REGULAR PAPER Erhan Okuyan • Ug ˘ur Gu ¨du ¨ kbay • Veysi I ˙ s ¸ler Dynamic view-dependent visualization of unstructured tetrahedral volumetric meshes Received: 27 June 2011 / Accepted: 8 December 2011 / Published online: 11 January 2012 Ó The Visualization Society of Japan 2012 Abstract Visualization of large volumetric datasets has always been an important problem. Due to the high computational requirements of volume-rendering techniques, achieving interactive rates is a real challenge. We present a selective refinement scheme that dynamically refines the mesh according to the camera parameters. This scheme automatically determines the impact of different parts of the mesh on the output image and refines the mesh accordingly, without needing any user input. The view-dependent refinement scheme uses a progressive mesh representation that is based on an edge collapse-based tetrahedral mesh simplification algorithm. We tested our view-dependent refinement framework on an existing state-of-the- art volume renderer. Thanks to low overhead dynamic view-dependent refinement, we achieve interactive frame rates for rendering common datasets at decent image resolutions. Keywords Volume visualization  Direct volume rendering  View-dependent refinement  Progressive meshes  Unstructured tetrahedral meshes 1 Introduction Visualization of large volumetric datasets is an important and challenging area. We focus on the view- dependent refinement of unstructured tetrahedral meshes, widely used in computational fluid dynamics. A representation to store the volume data that allows progressive refinement is crucial for this purpose. A good decimation algorithm is an important factor in constructing the levels of detail (LODs) of the original mesh to obtain a progressive representation. With a progressive mesh representation, the mesh should be refined during runtime in a view-dependent fashion. Electronic supplementary material The online version of this article (doi:10.1007/s12650-011-0122-x) contains supplementary material, which is available to authorized users. E. Okuyan  U. Gu ¨du ¨kbay (&) Department of Computer Engineering, Bilkent University, Bilkent, 06800 Ankara, Turkey E-mail: gudukbay@cs.bilkent.edu.tr Tel.: ?90-312-2901386 Fax: ?90-312-2664047 E. Okuyan E-mail: okuyan@cs.bilkent.edu.tr V. I ˙ s ¸ler Department of Computer Engineering, Middle East Technical University (METU), 06531 Ankara, Turkey E-mail: isler@ceng.metu.edu.tr Tel.: ?90-312-2105591 Fax: ?90-312-2105544 J Vis (2012) 15:167–178 DOI 10.1007/s12650-011-0122-x