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/*
* Copyright (C) 1998, 2000-2007, 2010, 2011, 2012, 2013 SINTEF ICT,
* Applied Mathematics, Norway.
*
* Contact information: E-mail: tor.dokken@sintef.no
* SINTEF ICT, Department of Applied Mathematics,
* P.O. Box 124 Blindern,
* 0314 Oslo, Norway.
*
* This file is part of SISL.
*
* SISL is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as
* published by the Free Software Foundation, either version 3 of the
* License, or (at your option) any later version.
*
* SISL 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 Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public
* License along with SISL. If not, see
* <http://www.gnu.org/licenses/>.
*
* In accordance with Section 7(b) of the GNU Affero General Public
* License, a covered work must retain the producer line in every data
* file that is created or manipulated using SISL.
*
* Other Usage
* You can be released from the requirements of the license by purchasing
* a commercial license. Buying such a license is mandatory as soon as you
* develop commercial activities involving the SISL library without
* disclosing the source code of your own applications.
*
* This file may be used in accordance with the terms contained in a
* written agreement between you and SINTEF ICT.
*/
#include "sisl-copyright.h"
/*
*
* $Id: s1903.c,v 1.2 2001-03-19 15:58:55 afr Exp $
*
*/
#define S1903
#include "sislP.h"
#if defined(SISLNEEDPROTOTYPES)
void
s1903 (double epar[], int in, int ik, int cuopen, double *eknots[], int *jstat)
#else
void
s1903 (epar, in, ik, cuopen, eknots, jstat)
double epar[];
int in;
int ik;
int cuopen;
double *eknots[];
int *jstat;
#endif
/*
*********************************************************************
*
*********************************************************************
*
* PURPOSE : To produce the knot vector of a B-spline basis satisfying the
* interpolation requirements reflected in the epar array.
*
* INPUT : epar - Array containing a parametrization of the
* interpolation conditions. Each interpolation
* condition has got a distinct parameter value
* expect form the cases where several conditions
* are conflicting. In that case a multiple parameter
* value indicates the need of a multiple knot. The
* parameter values are sorted in increasing order.
* The dimension of the array is 'in' if the curve is
* open and 'in+1' if it is closed.
* in - Number of interpolation conditions.
* ik - Order of B-spline basis.
* cuopen - Open/closed curve.
*
* OUTPUT : eknots - The produced knot vector. The dimension of
* the array is in+ik if the curve is open.
* If the curve is closed the dimension of the array
* is in+2*ik-1 if the curve is even and in+2*ik if it is
* odd.
* jstat - status messages
*
* METHOD :
*
*
* REFERENCES :
*
*
* CALLS :
*
*
* WRITTEN BY : Vibeke Skytt, SI, 91-03
* REVISED BY : Trond Vidar Stensby, SI, 91-06
*
*********************************************************************
*/
{
int kpos = 0;
int ki; /* Counter used to traverse the knot vector. */
int kpar; /* Counter used to traverse the parametrization
array. */
int kn; /* The number of conditions in epar. (closed) */
int kk2; /* Half the order. */
int kstop; /* Control variable of loop. */
int kmult; /* Multiplisity of knot. */
double tprev; /* Value of previous knot. */
double curr; /* Value of current knot. */
double tval1; /* Start parameter value. */
double tval2; /* End parameter value. */
double tparint; /* The parameter interval. (closed) */
double tdum; /* Help parameter used for parameter interval. */
*jstat = 0;
/* Check if curve is closed or open. */
if (cuopen)
{
/* O P E N C U R V E */
*eknots = newarray (in +ik, DOUBLE);
if (*eknots == SISL_NULL)
goto err101;
kk2 = ik / 2;
tval1 = epar[0];
tval2 = epar[in -1];
/* Store a knot of multiplisity equal to the order at the start of the
curve The value of the knot is equal to the value of the start
parameter value. */
for (ki = 0; ki < ik; ki++)
(*eknots)[ki] = tval1;
if (ik % 2 == 0)
{
/* The order is even.
Place the internal knots at the parameter values. */
for (kpar = kk2, kstop = in -kk2; kpar < kstop; kpar++, ki++)
(*eknots)[ki] = epar[kpar];
}
else
{
/* The order is odd.
Place the internal knots between the parameter values. */
for (kpar = kk2, kstop = in -kk2 - 1; kpar < kstop; kpar++, ki++)
(*eknots)[ki] = (double) 0.5 *(epar[kpar] + epar[kpar + 1]);
}
/* Store a knot of multiplisity equal to the order at the end of
the curve. The value of the knot is equal to the value of the
end parameter value. */
for (ki = 0; ki < ik; ki++)
(*eknots)[in +ki] = tval2;
}
else
{
/* C L O S E D C U R V E */
*eknots = newarray (in +2 * ik, DOUBLE);
if (*eknots == SISL_NULL)
goto err101;
kn = in +1;
kk2 = ik / 2;
kstop = in +2 * ik - 1;
tparint = epar[in] -epar[0];
if (ik % 2 == 0)
{
/* The order of the B-spline curve is even.
Make the ik-1 first knots as a shift of the last knots. */
for (ki = 0, kpar = in -ik + 1; ki < ik - 1; ki++, kpar++)
(*eknots)[ki] = epar[kpar] - tparint;
/* Make the knots corresponding to the data points. */
for (kpar = 0; kpar < kn; ki++, kpar++)
(*eknots)[ki] = epar[kpar];
/* Make the ik-1 last knots. */
for (kpar = 1; ki < kstop; ki++, kpar++)
{
tdum = tparint;
/* We may risk that a double cyclic use of the parameter
values may result. */
if (kpar > kn)
{
tdum += tparint;
kpar -= in;
}
(*eknots)[ki] = epar[kpar] + tdum;
}
}
else
{
/* The order of the B-spline curve is odd.
Make the ik-1 first knots. */
for (ki = 0, kpar = in -ik + 1; ki < ik - 1; ki++, kpar++)
(*eknots)[ki] = (double) 0.5 *(epar[kpar] + epar[kpar + 1]) - tparint;
/* Make the in next knots. */
for (kpar = 0; kpar < in; ki++, kpar++)
(*eknots)[ki] = (double) 0.5 *(epar[kpar] + epar[kpar + 1]);
/* Make the ik remaining knots. */
for (kpar = 0; ki < kstop; ki++, kpar++)
{
tdum = tparint;
/* We may risk that a double cyclic use of the parameter
values may result. */
if (kpar > kn)
{
tdum += tparint;
kpar -= in;
}
(*eknots)[ki] = (double) 0.5 *(epar[kpar] + epar[kpar + 1]) + tdum;
}
}
}
/* Check that the produced knots are in increasing order and that
the multiplicity is not greater than ik. */
if (cuopen)
kstop = in +ik;
for (ki = 1, tprev = (*eknots)[0], kmult = 0; ki < kstop; ki++, tprev = curr)
{
curr = (*eknots)[ki];
kmult++;
if (tprev > curr)
goto err112; /* Decreasing parameter value. */
if (tprev < curr)
kmult = 1;
if (kmult > ik)
goto err112; /* Knot multiplisity greater than order. */
}
/* The knot vector is produced. */
goto out;
/* Error in scratch allocation. */
err101:
*jstat = -101;
s6err ("s1903", *jstat, kpos);
goto out;
/* Error in the knot vector. */
err112:
*jstat = -112;
s6err ("s1903", *jstat, kpos);
goto out;
out:
return;
}
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