66 lines
1.7 KiB
C++
66 lines
1.7 KiB
C++
/*
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* The 3D Studio File Format Library
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* Copyright (C) 1996-2001 by J.E. Hoffmann <je-h@gmx.net>
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* All rights reserved.
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation; either version 2.1 of the License, or (at
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* your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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* License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this program; if not, write to the Free Software Foundation,
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* Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*
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* $Id$
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*/
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#define LIB3DS_EXPORT
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#include "ease.h"
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/*!
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* \defgroup ease Ease
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*
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* \author J.E. Hoffmann <je-h@gmx.net>
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*/
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/*!
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* \ingroup ease
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*/
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Lib3dsFloat
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lib3ds_ease(Lib3dsFloat fp, Lib3dsFloat fc, Lib3dsFloat fn,
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Lib3dsFloat ease_from, Lib3dsFloat ease_to)
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{
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Lib3dsDouble s,step;
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Lib3dsDouble tofrom;
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Lib3dsDouble a;
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s=step=(Lib3dsFloat)(fc-fp)/(fn-fp);
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tofrom=ease_to+ease_from;
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if (tofrom!=0.0) {
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if (tofrom>1.0) {
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ease_to=(Lib3dsFloat)(ease_to/tofrom);
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ease_from=(Lib3dsFloat)(ease_from/tofrom);
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}
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a=1.0/(2.0-(ease_to+ease_from));
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if (step<ease_from) s=a/ease_from*step*step;
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else {
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if ((1.0-ease_to)<=step) {
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step=1.0-step;
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s=1.0-a/ease_to*step*step;
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}
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else {
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s=((2.0*step)-ease_from)*a;
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}
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}
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}
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return((Lib3dsFloat)s);
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}
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