Decouples evaluation of a piecewise_function from the function itself (#5344)

src/ifcgeom/piecewise_function_evaluator.h

@@ -0,0 +1,58 @@
+#ifndef ITERATOR_PWF_EVALUATOR_H
+#define ITERATOR_PWF_EVALUATOR_H
+
+#include "../ifcgeom/taxonomy.h"
+
+#include <boost/function.hpp>
+
+namespace ifcopenshell { namespace geometry {
+
+/// @brief utility class to evaluate piecewise_function objects
+class piecewise_function_evaluator {
+  public:
+    piecewise_function_evaluator(taxonomy::piecewise_function::const_ptr pwf, ifcopenshell::geometry::Settings* settings=nullptr);
+
+    /// @brief returns a vector of "distance along" points where the evaluate function computes loop points
+    std::vector<double> evaluation_points() const;
+
+    /// @brief returns a vector of "distance along" points between ustart and uend
+    /// @param ustart starting location
+    /// @param uend ending location
+    /// @param nsteps number of steps to evaluate
+    std::vector<double> evaluation_points(double ustart, double uend, unsigned nsteps) const;
+
+    /// @brief evaluates the piecewise function between start and end
+    /// evaluation point step size is taken from the settings object
+    taxonomy::item::ptr evaluate() const;
+
+    /// @brief evaluates the piecewise function between ustart and uend
+    /// if ustart and uend are out of range, the range of values evaluated
+    /// are constrained to start_ and start_+length_
+    /// @param ustart starting location
+    /// @param uend ending location
+    /// @param nsteps number of steps to evaluate
+    /// @return taxonomy::loop::ptr
+    taxonomy::item::ptr evaluate(double ustart, double uend, unsigned nsteps) const;
+
+    /// @brief evaluates the piecewise function at u
+    /// @param u u is constrained to be between start_ and start_+length
+    /// @return 4x4 placement matrix
+    Eigen::Matrix4d evaluate(double u) const;
+
+  private:
+    taxonomy::item::ptr evaluate(const std::vector<double>& dist) const;
+    std::tuple<double, double, const std::function<Eigen::Matrix4d(double u)>*> get_span(double u) const;
+
+    taxonomy::piecewise_function::const_ptr pwf_;
+
+    ifcopenshell::geometry::Settings settings_;
+
+    mutable double current_span_start_ = 0;
+    mutable double current_span_end_ = 0;
+    mutable const std::function<Eigen::Matrix4d(double u)>* current_span_fn_ = nullptr;
+    mutable boost::optional<std::vector<double>> eval_points_;
+};
+
+}}
+
+#endif