Curve Geometry
A Curve Geometry presents a mathematical 3D line in an entity, i.e. it adds 
    properties necessary for a line to become part of a model 
Curve Geometry wraps a reference to a generic 3D curve or line. 
To create a Curve Geometry at runtime, call 
IObjectGenerator_DG.Create<ICurveGeometry_DG>() to obtain ICurveGeometry_DG. 
             
	
        Use methods of ILineSection_DG to attach a line to the Line Entity. 
        Use properties and interfaces relevant to the specific mathematical curve to 
        modify geometry of the curve. 
             
	
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