Spring 1999 CS302 Assignment #2

by Dan Garcia `(ddgarcia@cs.berkeley.edu)`

2. Identify the three concepts or techniques in your course that you expect to be the most difficult for students to learn. Explain why these three things should cause students trouble

1. The "taking a drink from a firehose" rapid-fire intro to Unix / Emacs / Pine / WWW / Quicktime
In an effort to quickly get up to speed with the animation tools, we have reduced the class time devoted to holding their hands and easing them into some of the principal tools. It is hoped that a very detailed handout (as well as lots of lab TA hours) will serve the purpose of getting them up to speed. We hope to emphasize that we are not expecting mastery of these tools, just passing performance (sending / receiving email, searching the www, editing a file, modifying a www template, etc). Still, we expect the sheer breadth and amount of homework we are assigning the first week (these tools and the flipbook) to overwhelm a lot of students. Especially vulnerable are those students who have never touched computers / email / the web before.
2. Basic 3D concepts and spatial ability
We expect many students will not have had much experience in three dimensions, save perhaps the occasional volume calculation in first year calculus, if that. For this group, the transition to three dimensions can be very difficult, especially for those lacking natural spatially intuition. Simple tasks that most of us take for granted (which block is in front of the other, positioning geometry in some arbitrary orientation and point in space) are very difficult for some. In fact, block counting problems are often posed on intelligence tests. It has the potential for bringing up lots of hidden anxieties about spatial reasoning deficiencies. We address this by pairing students up and beginning slowly, e.g. students first design an articulated figure on paper before they ever touch a 3D program.
3. Inferring 3D from 2D projections
Easily one of the hardest things for students is orienting themselves in the virtual 3D world by simply looking through several (top / front / side) orthogonal projections. Many many students just position their characters to look good from one camera position, but sometimes their body parts aren't even connected! They appear connected through just the perspective camera window, and they ignore the fact that the objects just aren't properly connected in the other windows. This can be attributed to a lack of understanding of the concept of 3D - in their mind, the camera is just a way to look at a 2D world, so if it looks good on the camera, it must be ok. They're oblivious to the fact that this static character can never move (because the arm isn't even connected!).

There are also some subtle differences between zooming (changing the focal length) and dollying (moving the virtual camera) that students always misunderstand. This is due to the fact that small modifications can achieve roughly the same effect. However, when they want to bring the character closer, they often simply choose the zoom control (because in their mind they want to zoom closer when in reality they want to move closer) and zoom in, completely distorting the perspective. A lack of experience with photography can also be to blame. Folks who own a SLR with a zoom lens almost never have confusion here.

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