Ponca is designed to be lightweight and easy to integrate in existing code bases. To achieve this goal:

Ponca does not include datastructures to represent and store point cloud data, and let clients defining how to store and access data,
Ponca cannot rely on C++ polymorphism to define its API: most computational objects used through the library involve very small computation. Combining these computation using polymorphism requires to use virtual functions, which introduce a very high overhead (considering the small computation of each class).
Instead, Ponca is based on 'Concepts' that need to be followed to use/extend the library.

Hence, we expect client code to define how point data can be accessed, by respecting the following interface:

        class PointConcept {
        public:
            /* \brief Defines the ambient space dimension, 3 in this example */
            enum {
                Dim = 3
            };
            // \brief Defines the type used ton encode scalar values
            typedef float Scalar;
            // \brief Defines type used ton encode vector values
            typedef Eigen::Matrix<Scalar, Dim, 1> VectorType;
 
            // \brief Default constructor
            PONCA_MULTIARCH inline PointConcept();
 
            // \brief Read access to the position property
            // \note The return type should have the same API than VectorType (e.g. const Eigen::Map< const VectorType >&),
            // or be implicitly convertible to VectorType
            PONCA_MULTIARCH inline const VectorType& pos() const;
 
            // \brief Write access to the position property
            // \note Same constraints on return type
            PONCA_MULTIARCH inline VectorType& pos();
        }; //class PointConcept

This represents the minimal API required to use Ponca:

an integer Dim defining the number of dimensions of the ambient space (3 for 3d point clouds)
types Scalar and VectorType that will be used by the library to represent scalars and vectors
a default constructor
read and read/write access to an attribute describing the position of a point (pos())

Depending on the use cases, other types (e.g. MatrixType) or accessors (normal()) might be required.

See also: Example Ponca data-structure binding, that demonstrate how to implement PointConcept in order to access point data in existing arrays without duplication.

See concepts used in each modules:

Fitting module: Concepts

[Go back to user manual]