Graphics: Visual and Interactive Computing

The first five images were extracted from a video of a rheological experiment. The other three images represent visualisation of three different geometrical models.

Please also visit the Swansea volume graphics gallery.

This work was conducted jointly by the Computer Graphics and Visualisation group and the Scientific Computation group at Swansea. Although it is not, technically, in the field of volume graphics, we conveniently file this work with our volume graphics projects.

Comparative evaluation of visualization and experiment results is a critical step in computational steering. This work is a study of image comparison metrics for quantifying the level of difference between a visualization of a computer simulation and a photographic image captured from an experiment. We exam-ined eleven metrics, including three spatial domain, four spatial-frequency domain and four HVS (human-vision system) metrics. Among these metrics, a spatial-frequency domain metric called 2nd-order Fourier comparison was proposed specifically for this work. Our study consisted of two stages: a path finding stage and a field trial stage. The former is a general study on a controlled comparison space using purposely selected data, and the latter in-volves imagery results from computational fluid dynamics and a rheological experiment. We considered the effects of typical ren-dering attributes in the comparison, and tested several methods for preprocessing the imagery data, prior to the application of compar-ison metrics.

This study has provided a structured analysis of the suitability of different metrics in a variety of circumstances, and offered a set of informative indicators as to the strengths and weaknesses of each metric. In particular, we have identified three image compari-son metrics that are effective in separating similar and different image groups. Our 2nd-order Fourier comparison metric has per-formed well consistently in different tests, and has shown its poten-tial to be used for steering computer simulations quantitatively and automatically.

Readers may find details of our comparison results in the pages for the path finding stage and the field trial stage, which was not able to be included in our IEEE Visualization paper due to the page limits. We also hope some readers may find the original imagery data useful as a benchmark problem.

Main Reference

• H. Zhou, M. Chen and M. F. Webster, Comparative evaluation of visualization and experimental results using image comparison metrics, to appear in the Proceedings of IEEE Visualization 2002, Boston, Massachusetts, 27 October - 1 November 2002.