libcruft-util/noise/basis/perlin.cpp

119 lines
3.7 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>
*/
#include "perlin.hpp"
#include "../../hash/murmur/murmur2.hpp"
using util::noise::basis::perlin;
///////////////////////////////////////////////////////////////////////////////
template <typename T>
util::vector<2,T>
generate (util::point<2,T> p, uint64_t seed)
{
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;
}
///////////////////////////////////////////////////////////////////////////////
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>
T
perlin<T,L>::operator() (util::point<2,T> p) const
{
auto p_int = p.template cast<intmax_t> ();
auto p_rem = p - p_int;
// Shift the coordinate system down a little to ensure we get unit weights
// for the lerp. It's better to do this than abs the fractional portion so
// we don't get reflections along the origin.
if (p.x < 0) { p_rem.x = 1 + p_rem.x; p_int.x -= 1; }
if (p.y < 0) { p_rem.y = 1 + p_rem.y; p_int.y -= 1; }
// Generate the four corner values. It's not strictly necessary to
// normalise the values, but we get a more consistent and visually
// appealing range of outputs with normalised values.
auto p0 = generate<T> (p_int + util::vector<2,T> { 0, 0 }, this->seed).normalise ();
auto p1 = generate<T> (p_int + util::vector<2,T> { 1, 0 }, this->seed).normalise ();
auto p2 = generate<T> (p_int + util::vector<2,T> { 0, 1 }, this->seed).normalise ();
auto p3 = generate<T> (p_int + util::vector<2,T> { 1, 1 }, this->seed).normalise ();
T v0 = p0.x * p_rem.x + p0.y * p_rem.y;
T v1 = p1.x * (p_rem.x - 1) + p1.y * p_rem.y;
T v2 = p2.x * p_rem.x + p2.y * (p_rem.y - 1);
T v3 = p3.x * (p_rem.x - 1) + p3.y * (p_rem.y - 1);
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_;
}
///////////////////////////////////////////////////////////////////////////////
#include "../lerp.hpp"
namespace util { namespace noise { namespace basis {
template struct perlin<float, lerp::linear>;
template struct perlin<float, lerp::cubic>;
template struct perlin<float, lerp::quintic>;
template struct perlin<double, lerp::linear>;
template struct perlin<double, lerp::cubic>;
template struct perlin<double, lerp::quintic>;
} } }