CashFlow, A Visualization Framework for 3D Flow - Studierstube ...

Software Design3.9. Mapper Nodes3.9 Mapper NodesMapper nodes are used to transform given data into new data. The Mapper node haveread and write access to the MultiData node and DataAccess node.Executing a Mapper node can be triggered by:• Update fieldSome Mappers are only used for pre–processing and will be triggered by a fieldconnection.• Update actionSome Mappers implement costly algorithms like streamline integration of iso–surface creation and thus are triggered by update actions.• Listener on virtual arraySince it may be useful only to update a Mapper if certain data has changed, it isuseful to trigger the Mapper as soon as the data in the virtual array has changed.• On–the–flyOther Mappers may be executed every time the scene graph is traversed. Thiscould be reasonable for the generation of a color–map for instance.Mapper nodes are very important, because they implement a large number of visualizationalgorithms. The complexity of Mapper nodes can be categorized in 3 levels:• Low complexityAll algorithms operating directly on the raw data without support of grid topology.Examples are color mapping and parameterization of data.• Medium complexityAll algorithms operating on the raw data with support of grid topology. Examplesare iso–surface extraction.• High complexityAlgorithms requesting grid topology data and results form the medium complexitylevel as input. Examples are vortex detection and flow field topologycalculation, which are not supported by CashFlow yet.After this introduction to the four kinds of update mechanism and the subdivisionbased on the complexity of the algorithm we want to describe the different types ofMapper nodes used in the CashFlow framework.• Color MapperScalar or vector data is mapped to color. These are low complexity algorithms.• Data MapperData is used to create new data without respect to the type of grid and its topology.These are also low complexity algorithms.61