libcruft-util/noise/basis/perlin.ipp

110 lines
3.3 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_BASIS_PERLIN_IPP
#error
#endif
#define __UTIL_NOISE_BASIS_PERLIN_IPP
#include "../../hash/murmur/murmur2.hpp"
namespace util { namespace noise { namespace basis {
///////////////////////////////////////////////////////////////////////////
template <typename T, util::noise::lerp_t<T> L>
perlin<T,L>::perlin (seed_t _seed):
seed (_seed)
{ ; }
//-------------------------------------------------------------------------
template <typename T, util::noise::lerp_t<T> L>
perlin<T,L>::perlin ():
seed (time (nullptr))
{ ; }
//-------------------------------------------------------------------------
template <typename T, util::noise::lerp_t<T> L>
util::range<T>
perlin<T,L>::bounds (void) const
{
return {
-std::sqrt (T{2}) / 2,
std::sqrt (T{2}) / 2
};
}
//-------------------------------------------------------------------------
template <typename T, util::noise::lerp_t<T> L>
constexpr T
perlin<T,L>::operator() (util::point<2,T> p) const
{
// extract integer and fractional parts. be careful to always round down
// (particularly with negatives) and avoid rounding errors.
auto p_int = p.template cast<intmax_t> ();
if (p.x < 0) p_int.x -= 1;
if (p.y < 0) p_int.y -= 1;
auto p_rem = abs (p - p_int);
// generate the corner positions
auto p0 = p_int + util::vector<2,intmax_t> { 0, 0 };
auto p1 = p_int + util::vector<2,intmax_t> { 1, 0 };
auto p2 = p_int + util::vector<2,intmax_t> { 0, 1 };
auto p3 = p_int + util::vector<2,intmax_t> { 1, 1 };
// generate the corner gradients
auto g0 = gradient (p0);
auto g1 = gradient (p1);
auto g2 = gradient (p2);
auto g3 = gradient (p3);
// compute the dot products
T v0 = dot (g0, p - p0);
T v1 = dot (g1, p - p1);
T v2 = dot (g2, p - p2);
T v3 = dot (g3, p - p3);
// interpolate the results
auto L0 = L (v0, v1, p_rem.x);
auto L1 = L (v2, v3, p_rem.x);
auto L_ = L (L0, L1, p_rem.y);
return L_;
}
///////////////////////////////////////////////////////////////////////////
template <typename T, lerp_t<T> L>
constexpr vector<2,T>
perlin<T,L>::gradient (point<2,intmax_t> p) const
{
using util::hash::murmur2::mix;
auto u = mix (seed, mix (uint64_t (p.x), uint64_t (p.y)));
auto v = mix (u, seed);
auto r = util::vector<2,T> {
(u & 0xffff) / T{0xffff},
(v & 0xffff) / T{0xffff}
} * 2 - 1;
CHECK_GE (r, T{-1});
CHECK_LE (r, T{ 1});
return r;
}
} } }