line-segment.hpp

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/*
 * Copyright (C) 2023  Christopher J. Howard
 *
 * This file is part of Antkeeper source code.
 *
 * Antkeeper source code is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Antkeeper source code is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Antkeeper source code.  If not, see <http://www.gnu.org/licenses/>.
 */
 
#ifndef ANTKEEPER_GEOM_PRIMITIVES_LINE_SEGMENT_HPP
#define ANTKEEPER_GEOM_PRIMITIVES_LINE_SEGMENT_HPP
 
#include <engine/math/vector.hpp>
 
namespace geom {
namespace primitives {
 
template <class T, std::size_t N>
struct line_segment
{
    using vector_type = math::vector<T, N>;
    
    vector_type a;
    
    vector_type b;
    
    [[nodiscard]] inline T sqr_length() const noexcept
    {
        return math::sqr_distance(a, b);
    }
    
    [[nodiscard]] inline T length() const noexcept
    {
        const T d = sqr_length();
        return d ? std::sqrt(d) : d;
    }
    
    [[nodiscard]] T sqr_distance(const vector_type& point) const noexcept
    {
        const vector_type ab = b - a;
        const vector_type ap = point - a;
        
        const T t = math::dot(ap, ab);
        if (t <= T{0})
        {
            return math::sqr_length(ap);
        }
        
        const T ab_sqr_length = math::sqr_length(ab);
        if (t >= ab_sqr_length)
        {
            return math::sqr_length(point - b);
        }
        
        return math::sqr_length(ap) - (t * t) / ab_sqr_length;
    }
    
    [[nodiscard]] inline T distance(const vector_type& point) const
    {
        const T d = sqr_distance(point);
        return d ? std::sqrt(d) : d;
    }
};
 
} // namespace primitives
 
using namespace primitives;
 
} // namespace geom
 
#endif // ANTKEEPER_GEOM_PRIMITIVES_LINE_SEGMENT_HPP