Trial-and-error interface for transfer function specification in direct volume rendering: A user study

Visualization via direct volume rendering is a very powerful technique for researchers to explore and interact with scientific data. However, the complexity of specifying a suitable transfer function (TF) for a specific data set causes many usability problems in the interaction process. The problems are such that they discourage the wider use of volume rendering. This paper presents an overview of important usability issues in the TF specification process, in order to derive an experiment in which some of these issues can be studied in a controlled way. More specifically, the experiment that we describe compares the user performance of some representative interfaces for TF specification. The experimental results have been analyzed from an engineering psychology point of view. The working memory has been identified as the core perception factor which has strong effects on the usability of TF specification. This is an important guideline for designers of such interfaces, and also suggests further questions that we intend to investigate in future experiments.