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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: s6crvature.c,v 1.1 1994-04-21 12:10:42 boh Exp $
*
*/
#define S6CURVATURE
#include "sislP.h"
#if defined(SISLNEEDPROTOTYPES)
void
s6curvature(double eder[],int idim,double ecurv[],int *jstat)
#else
void s6curvature(eder,idim,ecurv,jstat)
int idim,*jstat;
double eder[],ecurv[];
#endif
/*
*********************************************************************
*
* PURPOSE : Given position, first and second derivative of a curve at
* a point, compute curvature vector.
*
*
*
* INPUT : eder - Array containing position, 1. and 2. derivative of
* curve. Dimension is 3*idim.
* idim - Dimension of geometry space.
*
*
* OUTPUT : ecurv - Curvature vector.
* jstat - status messages
* = 1 : Tangent vector zero.
* = 0 : ok
* < 0 : error
*
*
* METHOD : Express the curve using cord length parametrisation. Then the
* curvature is equal to the 2. derivative of the curve.
*
* REFERENCES :
*
* USE :
*
*-
* CALLS : s6length - Length of vector.
* s6scpr - Scalar product between two vectors.
*
* WRITTEN BY : Vibeke Skytt, SI, 04.90.
*
*********************************************************************
*/
{
int kstat = 0; /* Status variable. */
int ki; /* Counter. */
double tleng; /* Length of first derivative. */
double tleng2; /* Square of length. */
double tdot; /* Scalar product between 1. and 2. derivative. */
/* Compute length of 1. derivative. */
tleng = s6length(eder+idim,idim,&kstat);
if (kstat == 0)
{
/* The first derivative is zero. */
for (ki=0; ki<idim; ki++) ecurv[ki] = (double)0.0;
goto warn1;
}
else
{
tleng2 = tleng*tleng;
tdot = s6scpr(eder+idim,eder+2*idim,idim);
for (ki=0; ki<idim; ki++)
ecurv[ki] = (eder[2*idim+ki] - eder[idim*ki]*tdot/tleng2)/tleng2;
}
*jstat = 0;
goto out;
warn1 :
*jstat = 1;
goto out;
out :
return;
}
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