libcruft-util/noise/basis/worley.ipp

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/*
* 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_WORLEY_IPP
#error
#endif
#define __UTIL_NOISE_BASIS_WORLEY_IPP
#include "../../debug.hpp"
#include "../../hash/murmur/murmur2.hpp"
namespace util { namespace noise { namespace basis {
///////////////////////////////////////////////////////////////////////////
template <typename T, size_t F>
worley<T,F>::worley (seed_t _seed):
seed (_seed)
{ ; }
//-------------------------------------------------------------------------
template <typename T, size_t F>
worley<T,F>::worley ():
worley (time (nullptr))
{ ; }
//-------------------------------------------------------------------------
template <typename T, size_t F>
util::range<T>
worley<T,F>::bounds (void) const
{
return { 0.0, 1.5 };
}
//-------------------------------------------------------------------------
template <typename T, size_t F>
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constexpr T
worley<T,F>::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).template as<point> ();
// setup an array of distances
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constexpr size_t RADIUS = 1;
constexpr size_t COUNT = pow2 (RADIUS * 2 + 1);
T distances[COUNT] = { std::numeric_limits<T>::quiet_NaN () };
T *cursor = distances;
// record the distances to each candidate point
for (signed y_off = -signed(RADIUS); y_off <= signed(RADIUS) ; ++y_off) {
for (signed x_off = -signed(RADIUS); x_off <= signed(RADIUS); ++x_off) {
auto off = vector<2,intmax_t> {x_off, y_off};
auto pos = generate (p_int + off);
CHECK_LIMIT (pos.x, T{0}, T{1});
CHECK_LIMIT (pos.y, T{0}, T{1});
*cursor = distance2 (pos + off, p_rem);
cursor++;
}
}
// find the f'th lowest value
static_assert (F < COUNT, "worley order must be less than search radius");
std::partial_sort (distances, distances + F, distances + COUNT);
CHECK_GE (distances[F], 0);
return distances[F];
}
//////////////////////////////////////////////////////////////////////////
template <typename T, size_t F>
constexpr point<2,T>
worley<T,F>::generate (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::point<2,T> {
(u & 0xffff) / T{0xffff},
(v & 0xffff) / T{0xffff}
};
CHECK_LIMIT (r, T{0}, T{1});
return r;
}
} } }