geom/sample: add trivial poisson sample generator

This commit is contained in:
Danny Robson 2018-04-19 13:27:43 +10:00
parent f31a344912
commit 89defb3bc2
3 changed files with 79 additions and 2 deletions

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@ -240,6 +240,7 @@ list (
geom/ray.hpp geom/ray.hpp
geom/rect.cpp geom/rect.cpp
geom/rect.hpp geom/rect.hpp
geom/sample.cpp
geom/sample.hpp geom/sample.hpp
geom/sphere.cpp geom/sphere.cpp
geom/sphere.hpp geom/sphere.hpp

71
geom/sample.cpp Normal file
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@ -0,0 +1,71 @@
/*
* 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 2018 Danny Robson <danny@nerdcruft.net>
*/
#include "sample.hpp"
#include "../point.hpp"
#include <random>
///////////////////////////////////////////////////////////////////////////////
std::vector<util::point2f>
util::geom::poisson_sample (util::extent2i area, float distance, int samples)
{
std::vector<util::point2f> selected;
std::vector<util::point2f> candidates (samples);
std::uniform_real_distribution<float> dist_w (0, area.w);
std::uniform_real_distribution<float> dist_h (0, area.h);
std::random_device rd;
std::default_random_engine gen;
selected.push_back ({
dist_w (gen),
dist_h (gen),
});
auto min_distance = [&selected] (auto q) {
float min_d = INFINITY;
for (auto s: selected)
if (auto s_d = util::distance2 (s, q); s_d < min_d)
min_d = s_d;
return min_d;
};
while (1) {
util::point2f p;
float d = -INFINITY;
for (int i = 0; i < samples; ++i) {
util::point2f candidate { dist_w (gen), dist_h (gen) };
if (auto p_d = min_distance (candidate); p_d > d) {
p = candidate;
d = p_d;
}
}
if (std::sqrt (d) < distance)
break;
selected.push_back (p);
}
return selected;
}

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@ -11,14 +11,15 @@
* See the License for the specific language governing permissions and * See the License for the specific language governing permissions and
* limitations under the License. * limitations under the License.
* *
* Copyright 2015-2017 Danny Robson <danny@nerdcruft.net> * Copyright 2015-2018 Danny Robson <danny@nerdcruft.net>
*/ */
#ifndef __UTIL_GEOM_SAMPLE_HPP #ifndef __UTIL_GEOM_SAMPLE_HPP
#define __UTIL_GEOM_SAMPLE_HPP #define __UTIL_GEOM_SAMPLE_HPP
#include "../coord/fwd.hpp" #include "../coord/fwd.hpp"
#include "./ops.hpp" #include "../extent.hpp"
#include "ops.hpp"
#include <cstddef> #include <cstddef>
@ -72,6 +73,10 @@ namespace util::geom {
{ {
return sampler<S,T,K,G>::fn (k, g); return sampler<S,T,K,G>::fn (k, g);
} }
std::vector<util::point2f>
poisson_sample (util::extent2i, float distance, int samples);
} }
#endif #endif