softening.hpp

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#pragma once

 
#include <cmath>
 
#include "orrery/core/types.hpp"
 
namespace orrery::core {

class Softening {
public:
    constexpr Softening() noexcept = default;

    constexpr explicit Softening(Real length) noexcept : squared_(length * length) {}

    [[nodiscard]] constexpr Real squared() const noexcept { return squared_; }
 
    [[nodiscard]] Real length() const noexcept { return std::sqrt(squared_); }
 
private:
    Real squared_{};
};

[[nodiscard]] inline Real softened_inverse_distance(Real separation_squared,
                                                    Softening softening) noexcept {
    return Real{1} / std::sqrt(separation_squared + softening.squared());
}

[[nodiscard]] inline Real softened_inverse_distance_cubed(Real separation_squared,
                                                          Softening softening) noexcept {
    const Real inverse = softened_inverse_distance(separation_squared, softening);
    return inverse * inverse * inverse;
}
 
} // namespace orrery::core