SurfaceDraper

From Fmepedia

SurfaceDraper is a Workbench Transformer.

Interpolates z coordinates and adds them to DRAPED_FEATURES based on the underlying surface defined by the POINTS, 3D_LINES, and BREAKLINES.

If the incoming DRAPE_FEATURES are 2D, then the z elevation is added. If the incoming DRAPE_FEATURES are 3D, then the z coordinates are replaced with new ones.

The underlying surface is built using the z tolerance as specified by the Tolerance parameter. This should be set to the larger of the accuracy of the elevation data being input and the accuracy of the output elevation that is required.

The Drape Type parameter determines if z elevations are only added where there is a vertex on the input DRAPE_FEATURES or if coordinates should be added wherever the underlying model determines a change in slope. If VERTEX is specified, then the output DRAPED_FEATURES will have the same number of vertices as they had when they were input. If MODEL is specified, then additional vertices are added at each slope change.

The Interpolation Type parameter defines how the z elevation is determined. If CONSTANT is specified, then the z elevation of each coordinate is set to be the elevation of the closest model point. If PLANAR is set, then interpolation is used to determine the elevation.

The SurfaceModeller has a similar option.