Opacity Optimization For Surfaces

In flow visualization, integral surfaces rapidly tend to expand, fold and produce vast amounts of occlusion. While silhouette enhancements and local transparency mappings proved useful for semi-transparent depictions, they still introduce visual clutter when surfaces grow more complex. An effective visualization of the flow requires a balance between the presentation of interesting surface parts and the avoidance of occlusions that hinder the view. In this paper, we extend the concept of opacity optimization to surfaces to obtain a global approach to the occlusion problem. Starting with a partition of the surfaces into patches, we compute per-patch opacity as minimizer of a bounded-variable least-squares problem. For the final rendering, opacity is interpolated on the surfaces. The resulting visualization technique is interactive, frame-coherent, view-dependent and driven by domain knowledge.