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/*
* Copyright (C) 2003, 2004 Jason Bevins (original libnoise code)
* Copyright 2010 Thomas J. Hodge (java port of libnoise)
*
* This file is part of libnoiseforjava.
*
* libnoiseforjava is a Java port of the C++ library libnoise, which may be found at
* http://libnoise.sourceforge.net/. libnoise was developed by Jason Bevins, who may be
* contacted at jlbezigvins@gmzigail.com (for great email, take off every 'zig').
* Porting to Java was done by Thomas Hodge, who may be contacted at
* libnoisezagforjava@gzagmail.com (remove every 'zag').
*
* libnoiseforjava 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.
*
* libnoiseforjava 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
* libnoiseforjava. If not, see <http://www.gnu.org/licenses/>.
*
*/
package libnoiseforjava;
public class Interp
{
/// Performs cubic interpolation between two values bound between two other
/// values.
///
/// @param n0 The value before the first value.
/// @param n1 The first value.
/// @param n2 The second value.
/// @param n3 The value after the second value.
/// @param a The alpha value.
///
/// @returns The interpolated value.
///
/// The alpha value should range from 0.0 to 1.0. If the alpha value is
/// 0.0, this function returns @a n1. If the alpha value is 1.0, this
/// function returns @a n2.
public static double cubicInterp (double n0, double n1, double n2, double n3,
double a)
{
double p = (n3 - n2) - (n0 - n1);
double q = (n0 - n1) - p;
double r = n2 - n0;
double s = n1;
return p * a * a * a + q * a * a + r * a + s;
}
/// Performs linear interpolation between two values.
///
/// @param n0 The first value.
/// @param n1 The second value.
/// @param a The alpha value.
///
/// @returns The interpolated value.
///
/// The alpha value should range from 0.0 to 1.0. If the alpha value is
/// 0.0, this function returns @a n0. If the alpha value is 1.0, this
/// function returns @a n1.
public static double linearInterp (double n0, double n1, double a)
{
return ((1.0 - a) * n0) + (a * n1);
}
/// Maps a value onto a cubic S-curve.
///
/// @param a The value to map onto a cubic S-curve.
///
/// @returns The mapped value.
///
/// @a a should range from 0.0 to 1.0.
///
/// The derivative of a cubic S-curve is zero at @a a = 0.0 and @a a =
/// 1.0
public static double SCurve3 (double a)
{
return (a * a * (3.0 - 2.0 * a));
}
/// Maps a value onto a quintic S-curve.
///
/// @param a The value to map onto a quintic S-curve.
///
/// @returns The mapped value.
///
/// @a a should range from 0.0 to 1.0.
///
/// The first derivative of a quintic S-curve is zero at @a a = 0.0 and
/// @a a = 1.0
///
/// The second derivative of a quintic S-curve is zero at @a a = 0.0 and
/// @a a = 1.0
static double SCurve5 (double a)
{
double a3 = a * a * a;
double a4 = a3 * a;
double a5 = a4 * a;
return (6.0 * a5) - (15.0 * a4) + (10.0 * a3);
}
}
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