Explorable images for visualizing volume data

We present a technique which automatically converts a small number of single-view volume rendered images of the same 3D data set into a compact representation of that data set. This representation is a multi-layered image, or an explorable image, which enables interactive exploration of volume data in transfer function space without accessing the original data. We achieve this by automatically extracting layers depicted in composited images. The layers can then be recombined in different ways to simulate opacity changes and recoloring of individual features. Our results demonstrate that explorable images are especially useful when the volume data is too large for interactive exploration, takes too long to render due to the underlying mesh structure or desired shading effect, or if the original volume data is not available. Explorable images can offer real-time image-based interaction as a preview mechanism for remote visualization or visualization of large volume data on low-end hardware, within a mobile device, or a Web browser.