DEMGenerator

These input features may be 2D or 3D. Other than points, lines and area geometries, they may also be raster, point cloud, and aggregate geometries.

2D features will be forced to 3D by adding a z value of 0. In most cases, all points extracted from this port will be found in the vertex pool of the underlying surface model. A minimum of 3 unique points are required to construct a surface model. Points with duplicate x and y values will be dropped.

These input features may be 2D or 3D, and may reside inside an aggregate structure.

2D features will be forced to 3D by adding a z value of 0. Breakline edges will be found in the edge pool of the underlying surface model. Sometimes, a breakline edge will be split up to allow an optimal triangulation of the surface model. Points with duplicate x and y values will be dropped.

This output port samples the underlying surface model according to the sampling rates specified in Output DEM X Cell Spacing, and Output DEM Y Cell Spacing, and produces a set of evenly spaced 3D points.

This parameter allows groups to be formed by attribute values. Zero or more attributes may be specified.

Input features with the same attribute values are placed into the same group. The transformer then operates independently on each group of input features.

If this parameter is left blank, the transformer will treat the entire set of input features as one group.

Note: How parallel processing works with FME: see About Parallel Processing for detailed information.

This parameter determines whether or not the transformer should perform the work across parallel processes. If it is enabled, a process will be launched for each group specified by the Group By parameter.

Parallel Processing Levels

For example, on a quad-core machine, minimal parallelism will result in two simultaneous FME processes. Extreme parallelism on an 8-core machine would result in 16 simultaneous processes.

You can experiment with this feature and view the information in the Windows Task Manager and the Workbench Log window.

No: This is the default behavior. Processing will only occur in this transformer once all input is present.

By Group: This transformer will process input groups in order. Changes on the value of the Group By parameter on the input stream will trigger batch processing on the currently accumulating group. This will improve overall speed if groups are large/complex, but could cause undesired behavior if input groups are not truly ordered.

This parameter is used to determine which input points to add to the surface model as vertices. Specifying a value of 0 turns off vertex filtering.

Tip: A larger value will speed up surface model construction. The larger the value, the more input points will be filtered out. For input files with millions – or even billions – of points, it becomes essential to increase this value.

When a positive value for surface tolerance is specified, it works as follows. For each vertex that is being added to the model:

• If the x,y location is outside the 2D convex hull of the existing surface model, it is added to the model.
• If the x,y location is inside the 2D convex hull of the existing surface model:
  • The difference between the z value from the existing surface model and the z value of the vertex is calculated.
  • This difference is compared to the surface model tolerance.
  • The vertex is only added to the surface model if the difference is greater than the surface tolerance; otherwise, the vertex is discarded.

This parameter is used for the output ports DEMPoints and DEMRaster when these output ports exist on the transformer. It is also used if DrapeFeatures are input to the model.

• AUTO: The transformer will calculate each output point automatically. The PLANAR method is used if the output point is within a surface triangle in xy and the CONSTANT method is used otherwise.
• PLANAR: Barycentric interpolation is used to determine the z value for each output point. If an output point is outside the 2D convex hull of the surface model, the output z value will be set to NaN (Not a Number).
• CONSTANT: The z value of each output point is set to the z value of the closest vertex in the underlying model.

This parameter specifies the name of an elevation attribute for the output ports Contours and DEMPoints, when these output ports exist on the transformer.

These parameters specify the x and y sampling intervals for the output DEMPoints.