libcruft-util/lerp.cpp

68 lines
1.7 KiB
C++

/*
* This file is part of libgim.
*
* libgim 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 3 of the License, or (at your option) any later
* version.
*
* libgim 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 libgim. If not, see <http://www.gnu.org/licenses/>.
*
* Copyright 2011 Danny Robson <danny@nerdcruft.net>
*/
#include "lerp.hpp"
#include "debug.hpp"
#include "maths.hpp"
#include <cmath>
double
lerp::sigmoid (double val) {
return -1.0 + 2.0 / (1.0 + exp (-2.0 * val));
}
double lerp::trunc (double a, double, double)
{ return a; }
double
lerp::linear (double a, double b, double weight) {
CHECK (weight >= 0.0 && weight <= 1.0);
return a * (1.0 - weight) + b * weight;
}
double
lerp::cosine (double a, double b, double weight) {
CHECK (weight >= 0.0 && weight <= 1.0);
double t = (1.0 - cos (weight * PI)) * 0.5;
return a * (1.0 - t) + b * t;
}
double
lerp::cubic (double a, double b, double weight) {
CHECK (weight >= 0.0 && weight <= 1.0);
double t = weight * weight * (3.0 - 2.0 * weight);
return a * (1.0 - t) + b * t;
}
double
lerp::quintic (double a, double b, double weight) {
CHECK (weight >= 0.0 && weight <= 1.0);
double t = weight * weight * weight * (weight * (weight * 6.0 - 15.0) + 10.0);
return a * (1.0 - t) + b * t;
}