Vortex flow visualization using tetrahedral cell subdivision

Proposes an effective technique for searching for critical points, which are points at which the velocity vector is zero. The previous method, using tetrahedral-cell subdivision, often generates multiple critical points in a hexahedral cell, and this causes several defects in flow visualization. First, we propose a new criterion for differences between interpolation functions, and investigate the reasons for the generation of multiple critical points in a hexahedral cell. Next, to prevent the generation of multiple critical points, we propose an improved method using both tetrahedral-cell subdivision and a trilinear interpolation function. Our method finds critical points by using a linear interpolation function, and, when multiple critical points are found in a hexahedral cell, a numerical integration scheme (Newton's method) is applied and a more precise position is calculated. We apply our approach to several sets of velocity data and evaluate it in several ways.