The scientific and medical communities are deeply divided over the merit of incorporating artistic devices and photorealism into data visualizations. Techniques such as metallic shading, shadow-casting, surface and solid texturing, and selective defocusing are common in hand-drawn illustrations, but their use in computer-mediated data exploration is not widely accepted. I will argue that these techniques, if properly used, improve spatial comprehension and hence the utility of computer-generated visualizations. To illustrate my argument, I will describe the application of volume rendering - a technique for displaying sampled 3D data - to two problems: 1) interpretation of molecular electron density maps; and 2) planning of radiotherapy for cancer patients.