SPLINES.C

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/* --
OpenFX version 1.0 - Modelling, Animation and Rendering Package
Copyright (C) 2000 OpenFX Development Team

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; either version 2
of the License, or (at your option) any later version.

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, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

You may contact the OpenFX development team via elecronic mail
at core@openfx.org, or visit our website at http://openfx.org for
further information and support details.
-- */

/* file Splines.c  for inclusion in Path and modeller */

long SplinesP(double k[], double tau){
 return (long)(tau*(tau*(tau*k[3] + k[2]) + k[1]) + k[0]);
}

double SplinesR(double k[], double tau){
 return (double)(tau*(tau*(tau*k[3] + k[2]) + k[1]) + k[0]);
}

void SplinesK(double k[], long vl, long v1, long v2, long vn){
  k[0] = (double)v1;
  k[1] = -0.5*(double)vl+0.5*(double)v2;
  k[2] = (double)vl-2.5*(double)v1+2.0*(double)v2-0.5*(double)vn;
  k[3] = -0.5*(double)vl+1.5*(double)v1-1.5*(double)v2+0.5*(double)vn;
}

void SplinesG(double k[], double xi, double xi1, double xig, double xig1){
  k[0] = xi;
  k[1] = xig;
  k[2] = -3.0*xi+3.0*xi1-2.0*xig-xig1;
  k[3] = 2.0*xi-2.0*xi1+xig+xig1;
}