libcruft-util/noise/fractal/hmf.ipp

67 lines
1.8 KiB
C++

/*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* Copyright 2012-2015 Danny Robson <danny@nerdcruft.net>
*/
#ifdef __UTIL_NOISE_FRACTAL_HMF_IPP
#error
#endif
#define __UTIL_NOISE_FRACTAL_HMF_IPP
namespace util { namespace noise { namespace fractal {
//-------------------------------------------------------------------------
// H should be fairly low due to the decreasing weight parameter in eval
template <typename T, typename B>
hmf<T,B>::hmf ():
H (0.25f),
octaves (6),
frequency (0.1f),
lacunarity (2),
offset (0.7f),
amplitude (1),
gain (1 / lacunarity),
invAH (std::pow (amplitude, -H)),
invGH (std::pow (gain, H))
{ ; }
//-------------------------------------------------------------------------
template <typename T, typename B>
constexpr T
hmf<T,B>::operator() (util::point<2,T> p) const
{
T scale = invAH;
T result = 0;
T signal = 0;
T weight = 1;
p *= frequency;
for (size_t i = 0; i < octaves; ++i) {
signal = (basis (p) + offset) * scale;
result += signal * weight;
weight *= signal;
weight = min (weight, T{1});
scale *= invGH;
p *= lacunarity;
}
return result;
}
} } }