Presented at the Eurographics Graphics and Visualization Education Workshop
(Maastricht, The Netherlands, August 28-9, 1995)

Abstract

Student learning and the depth of the student's knowledge increases when active learning methods are employed in the classroom. Active learning strategies are discussed in general computer science course work and as applicable in the graphics class. Difficulties with active learning and techniques for dealing with these are also presented.

1. Introduction

Active learning [Bon91] gets students involved in an activity in the classroom rather than passively listening to a lecture. This activity can be reading, writing, discussing or solving a problem. This is important, because student concentration declines after 10-15 minutes in a 50 minute lecture ([Stu78]).

Further, the act of learning is not passive. As faculty, we learn actively. In preparing lecture notes, we read, possibly from many sources, compare what we have read with our experiences, synthesize the information into coherent notes, and develop examples that illustrate the concept. This leads to greater understanding of the material. Unfortunately, we then use this understanding to lecture to our students depriving them of this journey of discovery. By carefully involving the students in this journey to knowledge, we can increase student depth of understanding of the material, increase student comfort with the material, and improve student confidence. In most sciences, the value of active learning is already realized and implemented through laboratories, or in computer science, through programming projects. The ideas present here are to expand this to include activities in the classroom that replace the lecture or part of it.

If active learning is so successful, why is it not used more frequently? This is because there is a perception that active learning has higher risks. There is fear that content will have to be taken out to put active learning in, that pre-class preparation time is higher, and that active learning is not appropriate for large classes. Perhaps the largest fear is giving up control of the classroom -- a lecture lets the professor decide what to say when, where student centered activities may raise questions that the professor is not ready to answer.

These fears are real, but surmountable. To cover the content, give students the responsibility for learning the factual material so that they can apply it in the classroom discussion. I have had students write on course evaluations that they didn't need to read the book before class because my lecture would tell them what they needed to know from the chapter.

For faculty that re-use class notes year after year, developing active learning strategies will take more time than pulling notes out of a filing cabinet. In a field as rapidly changing as computer graphics, notes need to be done frequently enough that this should not be a concern. Further, as you develop ideas for active learning, you will find that they can be applied across a number of different courses.

Active learning strategies allow you to control the level of risk. By selecting short, highly structured and well-planned activities, the level of risk is fairly low. Involving students by asking a series of questions about the current topic allows the teacher to control the direction and content of the discussion but still makes students active. Breaking the students into small groups, and letting them independently solve a problem is a much higher risk but can prove to be highly rewarding.

2. Active Learning in Computer Graphics

As mentioned above, strategies for the computer graphics classroom are equally valid in many other computer science courses. The strategies will be described generically and examples for the graphics classroom will be given.

Modified Lecture ([Bon91])

As was mentioned, student attention begins to decline after 10-15 minutes of lecture. Further, we have all been in lectures where something catches our attention, causing us to "miss" part or all of the next point. A low risk strategy to handle both of these is to lecture for 10-13 minutes and then take a 2-3 minute "break." During the break, students can discuss their notes with the person next to them filling in gaps and correcting misunderstandings. Alternatively, an activity that leads to a discussion would be to pose a question and then employ the "think-pair-share" technique. In this technique, a question is posed to the students who then individually write an answer within a one to two minute time limit. Students then "pair" up and discuss their answers, possibly developing a new answer. The instructor can then lead the class into a discussion or the next lecture topic by asking a few pairs to "share" their answer with the class.

In the graphics class, you could pose questions like:

What will happen to the highlights on this ball if we increase the coefficient of reflection?

How will this shadow change if the light source moves closer?

Why is it important to reduce the number of multiplications and divisions in graphics (or line drawing) algorithms?

Algorithm Tracing

Instead of tracing the execution of an algorithm in a lecture, break the students into groups and have them trace the algorithm. For example, to compare the DDA and Bresenham algorithms for lines (or circles) break up the class into groups of four students each. Assign one student as the algorithm tracer, one to keep track of the variable values, another to record the number of additions/multiplications performed, and the last to record the visual output. By providing each team with transparencies (with permanent grids) and markers, teams can compare the results of the two algorithms, and easily display their answers to the rest of the class.

Physical Experimentation

To understand computer graphics, one must understand the physical processes that it is stimulating. Though we look at things all the time, we do not tend to carefully look and analyze what we are seeing. This is probably especially true of students and probably much less true of computer graphics faculty. My attention will be captivated by light and shadows that are cast on a wall if the light source is not obvious. I find myself mesmerized by the relative positions of objects, shadows, lights, and reflective surface as I try to figure the complex path the light might be taking. The same is true of many other lighting effects.

Instead of explaining how lighting works, it would be more instructive to describe the types of reflections and refractions and then provide the students with flashlights (torches) and different types of objects and let them try to recreate the effects. This type of exercise is especially important because it will also get the student to begin visualizing particular effects and critically analyzing physical and computer generated images.

Demonstration Software

Dino Schweitzer [Sch92] has developed a series of demonstration programs that can be used in the classroom and are available through the ACM SIGGRAPH Computer Graphics Courseware Repository (via ftp from cgcr.gsu.edu, login:cgcr, password:cgcr or via http://education.siggraph.org). The topics covered include line clipping, color maps, boundary fill algorithm, line drawing, shading, 2-D and 3-D transformations and projections.

G. Scott Owen [Owe92] has developed a system called "Hyper Graph" that is a hypermedia system he uses in place of a graphics textbook. This system includes not only written descriptions but also images and animations that the user can interact with.

In a classroom with a projection unit connected to a computer system running demonstration software, the professor has a powerful tool to have students interact with the ideas of computer graphics. By dividing the students into groups, you can ask them to predict what will happen to an image based on some process (e.g. scale followed by a rotation) or ask them what is necessary to cause a particular effect (e.g. shadow an object by repositioning a light source).

This set up also allows students to formulate "what if" questions as they are trying to understand an idea. For example, students trying to understand the rendering equation, with the proper software, can alter parameters and watch as the object(s) change appearance.

3. Active Learning Examples

The examples of student centered learning presented below represent the full inclusion of active learning concepts and minimize lecture time. These classes take preparation time that is different from that for a pure lecture. In the fall, 1995 semester, I will be teaching three courses using active learning, each having a slightly different structure. A computer graphics course could use adaptations of these forms.

In my "Theory of Computation" course, students will be broken into groups that will stay fixed for the entire 14 week semester. I will decide the composition of the groups. (For information on group work see [Fei85].) The students will need to learn how to work together, in spite of their differences, much as they will in professional settings after college. Each 75 minute class will begin with a 15 minute mini-lecture with an example problem solved. The students will then work for 20 minutes in groups on one or two problems posed to them. There will then be a second mini-lecture and problem session. The class will end with a brief wrap up, and groups will turn in their problem session answers for grading. There will be three term exams that the students will first work on individually and then afterward work as a group, earning two grades for each exam. To encourage the groups to work together to all learn the material equally well, there will be a bonus if all member's grades are within some threshold (e.g. 10%) of the group exam grade. In the past, this structure has been very effective in increased learning by students not only at the bottom of the class, but the top as well [McC95].

The second course, "Analysis of Algorithms," will begin with the students developing a list of questions that they had from the reading. They will then need to rank this in the order they want me to answer them. The questions must be more specific than "explain X." This process is allocated no more than 10 minutes. I will then answer as many questions as possible in the next 30 minutes (or less). For the remaining 35 minutes of the class, the students will work on a problem set, with answers turned in at the end of class. There will be two examinations structured as in the "Theory of Computation" course.

The last course, "UNIX and C," meets once a week for fourteen weeks. In this course, each class will begin with a short (10 minute) group session for the students to clear up any questions. The next 10 minutes will be a true/false and multiple choice quiz on the reading material. Students will next work individually on a programming exercise while I grade the quizzes (about 10 minutes). The quizzes will be returned and students will then form their groups to finish work on the exercise. The resulting program will be due the following week. There will be no midterm exams; however, all students will need to successfully complete a mastery exam at the end of the course, to show competence in the course material. (It should be noted that exam scanning equipment exists, that allows this structure to be used in large classes.) A colleague of mine, Frank Dinan, has successfully used a structure similar to this for his organic chemistry course [Din95].

Conclusion

Adopting active learning techniques can be risky for faculty, but the risk can be minimized. As your comfort level with active learning increases, riskier strategies can be tried. Though the loss of control can be scary at first, I have found myself invigorated and look forward to the challenge of the active learning.

The reality of today's higher education in the United States is that students do not seem to be as interested in learning as they once were. By employing active learning strategies, students not only learn content, but process as well. This makes them better students in later courses, and better professionals after finishing their degree.

References

[Bon91] Charles C. Bonwell and James A. Eison. Active Learning: Creating Excitement in the Classroom., ASHE ERIC Higher Education Report No. 1, Washington, D.C.: The George Washington University, School of Education & Human Development, 1991.

[Din95] Frank J. Dinan and Valerie A. Frydrychowski, "A Team Learning Method for Organic Chemistry," Journal of Chemical Education, Vol. 72, pp. 429-431, May, 1995.

[Fei85] Susan Brown Feichtner and Elaine Actis Davis. "Why Some Groups Fail: a survey of students' experiences with learning groups." Organizational Behavioral Teaching Review, Vol. 9, pp. 58-73, 1985.

[McC95] Jeffrey J. McConnell, "Active Learning and Group Work in a Theory of Computation Course," submitted to the 27th SIGSCE Symposium on Computer Science Education.

[Owe92] G. Scott Owen, "HyperGraph - A Hypermedia System for Computer Graphics Education." In Interactive Learning Through Visualization, S. Cunningham, and R. J. Hubbold (eds), Springer-Verlag, Berlin, 1992.

[Sch92] Dino Schweitzer, "Designing Interactive Visualization Tools for the Graphics Classroom." In the Proceedings of the Twenty-third SIGCSE Technical Symposium on Computer Science Education, Kansas City, Missouri, March 5-6, 1992, pp. 299-303.

[Stu78] John Stuart, and R. J. Rutherford, "Medical Student Concentration During Lectures." The Lancet, Vol. 2, pp. 514-516, September 1978.