A Magnification Lens for Interactive Volume Visualization

Volume visualization of large data sets suffers from the same problem that many other visualization modalities suffer from: either one can visualize the entire data set and loose small details or visualize a small region and loose the context. In this paper, we present a magnification lens technique for volume visualization. While the notion of a magnification-lens is not new, and other techniques attempt to simulate the physical properties of a magnifying lens, our contribution is in developing a magnification lens that is fast, can be implemented using a fairly small software overhead, and has a natural, intuitive appearance. The issue with magnification lens is the border, or transition, region. The lens center and exterior have a constant zoom factor, and are simple to render. It is the border region that blends between the external and interior magnification, and has a nonconstant magnification. We use the “perspectivecorrect textures” capability, available in most current graphics systems, to produce a lens with a tessellated border region that approximates linear compression with respect to the radius of the magnification lens. We discuss how a “cubic” border can mitigate the discontinuities resulting from the use of a linear function, without significant performance loss. We discuss various issues concerning development of a three-dimensional magnification lens.