Novel Volume-Visualization Methods for the Interactive Rendering of CFD Simulation Data

Spatial grid data structures, which are the foundation for modern CFD simulations, have become more flexible allowing for efficient simulation techniques but also making the result visualization more difficult. Whereas initially only tetrahedral or block structured grids have been used nowadays simulation tools (e.g. Fluent, Star CD, etc.) use grids which decompose the simulated domain into different types of convex polyhedra. Especially when performing volume rendering most state of the art approaches perform a tetrahedral subdivision of these more complex cells. This can result in ambiguous visualizations since different tetrahedralizations of the cells can be applied. Additionally the number of cells which have to be visualized can increase drastically. We propose a (graphics hardware based) volume rendering approach which copes with large unstructured polyhedral grids in several novel ways:- we perform volume rendering on the original grid (no tetrahedralization is necessary)- we subdivide the grid in order to visualize each part according to its contents and visibility- we support multiple rendering modes in order to emphasize different aspects of the data- we perform resampling of unimportant regions of the volume onto a low resolution structured grid in order to retain interactivity even on standard PC hardware In order to distinguish between important and unimportant regions of the volume a so called Degree of Interest (DOI) volume is used, which can be specified in the SimVis framework into which our approach has been integrated. We demonstrate the effectiveness of our method by using it to visualize two different CFD simulation cases. Keywords