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/*
* The 3D Studio File Format Library
* Copyright (C) 1996-2001 by J.E. Hoffmann <je-h@gmx.net>
* All rights reserved.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 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 Lesser General Public
* License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program; if not, write to the Free Software Foundation,
* Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
* $Id: ease.c,v 1.4 2001/01/12 10:29:17 jeh Exp $
*/
#define LIB3DS_EXPORT
#include <lib3ds/ease.h>
/*!
* \defgroup ease Ease
*
* \author J.E. Hoffmann <je-h@gmx.net>
*/
/*!
* \ingroup ease
*/
Lib3dsFloat
lib3ds_ease(Lib3dsFloat fp, Lib3dsFloat fc, Lib3dsFloat fn,
Lib3dsFloat ease_from, Lib3dsFloat ease_to)
{
Lib3dsDouble s,step;
Lib3dsDouble tofrom;
Lib3dsDouble a;
s=step=(Lib3dsFloat)(fc-fp)/(fn-fp);
tofrom=ease_to+ease_from;
if (tofrom!=0.0) {
if (tofrom>1.0) {
ease_to=(Lib3dsFloat)(ease_to/tofrom);
ease_from=(Lib3dsFloat)(ease_from/tofrom);
}
a=1.0/(2.0-(ease_to+ease_from));
if (step<ease_from) s=a/ease_from*step*step;
else {
if ((1.0-ease_to)<=step) {
step=1.0-step;
s=1.0-a/ease_to*step*step;
}
else {
s=((2.0*step)-ease_from)*a;
}
}
}
return((Lib3dsFloat)s);
}
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