Gets a value that indicates whether the pipeline is currently in a surface drawing operation. Surface drawing means draw the shaded triangles of a mesh representing the surface (mesh, extrusion, or brep). This is useful when inside of a draw event or display conduit to check and see if the geometry is about to be drawn as a shaded set of triangles representing the geometry. See DrawingWires to check and see if the wireframe representation of the geometry is going to be drawn.