SurfaceBuilder

Surface features: it is assumed that any two input surfaces within a group either have a strict containment relationship, or are not overlapping.

Contains the output surfaces.

All but one geometrically identical surface will be output through the Unused port. Two surfaces are considered geometrically identical if their geometries match exactly.

Non-geometry properties like coordinate systems, measures, traits, and geometry names are not considered when matching input geometries.

Non-surface features

Leaving this parameter blank causes the entire set of input surfaces to form a single group. Alternatively, this parameter allows you to select attributes on which to form groups of surface features – each set of features that have the same value for all of these attributes will be processed independently in a group.

Process At End (Blocking): This is the default behavior. Processing will only occur in this transformer once all input is present.

Process When Group Changes (Advanced): This transformer will process input groups in order. Changes of the value of the Group By parameter on the input stream will trigger processing on the currently accumulating group. This may improve overall speed (particularly with multiple, equally-sized groups), but could cause undesired behavior if input groups are not truly ordered.

Considerations for Using Group By

There are two typical reasons for using Process When Group Changes (Advanced) . The first is incoming data that is intended to be processed in groups (and is already so ordered). In this case, the structure dictates Group By usage - not performance considerations.

The second possible reason is potential performance gains.

Performance gains are most likely when the data is already sorted (or read using a SQL ORDER BY statement) since less work is required of FME. If the data needs ordering, it can be sorted in the workspace (though the added processing overhead may negate any gains).

Sorting becomes more difficult according to the number of data streams. Multiple streams of data could be almost impossible to sort into the correct order, since all features matching a Group By value need to arrive before any features (of any feature type or dataset) belonging to the next group. In this case, using Group By with Process At End (Blocking) may be the equivalent and simpler approach.

Note: Multiple feature types and features from multiple datasets will not generally naturally occur in the correct order.

As with many scenarios, testing different approaches in your workspace with your data is the only definitive way to identify performance gains.

This parameter indicates whether or not surface features used to cut other surfaces should be dropped or output.

This parameter will be added to each output feature and will contain "yes" if that feature was used to cut a hole inside some other feature, and "no" if that feature did not cut into any other features.

If a hole list name is specified, the attributes of the features that were used to cut holes in this surface are added to this attribute list.

If set to Yes, the Normal Tolerance in Degrees and Offset Tolerance parameters are enabled. If set to No, the two parameters are disabled.

Faces must be parallel before they are allowed to cut into each other. If two faces are nearly parallel with normals that are slightly apart, use this parameter to set a tolerance in degrees. The larger the value, the less parallel the faces would have to be while still considered parallel to each other.

Usage Tip: Use this parameter together with Offset Tolerance.

Faces must be co-planar before they are allowed to cut into each other. If two faces are nearly co-planar, but are a small offset from each other, use this parameter to set a tolerance in ground units. The larger the value, the farther away the faces could be while still considered co-planar.

Usage Tip: Use this parameter together with Normal Tolerance in Degrees.