Here is a list of all namespaces with brief descriptions:

[detail level 12]

NBVH
NGraphic3d_TransformUtils	Helper class that implements transformation matrix functionality
▼NIMeshData
NModel
NIVtkTools	Helper methods to facilitate usage of VIS classes in an application
▼Nopencascade	Namespace opencascade is intended for low-level template classes and functions
NFNVHash	Implementation of FNV-1a with autodetect of sizeof(size_t). This function should work on unsigned char, otherwise it does not correctly implement the FNV-1a algorithm. The existing behaviour is retained for backwards compatibility
NMurmurHash	Implementation of Murmur hash with autodetect of sizeof(size_t)
Nstd	Namespace opencascade::std includes templates from C++11 std namespace used by OCCT classes. These definitions are imported from std namespace, plus (on older compilers) from std::tr1, or implemented by custom code where neither std not std::tr1 provide necessary definitions
NOpenGl
NOpenGl_HashMapInitializer
NOpenGl_Raytrace
NRWObj_Tools	Auxiliary tools for OBJ format parser
NSelectMgr_MatOp
Nstd