/*
Copyright (C) 1996-2008 by Jan Eric Kyprianidis
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.
Thisprogram 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, see .
*/
#include "lib3ds_impl.h"
float
lib3ds_math_ease(float fp, float fc, float fn, float ease_from, float ease_to) {
double s, step;
double tofrom;
double a;
s = step = (float)(fc - fp) / (fn - fp);
tofrom = ease_to + ease_from;
if (tofrom != 0.0) {
if (tofrom > 1.0) {
ease_to = (float)(ease_to / tofrom);
ease_from = (float)(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((float)s);
}
void
lib3ds_math_cubic_interp(float *v, float *a, float *p, float *q, float *b, int n, float t) {
float x, y, z, w;
int i;
x = 2 * t * t * t - 3 * t * t + 1;
y = -2 * t * t * t + 3 * t * t;
z = t * t * t - 2 * t * t + t;
w = t * t * t - t * t;
for (i = 0; i < n; ++i) {
v[i] = x * a[i] + y * b[i] + z * p[i] + w * q[i];
}
}