Volume Rendering
This section desribes a new algorithm for generating preview images of volumetric data sets defined on arbitrary meshes. It was developed by Kwan-Liu Ma and myself as a class project for Prof. Ma's ECS 289H Advanced Volume Visualization class in the Winter quarter of 2000.
I have written an article about this algorithm that has been submitted to (and rejected by) the Volume Visualization '00 conference. The title:
Point-Based Rendering of Arbitrary-Mesh
Volumetric Data at Multiple Levels of Resolution
| Oliver Kreylos | Kwan-Liu Ma | Bernd Hamann |
Abstract
In this paper we describe a rendering method suitable for interactive previewing of large-scale arbitary-mesh volume data sets. A data set to be visualized is represented by a "point cloud," i.e., a set of points and associated data values without known connectivity between the points. The method uses a multi-resolution approach to achieve interactive rendering rates of several frames per second for arbitrarily large data sets. Lower-resolution approximations of an original data set are created by iteratively applying a point-decimation operation to higher-resolution levels. The goal of this method is to provide the user with an interactive navigation and exploration tool to determine good viewpoints and transfer functions to pass on to a high-quality volume renderer that uses a standard algorithm.
This kinda says it all, doesn't it? If not, you can download the complete paper as well. But beware: It is rather large (4.9 MB), due to the lovely page-filling color images.
Visualization Examples
The results of mangling the following data sets with our algorithm can be admired:
- The "Mavriplis" data set
- This data set, resulting from an airflow simulation, was provided by Dimitri Mavriplis at ICASE. It is defined on an unstructured (tetrahedral) grid consisting of 2,800 vertices and 13,576 tetrahedra.
- The "Blunt Fin" data set
- This ubiquitous data set (the "Utah Teapot" of CFD visualization) resulted from an airflow simulation as well. It was provided by C.M. Hung and P.G. Buning. It is defined on a curvilinear hexahedral grid consisting of 40,960 vertices.
- The "Parikh" data set
- This data set, also resulting from an airflow simulation, was provided by Paresh Parikh at ViGYAN, Inc. It is defined on an unstructured (tetrahedral) grid consisting of 103,064 vertices and 567,862 tetrahedra.
- The "Shalf" data set
- This data set, resulting from a cosmological simulation, was provided by Greg Bryan, Mike Norman and John Shalf at the Laboratory for Computational Astrophysics at NCSA and Lawrence Berkeley National Laboratory. It is defined on a hierarchy of rectilinear grids generated by an adaptive mesh refinement (AMR) algorithm. It consists of 2,531,452 vertices altogether.
All of the above pages feature thumbnails of the images in question. The original (large) versions of the images can be downloaded in PNG format by clicking on the thumbnails. Beware: The large images are large (891 x 747 pixels each), and every single one is around 400 KB - they have to be seen in true color, and without the artifacts introduced by JPEG. (All the artifacts you do see in the images are home-made and intended to be there!)