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This paper explores two general methods for incorporating volumetric uncertainty information in direct volume rendering. The goal is to produce volume rendered images that depict regions of high (or low) uncertainty in the data. The first method involves incorporating the uncertainty information directly into the volume rendering equation. The second method involves post-processing information of volume rendered images to composite uncertainty information. We present some initial findings on what mappings provide qualitatively satisfactory results and what mappings do not. Results are considered satisfactory if the user can identify regions of high or low uncertainty in the rendered image. We also discuss the advantages and disadvantages of both approaches.

The use of visualization is to convey information in a relatively quick way. To this extent, it is important to convey the most accurate truth about the information, including error and uncertainty so the user can more fully understand the data. In this paper, methods of conveying uncertainty in volume rendering is investigated. There are two approaches to expressing uncertainty in volume rendering presented here: inline and post-process. In the inline approach, the original data is mapped to color, and the uncertainty is mapped to opacity, thus including the uncertainty information into the volume rendering equation. The post-process approach uses discontinuity to express uncertainty in the form of adding speckles (or holes), noise, or texture to the areas of high uncertainty. In both methods, the mapping of uncertainty can be modified depending on the data to be visualized, thus high or low contrast/opacity etc can be mapped to high or low uncertainty. The advantage of the inline approach is that the uncertainty information is integrated into the rendering equation, allowing the information to interact with the data and giving a more faithful representation of uncertainty. The post-processing approach is advantages in that it more intuitively shows the areas of uncertainty, since the eye is quickly drawn to the discontinuities, however the speckles/noise/texture is really just an embellishment on the volume rendering of the data.

volume rendering, transfer functions, opacity mapping, color mapping, speckles, noise, texture

color and opacity mapping, discontinuity via adding speckles/holes, adding noise, and adding texture mapping by varying texture contrast with uncertainty

@InProceedings{	djurcilov:2001:VRUI,
author =	"Suzana Djurcilov and Kwansik Kim and Pierre F. J. Lermusiaux and Alex Pang",
title =	"Volume Rendering Data with Uncertainty Information",
booktitle =	"Data Visualization (proceedings of the EG+IEEE VisSym)",
pages =	"243--52",
year =	"2001",
}