Flow visualisation is an attractive topic in data visualisation

Flow visualization has been a very attractive component of scientific visualization research for a long time.Usually very large multivariate datasets require processing. These datasets often consist of a large number of sample locations and several time steps. The steadily increasing performance of computers has recently become a driving factor for a reemergence in flow visualization research, especially in texture-based techniques. In this paper, dense, texture-based flow visualization techniques are discussed. This class of techniques attempts to provide a complete, dense representation of the flow field with high spatio-temporal coherency. An attempt of categorizing closely related solutions is incorporated and presented. Fundamentals are shortly addressed as well as advantages and disadvantages of the methods.

In this paper we explore a novel combined application of two of our existing visualisation techniques to thetracking of 3D vortex tubes in an unsteady flow. The applied techniques are the winding‐angle vortex extractiontechnique based on streamline geometry, and the attribute‐based feature tracking technique. We have applied theseto the well‐known case of an unsteady 3D flow past a tapered cylinder. First, 2D vortices are detected in a number of horizontal slices for each time step, by means of the winding‐anglevortex extraction method. For each 2D vortex a number of attributes are calculated and stored. These vorticesare visualised by a special type of ellipse icons, showing the position, shape and rotational direction and speed ineach slice. Next, for each time step, 3D vortex tubes are constructed from the 2D vortices by applying the feature trackingprocedure in a spatial dimension to connect the corresponding vortices in adjacent slices. The result is a graphattribute set with the 2D vortex attributes in the nodes and the spatial correspondences as edges. Finally, the 3D vortex tubes are tracked in time using the same tracking procedure, for finding the correspondingtubes in successive time steps. The result is a description of the evolution of the 3D vortices. An interactive, time‐dependentvisualisation is generated using the temporal correspondences of each vortex tube. This analysis revealsa number of interesting patterns. ACM CSS: I.3.8 Computer Graphics—Applications

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