Automatic Stream Surface Seeding: A Feature Centered Approach

The ability to capture and visualize information within the flow poses challenges for visualizing 3D flow fields. Stream surfaces are one of many useful integration based techniques for visualizing 3D flow. However seeding integral surfaces can be challenging. Previous research generally focuses on manual placement of stream surfaces. Little attention has been given to the problem of automatic stream surface seeding. This paper introduces a novel automatic stream surface seeding strategy based on vector field clustering. It is important that the user can define and target particular characteristics of the flow. Our framework provides this ability. The user is able to specify different vector clustering parameters enabling a range of abstraction for the density and placement of seeding curves and their associated stream surfaces. We demonstrate the effectiveness of this automatic stream surface approach on a range of flow simulations and incorporate illustrative visualization techniques. Domain expert evaluation of the results provides valuable insight into the users requirements and effectiveness of our approach. 1. Introduction Flow visualization is an important and powerful means for analyzing , exploring and communicating simulation or experimental results. Flow visualization results can differ in their complexity, quality and style [PVH * 03] [LHZP07] [PL09]. Stream surfaces have become increasingly popular in recent years, and have important inherent characteristics that can enhance the visual perception of complex flow structures [MLP * 10]. Lighting and shading reinforce the perception of shape and depth, images or textures can be mapped to the surface primitives providing additional visual information , color and transparency can be used to convey additional data attributes. Surfaces in general are able to not only capture the features within the flow, but also have the inherent ability to convey further information about the local attributes of the flow [LGD * 05]. This combined with the reduction in visual clutter when compared to using glyphs or streamlines, significantly enhances the utility of surfaces for practitioners. A stream surface is the integration of a one dimensional curve through 3D steady flow. The resulting surface is everywhere tangent to the local flow. Since there is no normal component of the velocity along stream surfaces, thus they are useful for separating distinct regions of similar flow behavior. In practical applications [Hul92] [GTS * 04] a discretized approximation of the stream surface is constructed by integrating discretized seeding curves through the vector field. Stream surfaces for visualization face many challenges. …