                                                   
* PURPOSE    : To compute the distance vector and value beetween
*	       a points on the first curve and a point on the second
*	       curve. And to compute a next step on both curves.
*	       This is equivalent to the nearest way to the
*	       parameter plan in the tangent plan from a point in the
*	       distance surface between two curves.
*
*
* INPUT      : eval1 - Value and derevative in first parameterdirection.
*              eval2 - Value and derevative in second parameterdirection.
*	       idim  - Dimension of space the curves lie in.
*
*
* OUTPUT     : gdiff   - Array to use when computing the differens vector.
*	       cdiff1  - Relative parameter value in intersection 
*                        point in first direction.
*              cdiff2  - Relative parameter value in intersection 
*                        point in second direction.
*              cdist   - The value to the point in the distance surface.
*
*
* METHOD     : The method is to compute the parameter distance to the points
*	       on both tangents which is closest to each other.
*	       The differens vector beetween these points are orthogonal
*	       to both tangents. If the distance vector beetween the two
*	       points on the curve is "diff" and the two derevativ vectors
*	       are "der1" and "der2", and the two wanted parameter distance
*	       are "dt1" and "dt2", then we get the following system of 
*	       equations:
*		 <dt1*der1+dist-dt2*der2,der2> = 0
*		 <dt1*der1+dist-dt2*der2,der1> = 0
*	       This is futher:
*
*		 | -<der1,der2>   <der2,der2> |  | dt1 |   | <dist,der2> |
*		 |                            |  |     | = |             |
*		 | -<der1,der1>   <der1,der2> |  | dt2 |   | <dist,der1> |
*
*	       The solution of this matrix equation is the
*	       following function.
*
*
* REFERENCES :
*
*
* WRITTEN BY : Arne Laksaa, SI, Feb 1989
*
*********************************************************************
*/                       
{                        
  int kstat;		           /* Local status variable. */
  register double tdet;		   /* Determinant */
  register double t1,t2,t3,t4,t5;  /* Variables in equation system */
  
  /* Computing the different vector */
  
  s6diff(eval1,eval2,idim,gdiff);
  
  /* Computing the length of the different vector. */
  
  *cdist = s6length(gdiff,idim,&kstat);
  
  t1 =  s6scpr(eval1+idim,eval1+idim,idim);
  t2 =  s6scpr(eval1+idim,eval2+idim,idim);
  t3 =  s6scpr(eval2+idim,eval2+idim,idim);
  t4 =  s6scpr(gdiff,eval1+idim,idim);
  t5 =  s6scpr(gdiff,eval2+idim,idim);
  
  /* Computing the determinant. */
  
  tdet = t2*t2 - t1*t3;
  
  if (DEQUAL(tdet,DZERO))
    {
      *cdiff1 = DZERO;
      *cdiff2 = DZERO;
    }
  else 
    {
      /* Using Cramer's rule to find the solution of the system. */
      
      *cdiff1 =  (t4*t3 - t5*t2)/tdet;
      *cdiff2 =  (t2*t4 - t1*t5)/tdet;
    }
}
