💿🐜 Antkeeper source code
https://antkeeper.com
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90 lines
2.8 KiB
90 lines
2.8 KiB
/*
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* Copyright (C) 2023 Christopher J. Howard
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*
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* This file is part of Antkeeper source code.
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*
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* Antkeeper source code is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* Antkeeper source code is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with Antkeeper source code. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef ANTKEEPER_GEOM_CLOSEST_FEATURE_HPP
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#define ANTKEEPER_GEOM_CLOSEST_FEATURE_HPP
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#include <engine/geom/primitives/point.hpp>
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#include <engine/geom/primitives/triangle.hpp>
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#include <algorithm>
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#include <tuple>
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namespace geom {
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/**
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* Calculates the closest features on a triangle to a point.
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*
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* @tparam T Real type.
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*
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* @param tri Triangle.
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* @param a First point of triangle.
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* @param b Second point of triangle.
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* @param c Third point of triangle.
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* @param p Point.
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*
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* @return Tuple containing the Barycentric coordinates of the closest point on the triangle to point @p p, followed by the index of the edge on which the point lies (`-1` if not on an edge).
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*/
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/// @{
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template <class T>
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[[nodiscard]] constexpr std::tuple<point<T, 3>, int> closest_feature(const point<T, 3>& a, const point<T, 3>& b, const point<T, 3>& c, const point<T, 3>& p) noexcept
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{
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const auto ab = b - a;
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const auto ca = a - c;
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const auto ap = p - a;
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const auto n = math::cross(ab, ca);
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const auto d = math::sqr_length(n);
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const auto q = math::cross(n, ap);
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point<T, 3> uvw;
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if ((uvw.z() = math::dot(q, ab) / d) < T{0})
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{
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uvw.z() = T{0};
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uvw.y() = std::min<T>(std::max<T>(math::dot(ab, ap) / math::sqr_length(ab), T{0}), T{1});
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uvw.x() = T{1} - uvw.y();
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return {uvw, 0};
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}
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else if ((uvw.y() = math::dot(q, ca) / d) < T{0})
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{
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uvw.y() = T{0};
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uvw.x() = std::min<T>(std::max<T>(math::dot(ca, p - c) / math::sqr_length(ca), T{0}), T{1});
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uvw.z() = T{1} - uvw.x();
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return {uvw, 2};
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}
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else if ((uvw.x() = T{1} - uvw.y() - uvw.z()) < T{0})
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{
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uvw.x() = T{0};
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const auto bc = c - b;
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uvw.z() = std::min<T>(std::max<T>(math::dot(bc, p - b) / math::sqr_length(bc), T{0}), T{1});
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uvw.y() = T{1} - uvw.z();
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return {uvw, 1};
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}
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return {uvw, -1};
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}
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template <class T>
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[[nodiscard]] inline constexpr std::tuple<point<T, 3>, int> closest_feature(const triangle<T, 3>& tri, const point<T, 3>& p) noexcept
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{
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return closest_feature(tri.a, tri.b, tri.c, p);
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}
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/// @}
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} // namespace geom
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#endif // ANTKEEPER_GEOM_CLOSEST_FEATURE_HPP
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