Construction operations

[Leila: MANTENERE LA DIVAGAZIONE SULLE FONTI DEI DATI]

[ENRICO: NON CAPISCO COS'E' E COSA C'ENTRA QUI. FORSE VA NELLA SEZIONE SU MT-GENERATORS?]

As we already outlined, an MT is built from a sequence of local updates, such as that generated by an incremental technique of terrain generalization. Since many different techniques exist, and no one is best for all applications, we have designed our system to be open to different construction algorithms. In order to achieve this goal, we have included in the MT-manager only generic mechanisms that build an MT data structure starting from a sequence of local updates.

The construction of a Multi-Triangulation is made off-line by modules of the outer layer, called MT-generators, which work in two steps:

1. Generation of an initial TIN and of a sequence of updates which incrementally refine it.
2. Determination of the partial order within the sequence of updates and construction of the MT.

The MT-manager only provides operations that allow an MT-generator recording the updates as they are performed, plus a single operation that automatically transforms the sequence of recorded updates into an MT.

This mechanism is general enough to allow us to transform different iterative techniques for terrain generalization into techniques for generating our multiresolution model, without requiring any knowledge of the MT model and its internal organization. These issues are discussed further in Section .