One method of doing this is to describe particular three-dimensional objects and compare the elapsed time when using SuperSketch to that required when using other systems. Figure 4.16(a), for instance, shows a typical industrial casting. Figure 4.16(b) shows a SuperSketch model of it; the time required to enter this model into the computer was 23 minutes--far less than when using other, more traditional CAD systems. Such comparisons, however, suffer from inequities in raw computer power, operator experience, and the particulars of the three-dimensional shape chosen.
Another way to evaluate SuperSketch is to compare it to more traditional media. Because clay is traditionally the fastest three-dimensional "roughing-in" medium, we have chosen to compare modeling a form in clay to modeling a form using SuperSketch. Figure 4.17 shows two comparisons between modeling using clay and modeling using SuperSketch.
It took a skilled (but non-artist) operator of SuperSketch five minutes to assemble the chair in Figure 4.17(a), and twenty-eight minutes to make the image in Figure 4.17(b). Much of this speed is due to the brevity of the final descriptions: to build the scene in Figure 4.17(b) for instance, requires positioning the mouse fewer than 100 times. These same forms were then modeled in clay (by a different subject). It required four and one-half minutes for Figure 4.17(c) and nineteen and one-half minutes for Figure 4.17(d).
Thus on these two evaluation tasks the SuperSketch system performed with approximately the agility of modeling in clay. This result stands in considerable contrast to performance using traditional three- dimensional modeling systems, which might require many hours to build up a complex form such as shown in Figure 4.17(b). We believe that these comparisons illustrate how the close match between this representational system and people's perceptual organization may be able to facilitate the early "sketching" stages three-dimensional design.
To support our reasoning abilities, perception must recover environmental regularities--for example, rigidity, "objectness," axes of symmetry--for later use in cognitive processes. Understanding this recovery of structure is critically important because the structural organization that perception delivers to cognition is the foundation upon which we construct our picture of the world; these regularities are the building blocks of all cognitive activities.
To create a theory of how our perceptual apparatus can produce meaningful cognitive building blocks from an array of image intensities