Presented at the Eurographics Graphics and Visualization Education
(Maastricht, The Netherlands, August 28-9, 1995)
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
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
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
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?
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.
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.
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
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
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)
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].
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
[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.