Line integral convolution (LIC), introduced by Cabral and Leedom (1993) is a powerful technique for imaging and animating vector fields. We extend the LIC technique in three ways. Firstly the existing algorithm is limited to vector fields over a regular Cartesian grid. We extend the algorithm and the animation techniques possible with it to vector fields over curvilinear surfaces, such as those found in computational fluid dynamics simulations. Secondly we introduce a technique to visualize vector magnitude as well as vector direction, i.e., variable-speed flow animation. Thirdly we show how to modify LIC to visualize unsteady (time dependent) flows. Our implementation utilizes texture-mapping hardware to run in real time, which allows our algorithms to be included in interactive applications.>

Line integral convolution (LIC), introduced by B. Cabral and C. Leedom (1993), is a powerful technique for imaging and animating vector fields. We extend the LIC paradigm in three ways: the existing technique is limited to vector fields over a regular Cartesian grid and we extend it to vector fields over parametric surfaces, specifically those found in curvilinear grids, used in computational fluid dynamics simulations; periodic motion filters can be used to animate the flow visualization, but when the flow lies on a parametric surface, the motion appears misleading, and we explain why this problem arises and show how to adjust the LIC algorithm to handle it; we introduce a technique to visualize vector magnitude as well as vector direction, which is based on varying the frequency of the filter function and we develop a different technique based on kernel phase shifts which we have found to show substantially better results. Implementation of these algorithms utilizes texture-mapping hardware to run in real time, which allows them to be included in interactive applications.>