libcruft-util/geom/sample.hpp

78 lines
2.2 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 2015-2017 Danny Robson <danny@nerdcruft.net>
*/
#ifndef __UTIL_GEOM_SAMPLE_HPP
#define __UTIL_GEOM_SAMPLE_HPP
#include "../coord/fwd.hpp"
#include "./ops.hpp"
#include <cstddef>
///////////////////////////////////////////////////////////////////////////////
namespace util::geom {
/// a function object that selects a uniformly random point inside a shape
/// using a provided random generator. the point will lie within the shape,
/// inclusive of boundaries.
///
/// may be specialised for arbitrary shapes but uses rejection sampling
/// as a safe default. this implies that execution may not take a constant
/// time.
///
/// \tparam S coordinate type dimension
/// \tparam T value type for the shape/coordinate
/// \tparam K the shape type to test
/// \tparam G a UniformRandomBitGenerator, eg std::min19937
template <
size_t S,
typename T,
template <size_t,typename> class K,
typename G
>
struct sampler {
static point<S,T>
fn (K<S,T> k, G &g)
{
auto b = bounds (k);
while (true) {
auto p = sample (b, g);
if (intersects (k, p))
return p;
}
}
};
///////////////////////////////////////////////////////////////////////////
/// a convenience function that calls sample::fn to select a random point
/// in a provided shape.
template <
size_t S,
typename T,
template <size_t,typename> class K,
typename G // random generator
>
point<S,T>
sample (K<S,T> k, G &g)
{
return sampler<S,T,K,G>::fn (k, g);
}
}
#endif