Photo- and physically realistic techniques are often insufficient for visualization of fluid flow simulations, especially for 3D and time-varying studies. Substantial research effort has been dedicated to the development of non-photorealistic and illustration-inspired visualization techniques for compact and intuitive presentation of such complex datasets. However, a great deal of work has been reproduced in this field, as many research groups have developed specialized visualization software. Additionally, interoperability between illustrative visualization software is limited due to diverse processing and rendering architectures employed in different studies. In this investigation, a framework for illustrative visualization is proposed, and implemented in MarmotViz, a ParaView plug-in, enabling its use on a variety of computing platforms with various data file formats and mesh geometries. Region-of-interest identification and feature-tracking algorithms incorporated into this tool are described. Implementations of multiple illustrative effect algorithms are also presented to demonstrate the use and flexibility of this framework. By providing an integrated framework for illustrative visualization of CFD data, MarmotViz can serve as a valuable asset for the interpretation of simulations of ever-growing scale. cell centroid of a cell or region (m) distance of contour points from a central axis (m) edge feature graph constructed from mesh thickness for feature halos (m) products of inertia tensor for a region (m5) volumetric angular momentum of a region (m5 s−1) number of unmatched regions-of-interest camera projection plane normal octree used for feature matching point on a contour (m) queue used for feature matching region-of-interest position vector (m) strobe silhouette curve bounding contour around a feature time (s) user-specified threshold velocity of a cell, or volume-average velocity of a region (m s−1) volume of a cell or region (m3) spatial coordinates (m) initial value bounding contour around a feature rear point on a contour cell count threshold for regions-of-interest gradient threshold for regions-of-interest counting indices left-most point on a contour inset contour around a feature minimum/maximum values along a contour offset contour around a feature right-most point on a contour estimated value similarity parameter for feature matching (-) user defined time step (s) similarity criterion for feature matching (-) relaxation parameter for feature matching (-) hard lower limit for the feature matching criterion (-) volumetric average angular velocity of a region (s−1) 
Framework and algorithms for illustrative visualizations of time-varying flows on unstructured meshes