--- /dev/null
+/*
+ * 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);
+}