Suppose the World was Piecewise Plastic?

Chuck Hansen

(Utah)


Is it ridiculous to think of the world has nothing but plastic? That
is precisely an assumption most volume renders make by using the Phong
illumination model.

Direct volume rendering has proven to be an effective and flexible
visualization method for interactive exploration and analysis of 3D
scalar fields. While widely used, most if not all applications render
(semi-transparent) surfaces lit by an approximation to the Phong local
surface shading model. This model renders surfaces simplistically (as
plastic objects) and does not provide sufficient lighting information
for good spatial acuity. In fact, the constant ambient term leads to
misperception of information that limits the effectiveness of
visualizations. Furthermore, the Phong shading model was developed for
surfaces, not volumes. The model does not work well for volumetric
media where sub-surface scattering dominates the visual appearance
(e.g. tissue, bone, marble, and atmospheric phenomena). As a result,
it is easy to miss interesting phenomena during data exploration and
analysis. Worse, these types of materials occur often in modeling and
simulation of the physical world. Physically correct lighting has
been studied in the context of computer graphics where it has been
shown that the transport of light is computationally expensive for
even simple scenes. Yet for visualization, interactivity is necessary
for effective understanding of the underlying data. We seek increased
insight into volumetric data through the use of more faithful
rendering methods that take into consideration the interaction of
light with the volume itself.
Thursday 1st March 2007, 14:00
Robert Recorde Room
Department of Computer Science