Animation aspects

As fourth part of stream surface enhancement we apply animation to certain parts of the visual representation. As stream arrows are implemented in the scope of the DynSys3D system (see Chapter 8), which itself is based on AVS [2], animation is well-supported. AVS allows to export certain module parameters as input ports. Furthermore there are already some basic animation modules available as, e.g., animated integer or animated float. Connecting such a module to an exported module parameter is the simplest method of animating a visualization setup.

Several parameters can be animated to improve the visualization. An animated offset vector o (see Sect. 4.3 and Fig. 4.8) is used to move stream arrows along stream lines within the stream surface. Composing the tiles of the texture in a regular manner, just a few images of the animation sequence have to be rendered. A longer sequence can be produced by looping the cyclic sequence several times.

Other sequences are rendered by animating the construction of a stream surface. The temporal evolution of a stream surface starting from an initial set of colinear points is illustrated. Taking the stream surface of the mixed-mode oscillations model to be opaque clearly shows how some parts of the model representation severely occlude other portions. With stream arrows this unsatisfactory situation is improved. The animation of the stream surface evolution gives a good impression of the dynamics induced by the given dynamical system. The removal of certain parts of the model can be animated as well. A simulated process of successively removing more and more parts of the stream surface is easier to interpret than still images where parts of the model have been removed. Another animation sequence we rendered shows such a process--a cut plane is used to distinguish semi-transparent parts of the stream surface above the plane from opaque areas below. During the animation the plane is moved towards the center of the model, so that successively most parts of the stream surface become visible. Many other parameters are suitable to be animated. Moving the viewpoint around the model does certainly help to understand the system behavior. The initial curve of the constructed stream surface may be moved to demonstrate stability features of the dynamical system. This corresponds to successively displaying not only one but various adjacent stream surfaces. The stream lines used to enhance the edges of the stream surface could be animated by moving their origins along the line of initial conditions. This would improve the visualization of the flow within a stream surface.

mailto:helwig@cg.tuwien.ac.at.