Faan Tone Liu
The assignment is to reproduce one of several choices of optical illusions. Part 1 of the assignment requires only loops, while part 2 requires nested loops. Students are asked to modify the image in some (possibly small) way.
Students and instructors find the images themselves interesting and surprising. So the assignment is fun for the students to do.
We don't give starter code or instructions on how to draw the images, as the visual problem solving is part of the fun of the assignment. However, the task is scaffolded by previous assignments in which they have drawn images and animations using loops.
What is unusual about the assignment is that it can be given very early in CS1 (after 2-3 weeks for part 1, after 3-4 weeks for part 2). Students must already be familiar with a basic graphics package, variables, and loops. Two of the options require them to be familiar with animation.
We give multiple options of images for the students to reproduce. The students choose their own level of challenge. We see the more advanced students choosing a more difficult option and taking the assignment to a higher level (especially if offered even a nominal point bonus). The easiest choice is accessible to essentially all of the students.
| Summary | Create an optical illusion using a graphics primitive package, choosing from several options of increasing difficulty |
| Topics |
A visually exciting application of for-loops and nested for loops, variables, and using graphics primitives |
| Audience |
Appropriate at end of first 3 or 4 weeks of CS1
course. |
| Difficulty and length |
Since students may self-select which image to recreate, the assignment provides a high degree of differentiation of difficulty. The first image is easy to create, some of the later ones are difficult. We assign this as one of our weekly projects, with concurrent additional homework. The easiest choice of images can be done by most students in an hour, but students that get involved in and excited by the project can elect to spend many hours reproducing several of the images or animations. |
| Strengths |
One strength of this assignment is that students find the images exciting and interesting. Another strength is that this cool assignment can be successfully completed very early in a CS1 course. A third strength is that there is a wide variety of difficulty to appeal to and challenge the broad range of abilities we see in a first programming course. |
| Weaknesses |
The students must have some experience with a drawing package that includes simple graphics primitives, possibly including animation.
|
| Dependencies |
Students must have competence with variables, assignment, loops and nested loops. |
| Variants |
The instructor can include or omit images based on capabilities of their graphics packages, and based on the difficulty they want to present to their students. The assignment applies to any programming language used, provided the students are familiar with a basic graphics package. Students could create illusions of their own. I'd love to see instructors or students share their own creations to add to the assignment options. |
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Change drawing color Draw narrow line segment (or narrow filled rectangle) Draw filled rectangle |
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Change drawing color Change line width Draw circle outline Draw square outline |
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Change drawing color Draw line segment Students know enough trigonometry to draw a ray (or your graphics package has a ray function) |
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Change drawing color Draw line segment Students know enough trigonometry to draw a polar ray (or your graphics package has a ray function Draw circle outline Draw square outline |
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Change drawing color Draw sector Change line width Draw sector of circle |
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Change drawing color Change background color (or draw filled rectangle to cover background) Change line width Draw line segments (or narrow filled rectangle) Draw filled circle |
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Change drawing color Change background color (or draw filled rectangle to cover background) Change line width Draw line segment Students know enough trigonometry to draw a part of a polar ray Change line width Draw circle outline |
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Change drawing color Change line width Draw line segment Draw filled rectangle |
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Change drawing color Change line width Draw line segment Draw filled rectangle |
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Change drawing color Use image as a background Either edit your image in a photo editor to brighten it Or if your graphics package allows you to get and modify colors of pixels, then modify the background in the program Draw filled rectangle |
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Change drawing color Draw narrow line segment (or narrow filled rectangle) Draw filled rectangle Animation |
| Change drawing color Draw filled rectangle Animation |