Geom classes and gp classes

There are two distinct sets of classes to describe geometric entities in Open CASCADE:

• gp contains classes like gp_Pln, gp_Circle, gp_Lin
• Geom contains classes like Geom_Plane, Geom_Circle or Geom_Line

Geom is designed for parametrized description of geometry, while gp contains effective descriptions, so to speak. gp describes a line using a point on the line as well as the direction. Geom defines a line as a straight curve having a valid parameter value range of [double_min, double_max] (double_min and double_max being the minimum and maximum value for double precision float variables).