Depending on circumstances, interactively picked family instance geometry may be returned in the global Revit world coordinate system WCS, or in the family instance definition local coordinate system LCS.A family instance may have its own non-empty solid, or use the symbol geometry. The symbol geometry requires keeping track of the instance transform to map it to the actual instance project location Question on Incorrect Face Normal Working Plane has no Effect Non-Picked Face Normals are Correct Solution Detecting When to Use LCS versus WCS Retrieval of Picked Geometry Face from Instance is Untransformed...

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