Returns the thickness of the circle entity (DXF 39) in drawing units. Thickness is the extrusion length along the normal. A positive value defines the thickness to be drawn along the normal direction. A negative value defines the thickness to be drawn in the opposite direction from the normal. A zero value defines a circle without thickness.

Example of Working with the Circle Object 

Specific Circle Properties 

OdDbCircle::setThickness() method

OdDbCircle Methods