This can be a costly operation. When the data is arranged according to its three-dimensional coordinates, calculating the contour surfaces requires examining each data cell. Avoiding this inherently slow traversal of the entire data set is one of the primary goals of this paper. Real-time rendering of iso-contour surfaces is problematic for large complex data sets. In this paper, an algorithm is presented that allows very rapid representation of an interval set surrounding a iso-contour surface. The algorithm draws upon three main ideas. A fast indexing scheme is used to select only those data points near the contour surface. Hardware assisted splatting is then employed on these data points to produce a volume rendering of the interval set. Finally, by shifting a small window through the indexing scheme or data space, animated volumes are produced showing the changing contour values. In addition to allowing fast selection and rendering of the data, the indexing scheme allows a much com...