/usr/include/libnoise/interp.h is in libnoise-dev 1.0.0+repack-1.
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//
// Copyright (C) 2003, 2004 Jason Bevins
//
// This library 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 library 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 (COPYING.txt) for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with this library; if not, write to the Free Software Foundation,
// Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
//
// The developer's email is jlbezigvins@gmzigail.com (for great email, take
// off every 'zig'.)
//
#ifndef NOISE_INTERP_H
#define NOISE_INTERP_H
namespace noise
{
/// @addtogroup libnoise
/// @{
/// 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.
inline 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.
inline 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 derivitive of a cubic S-curve is zero at @a a = 0.0 and @a a =
/// 1.0
inline 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 derivitive of a quintic S-curve is zero at @a a = 0.0 and
/// @a a = 1.0
///
/// The second derivitive of a quintic S-curve is zero at @a a = 0.0 and
/// @a a = 1.0
inline 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);
}
// @}
}
#endif
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