70 lines
2.1 KiB
C
70 lines
2.1 KiB
C
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#pragma once
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#include <cgv/math/vec.h>
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namespace cgv {
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namespace math {
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/** interface class for multivariate function with two template arguments:
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- X defines the type of the independent variables and
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- T the type of range to which the function maps
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For example a function that maps from n double variables to an int
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would be declared as mfunc<double,int>
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*/
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template <typename X, typename T>
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class mfunc
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{
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public:
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/// points must have get_nr_independent_variables() components
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typedef cgv::math::vec<X> pnt_type;
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/// vectors must have get_nr_independent_variables() components
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typedef cgv::math::vec<X> vec_type;
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/// virtual destructor
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virtual ~mfunc() {}
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/// return the number of independent variables that are mapped by the function
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virtual unsigned get_nr_independent_variables() const = 0;
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/// interface for evaluation of the multivariate function
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virtual T evaluate(const pnt_type& p) const = 0;
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/** interface for evaluation of the gradient of the multivariate function.
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default implementation uses central differences to
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approximate the gradient, with an epsilon of 1e-5. */
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virtual vec_type evaluate_gradient(const pnt_type& p) const {
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static X epsilon = (X)1e-5;
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static X inv_2_eps = (X)(0.5/epsilon);
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unsigned n = p.size();
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vec_type g(n);
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pnt_type q(p);
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for (unsigned i=0; i<n; ++i) {
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q(i) += epsilon;
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g(i) = evaluate(q);
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q(i) = p(i)-epsilon;
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g(i) -= evaluate(q);
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g(i) *= inv_2_eps;
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q(i) = p(i);
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}
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return g;
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}
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};
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/** specialization of a multivariate function to two independent variables,
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which only reimplements the method get_nr_independent_variables. */
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template <typename X, typename T>
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class v2_func : public mfunc<X,T>
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{
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public:
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/// returns 2
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unsigned int get_nr_independent_variables() const { return 2; }
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};
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/** specialization of a multivariate function to three independent variables,
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which only reimplements the method get_nr_independent_variables. */
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template <typename X, typename T>
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class v3_func : public mfunc<X,T>
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{
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public:
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/// returns 3
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unsigned int get_nr_independent_variables() const { return 3; }
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};
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}
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}
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