116 lines
3.3 KiB
C++
116 lines
3.3 KiB
C++
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// Boost.Geometry
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// Copyright (c) 2021, Oracle and/or its affiliates.
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// Contributed and/or modified by Adam Wulkiewicz, on behalf of Oracle
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// Licensed under the Boost Software License version 1.0.
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// http://www.boost.org/users/license.html
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#ifndef BOOST_GEOMETRY_STRATEGY_SPHERICAL_AREA_BOX_HPP
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#define BOOST_GEOMETRY_STRATEGY_SPHERICAL_AREA_BOX_HPP
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#include <boost/geometry/core/coordinate_type.hpp>
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#include <boost/geometry/core/coordinate_dimension.hpp>
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#include <boost/geometry/core/radian_access.hpp>
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#include <boost/geometry/srs/sphere.hpp>
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#include <boost/geometry/strategies/spherical/get_radius.hpp>
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#include <boost/geometry/strategy/area.hpp>
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#include <boost/geometry/util/normalize_spheroidal_box_coordinates.hpp>
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namespace boost { namespace geometry
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{
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namespace strategy { namespace area
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{
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// https://math.stackexchange.com/questions/131735/surface-element-in-spherical-coordinates
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// http://www.cs.cmu.edu/afs/cs/academic/class/16823-s16/www/pdfs/appearance-modeling-3.pdf
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// https://www.astronomyclub.xyz/celestial-sphere-2/solid-angle-on-the-celestial-sphere.html
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// https://mathworld.wolfram.com/SolidAngle.html
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// https://en.wikipedia.org/wiki/Spherical_coordinate_system
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// Note that the equations used in the above articles are spherical polar coordinates.
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// We use spherical equatorial, so the equation is different:
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// assume(y_max > y_min);
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// assume(x_max > x_min);
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// /* because of polar to equatorial conversion */
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// sin(%pi / 2 - y);
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// O: r ^ 2 * cos(y);
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// S: integrate(integrate(O, y, y_min, y_max), x, x_min, x_max);
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template
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<
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typename RadiusTypeOrSphere = double,
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typename CalculationType = void
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>
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class spherical_box
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{
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typedef typename strategy_detail::get_radius
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<
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RadiusTypeOrSphere
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>::type radius_type;
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public:
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template <typename Box>
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struct result_type
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: strategy::area::detail::result_type
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<
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Box,
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CalculationType
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>
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{};
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// For consistency with other strategies the radius is set to 1
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inline spherical_box()
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: m_radius(1.0)
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{}
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template <typename RadiusOrSphere>
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explicit inline spherical_box(RadiusOrSphere const& radius_or_sphere)
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: m_radius(strategy_detail::get_radius
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<
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RadiusOrSphere
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>::apply(radius_or_sphere))
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{}
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template <typename Box>
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inline auto apply(Box const& box) const
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{
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typedef typename result_type<Box>::type return_type;
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return_type x_min = get_as_radian<min_corner, 0>(box); // lon
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return_type y_min = get_as_radian<min_corner, 1>(box); // lat
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return_type x_max = get_as_radian<max_corner, 0>(box);
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return_type y_max = get_as_radian<max_corner, 1>(box);
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if (x_min == x_max || y_max == y_min)
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{
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return return_type(0);
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}
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math::normalize_spheroidal_box_coordinates<radian>(x_min, y_min, x_max, y_max);
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return (x_max - x_min)
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* (sin(y_max) - sin(y_min))
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* return_type(m_radius * m_radius);
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}
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srs::sphere<radius_type> model() const
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{
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return srs::sphere<radius_type>(m_radius);
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}
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private:
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radius_type m_radius;
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};
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}} // namespace strategy::area
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}} // namespace boost::geometry
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#endif // BOOST_GEOMETRY_STRATEGY_SPHERICAL_AREA_BOX_HPP
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