Scalable hybrid unstructured and structured grid raycasting

Philipp Muigg*, Markus Hadwiger, Helmut Doleisch, Helwig Hauser

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


This paper presents a scalable framework for real-time raycasting of large unstructured volumes that employs a hybrid bricking approach. It adaptively combines original unstructured bricks in important (focus) regions, with structured bricks that are resampled on demand in less important (context) regions. The basis of this focus+context approach is interactive specification of a scalar degree of interest (DOI) function. Thus, rendering always considers two volumes simultaneously: a scalar data volume, and the current DOI volume. The crucial problem of visibility sorting is solved by raycasting individual bricks and compositing in visibility order from front to back. In order to minimize visual errors at the grid boundary, it is always rendered accurately, even for resampled bricks. A variety of different rendering modes can be combined, including contour enhancement. Avery important property of our approach is that it supports a variety of cell types natively, i.e., it is not constrained to tetrahedral grids, even when interpolation within cells is used. Moreover, our framework can handle multi-variate data, e.g., multiple scalar channels such as temperature or pressure, as well as time-dependent data. The combination of unstructured and structured bricks with different quality characteristics such as the type of interpolation or resampling resolution in conjunction with custom texture memory management yields a very scalable system.

Original languageEnglish (US)
Pages (from-to)1592-1599
Number of pages8
JournalIEEE Transactions on Visualization and Computer Graphics
Issue number6
StatePublished - Nov 2007
Externally publishedYes


  • Focus+context techniques
  • Hardware-assisted volume rendering
  • Volume rendering of unstructured grids

ASJC Scopus subject areas

  • Software
  • Signal Processing
  • Computer Vision and Pattern Recognition
  • Computer Graphics and Computer-Aided Design


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