MeshlessMedusa/include/medusa/bits/domains/NURBSShape_fwd.hpp

#ifndef MEDUSA_BITS_DOMAINS_NURBSSHAPE_FWD_HPP_
#define MEDUSA_BITS_DOMAINS_NURBSSHAPE_FWD_HPP_

/**
 * @file
 * Declaration of NURBSShape class.
 *
 * @example test/domains/NURBSShape_test.cpp
 */

#include <medusa/Config.hpp>
#include <medusa/bits/domains/DomainShape_fwd.hpp>
#include <medusa/bits/types/Vec.hpp>
#include <medusa/bits/types/Range.hpp>
#include <medusa/bits/domains/NURBSPatch_fwd.hpp>
#include <medusa/bits/utils/randutils.hpp>

namespace mm
{

    /**
     * Implementation details of NURBSShape, contains structures for partial class specialization.
     */
    namespace nurbs_shape_internal
    {
        /**
         * Internal structure of NURBSShape that helps with partial class specialization.
         * All of its functions have the same signature (apart from accepting a reference to NURBSShape)
         * as the corresponding functions of NURBSShape. NURBSShape holds an instance of this class
         * and calls its functions when specialized functions are requested.
         *
         * Note: partial class specialization can also be done by having a base class with functions,
         * that are not specialized (NURBSShapeBase) and a fully specialized class (NURBSShape) that
         * inherits from it. This approach was chosen to keep Medusa's class hierarchy cleaner.
         */
        template <typename vec_t, typename param_vec_t>
        struct NURBSShapeHelper
        {
        };
    } // namespace nurbs_shape_internal

    /**
     * Class representing a shape made out of NURBS patches in an arbitrary dimensional space.
     *
     * @warning Currently only supports NURBS surfaces (2D domain) and NURBS
     * curves (1D domain).
     *
     * Usage example:
     * @snippet domains/NURBSShape_test.cpp NURBSShape usage example
     *
     * @tparam vec_t Vector type.
     *
     * @ingroup domains
     */
    template <typename vec_t, typename param_vec_t>
    class NURBSShape : public DomainShape<vec_t>
    {
        friend struct nurbs_shape_internal::NURBSShapeHelper<vec_t, param_vec_t>;

    public:
        typedef typename vec_t::scalar_t scalar_t; ///< Scalar type.
        /// Store dimensionality.
        enum
        { /** Dimensionality of space after projection. */ dim = vec_t::dim,
          /** Dimensionality of space before projection. */ proj_dim = dim + 1,
          /** Dimensionality of parametric space. */ param_dim = param_vec_t::dim };
        typedef Vec<scalar_t, proj_dim> proj_vec_t; ///< Vector type before projection.

    private:
        Range<NURBSPatch<vec_t, param_vec_t>> patches; ///< Range of NURBS patches.
        int max_points = 500000;                       ///< Maximal number of points generated in surface fill.
        int seed_;                                     ///<  Seed for the random number generator.
        int n_samples = 15;                            ///< Number of samples in surface fill.
        scalar_t zeta = 1 - 1e-10;                     ///< Proximity tolerance in surface fill.
        scalar_t epsilon = 0;                          ///< Evaluate normals slightly away from the boundary.

    public:
        /// Construct NURBSShape from a Range of patches.
        NURBSShape(const Range<NURBSPatch<vec_t, param_vec_t>> &patches_in);

        bool contains(const vec_t & /* point */) const override { return true; }

        bool hasContains() const override { return false; }

        std::pair<vec_t, vec_t> bbox() const override
        {
            assert_msg(false, "This function is not available for this shape. A"
                              "bounding box of its DomainDiscretization should be taken.");
            return {};
        }

        DomainDiscretization<vec_t> discretizeBoundaryWithDensity(
            const std::function<scalar_t(vec_t)> &, int) const override;

        std::ostream &print(std::ostream &ostream) const override
        {
            return ostream << "NURBS shape made of " << patches.size() << " patches.";
        }

        NURBSShape *clone() const override
        {
            return new NURBSShape<vec_t, param_vec_t>(*this);
        }

        /** Maximal number of points generated in surface fill
         * @warning The actual upper bound for number of points generated is maxPoints @f$\pm@f$
         * numSamples.
         */
        NURBSShape &maxPoints(int max_points)
        {
            this->max_points = max_points;
            return *this;
        }

        /// Set custom seed for the random number generator.
        NURBSShape &seed(int seed)
        {
            seed_ = seed;
            return *this;
        }

        /** Set proximity tolerance in surface fill.
         * A new candidate mush be at least `zeta*h(p)` away. It should hold that `0 < zeta < 1`.
         */
        NURBSShape &proximityTolerance(scalar_t zeta);

        /**
         * Controls the number of generated candidates from each point in surface fill.
         * For 2-D it is the actual number
         * of candidates, for 3-D it is the number of candidates on the great circle. Its value
         * is ignored in 1-D.
         */
        NURBSShape &numSamples(int n_samples)
        {
            this->n_samples = n_samples;
            return *this;
        }

        /**
         * Calculate boundary normals `epsilon` times the size of domain away from the boundary.
         * By default `epsilon = 0`. This can be useful if normals are undefined on the boundary.
         * It should hold that `0 < epsilon < 1`.
         */
        NURBSShape &boundaryProximity(scalar_t epsilon);
    };

} // namespace mm

#endif // MEDUSA_BITS_DOMAINS_NURBSSHAPE_FWD_HPP_