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-photo by Kartic Subr

Introduction to Computer Graphics- Perception IS Data?
by Kartic Subr
28 July 2003

When does SIGGRAPH start? If you are the conference chair, it starts two years in advance. If you are only coming for the exhibition, SIGGRAPH begins when the Main Exhibition Hall Opens. For those who come early and register for the full conference, the courses provide interesting knowledge and instruction unlike that provided in a paper or classroom. On the opening day of SIGGRAPH 2004, just before virgin SIGGRAPH attendees were overwhelmed by all the technology, art and stunning research, Michael Bailey drew the audience's attention with his quote "Perception is data". That raises a very important point- do we finally want to display what IS, or what makes us perceive the "IS" ?

An Initiation

The "Introduction to Computer Graphics" course appeared to be a popular venue on the first day of SIGGRAPH '03. CG rookies flocked to rooms 14 A-B at the San Diego Convention Center to attend this course which was organized by Michael Bailey from the San Diego Supercomputer Center.The two lecturers were Bailey and Andrew Glassner, from Coyote Wind Studios The planning committee did well to make this the only course open to all SIGGRAPH attendees.

Starting with an introduction to the graphics process, the two speakers enlightened the audience. The goals of the course were indeed achieved when light was thrown on fundamental concepts in CG such as modeling, rendering and animation. The other sections covered in the course were Graphics Display Hardware and Scientific Visualization. The course was concluded by a crisp and informative "How to Attend SIGGRAPH" session. The day-long course was a good blend of technical details, interesting applications and witty humor.

Scientific Visualization

The conference management staff probably regretted not having planned enough seating for this course and it did not appear to be their fault. This session was educative to the average rookie, touching upon application areas such as medicine, geology and engineering.

Using custom-brewed software that he used in his teaching, Bailey demonstrated effects such as the "Row of Corn", different projection techniques and volume visualization with range sliders to control the opacity.

Perception? Why Bother?

Bailey, in his talk on scientific visualization, mentioned the importance of understanding the way we perceive visualized data."There is a huge range of techniques that we could apply to change the way we perceive data; the first step is to understand them.", he said. He also explained that this was because of the anomalies in the human perception system. As a simple example, he used the traditional Mach bands to support "Our eyes do not see absolute color; only relative color...". Both speakers demonstrated several examples of optical illusions, eliciting a spectrum of responses- from the "Yea, I've seen this one before" smile to "Now you're kidding me!" exclamations.

Although correctness, precision and accuracy are extremely important in Scientific Visualization, if the resulting visualization is going to be perceived and interpreted by a human, should we apply techniques based on our understanding of the human perceptual system that will make interpretation of the data correct? Would this in turn affect the effectiveness of visualization as a tool for data interpretation? Those were some of the questions ringing in the heads of the audience by the end of the talk. The speakers were also kind enough to talk to the long line of people who were asking questions or looking for advice.