Illustrative Context-Preserving Volume Rendering

Stefan Bruckner, Sören Grimm, Armin Kanitsar, M. Eduard Gröller
{bruckner | grimm | kanitsar | groeller}@cg.tuwien.ac.at

Institute of Computer Graphics and Algorithms
Vienna University of Technology, Austria

Abstract

In volume rendering it is very difficult to simultaneously visualize interior and exterior structures while preserving clear shape cues. Very transparent transfer functions produce cluttered images with many overlapping structures, while clipping techniques completely remove possibly important context information. In this paper we present a new model for volume rendering, inspired by techniques from illustration that provides a means of interactively inspecting the interior of a volumetric data set in a feature-driven way which retains context information. The context-preserving volume rendering model uses a function of shading intensity, gradient magnitude, distance to the eye point, and previously accumulated opacity to selectively reduce the opacity in less important data regions. It is controlled by two user-specified parameters. This new method represents an alternative to conventional clipping techniques, shares their easy and intuitive user control, but does not suffer from the drawback of missing context information.

Videos

The following video sequences illustrate some aspects of the method presented in the paper. Further material can be found online. All files are Intel Indeo Video 4.5 encoded AVI videos. If your system does not have this codec installed, you can download it for Windows or MacOS platforms. Indeo playback is also supported by several Linux applications. Note: If you use Windows XP and Windows Media Player, you cannot playback these files from remote locations (such as a network drive) - you have to save them on your local hard disk.

	Comparing context-preserving volume rendering to conventional direct volume rendering, gradient-magnitude opacity modulation, and direct volume rendering using a clipping plane. The same transfer function is used for all four methods. [AVI] 16.4 MB
	Context-preserving volume rendering of a human hand CT data set. [AVI] 42.3 MB
	Context-preserving volume rendering of the visible human male CT data set. [AVI] 64.7 MB
	Context-preserving volume rendering of a human head CT data set using a modulation function for the model parameters which makes the bone impenetrable. [AVI] 32.1 MB