FIGURE 7.

Internal program structure and control flow of VAST. VAST is structured as a collection of modules (C++ classes) which implement different parts of the program, the most important of which are listed in (A). The internal state of the program is held in a global state system class (B). Layers are kept in a linked list, with each layer holding a set of further class instances depending on type (C). There are two caching systems, one for image data (D) and one for segmentation data (E). All image layers share the image cache and all segmentation layers share the segmentation cache. (F) Shows the threading structure and the control flow of the main thread. Even though each layer has its own loader thread, cache updating is done in the main thread only to prevent multithreading problems.