function_signed_distance.h

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// -----------------------------------------------------------------------------
//
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception OR LGPL-2.1-or-later
// Copyright (C) 2021 - 2026 by the deal.II authors
//
// This file is part of the deal.II library.
//
// Detailed license information governing the source code and contributions
// can be found in LICENSE.md and CONTRIBUTING.md at the top level directory.
//
// -----------------------------------------------------------------------------
 
#ifndef dealii_function_signed_distance_h
#define dealii_function_signed_distance_h
 
#include <deal.II/base/config.h>
 
#include <deal.II/base/bounding_box.h>
#include <deal.II/base/function.h>
 
#include <array>
 
DEAL_II_NAMESPACE_OPEN
 
namespace Functions
{
  namespace SignedDistance
  {
    template <int dim>
    class Sphere : public Function<dim>
    {
    public:
      Sphere(const Point<dim> &center = Point<dim>(), const double radius = 1);
 
      double
      value(const Point<dim>  &point,
            const unsigned int component = 0) const override;

      Tensor<1, dim>
      gradient(const Point<dim>  &point,
               const unsigned int component = 0) const override;

      SymmetricTensor<2, dim>
      hessian(const Point<dim>  &point,
              const unsigned int component = 0) const override;
 
    private:
      const Point<dim> center;
      const double     radius;
    };
 

    template <int dim>
    class Plane : public Function<dim>
    {
    public:
      Plane(const Point<dim> &point, const Tensor<1, dim> &normal);
 
      double
      value(const Point<dim>  &point,
            const unsigned int component = 0) const override;
 
      Tensor<1, dim>
      gradient(const Point<dim> &,
               const unsigned int component = 0) const override;
 
      SymmetricTensor<2, dim>
      hessian(const Point<dim> &,
              const unsigned int component = 0) const override;
 
    private:
      const Point<dim>     point_in_plane;
      const Tensor<1, dim> normal;
    };
 

    template <int dim>
    class Ellipsoid : public Function<dim>
    {
    public:
      Ellipsoid(const Point<dim>              &center,
                const std::array<double, dim> &radii,
                const double                   tolerance = 1e-14,
                const unsigned int             max_iter  = 10);
 
      double
      value(const Point<dim>  &point,
            const unsigned int component = 0) const override;

      Tensor<1, dim>
      gradient(const Point<dim> &,
               const unsigned int component = 0) const override;
 
    private:
      double
      evaluate_ellipsoid(const Point<dim> &point) const;

      Point<dim>
      compute_closest_point_ellipse(const Point<dim> &point) const;

      Tensor<1, dim, double>
      compute_analyical_normal_vector_on_ellipse(const Point<dim> &point) const;

      double
      compute_signed_distance_ellipse(const Point<dim> &point) const;
 
      const Point<dim>              center;
      const std::array<double, dim> radii;
      const double                  tolerance;
      const unsigned int            max_iter;
    };
 

    template <int dim>
    class Rectangle : public Function<dim>
    {
    public:
      Rectangle(const Point<dim> &bottom_left, const Point<dim> &top_right);
      Rectangle(const BoundingBox<dim> bounding_box);

      double
      value(const Point<dim>  &p,
            const unsigned int component = 0) const override;
 
    private:
      const BoundingBox<dim> bounding_box;
    };
 

    template <int dim>
    class ZalesakDisk : public Function<dim>
    {
    public:
      ZalesakDisk(const Point<dim> &center,
                  const double      radius,
                  const double      notch_width,
                  const double      notch_height);

      double
      value(const Point<dim>  &p,
            const unsigned int component = 0) const override;
 
    private:
      const Functions::SignedDistance::Sphere<dim> sphere;

      const Functions::SignedDistance::Rectangle<dim> notch;
    };
 

    template <int dim>
    class InfiniteCylinder : public Function<dim>
    {
    public:
      InfiniteCylinder(
        const double          radius,
        const Tensor<1, dim> &axis_direction =
          [] {
            Tensor<1, dim> a;
            a[dim - 1] = 1.0;
            return a;
          }(),
        const Point<dim> &axis_point = Point<dim>());
 
      double
      value(const Point<dim>  &point,
            const unsigned int component = 0) const override;

      Tensor<1, dim>
      gradient(const Point<dim>  &point,
               const unsigned int component = 0) const override;
 
    private:
      const Point<dim>     x0;
      const Tensor<1, dim> axis;
      const double         R;
    };
  } // namespace SignedDistance
} // namespace Functions
 
DEAL_II_NAMESPACE_CLOSE
 
#endif