mfunc.h

#pragma once
 
#include <cgv/math/vec.h>
 
namespace cgv {
        namespace math {
 
template <typename X, typename T>
class mfunc
{
public:
        typedef cgv::math::vec<X> pnt_type;
        typedef cgv::math::vec<X> vec_type;
        virtual ~mfunc() {}
        virtual unsigned get_nr_independent_variables() const = 0;
        virtual T evaluate(const pnt_type& p) const = 0;
        virtual vec_type evaluate_gradient(const pnt_type& p) const {
                static X epsilon   = (X)1e-5;
                static X inv_2_eps = (X)(0.5/epsilon);
                unsigned n = p.size();
                vec_type g(n);
                pnt_type q(p);
                for (unsigned i=0; i<n; ++i) {
                        q(i) += epsilon;
                        g(i)  = evaluate(q);
                        q(i)  = p(i)-epsilon;
                        g(i) -= evaluate(q);
                        g(i) *= inv_2_eps;
                        q(i)  = p(i);
                }
                return g;
        }
};
 
template <typename X, typename T>
class v2_func : public mfunc<X,T>
{
public:
        unsigned int get_nr_independent_variables() const { return 2; }
};
 
template <typename X, typename T>
class v3_func : public mfunc<X,T>
{
public:
        unsigned int get_nr_independent_variables() const { return 3; }
};
 
        }
}