Negates this vector. 
   Namespace:   Autodesk.Revit.DB  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 2015.0.0.0 (2015.0.0.0) 
Syntax
Return Value
The vector opposite to this vector.Remarks
 The negated vector is obtained by changing the sign of each coordinate of this vector.