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; }
};
 
    }
}