CSE3313
Computer Graphics

Assignment 1
2D Graphics – Superformula!

Due Date: Friday, 24 August 2007 before 11.59pm.

Marks: 10% of your total mark for this unit.

This assignment is designed to give you some experience in using OpenGL. Although OpenGL is inherently 3D, this assignment will only require you to output 2D primitives for graphical output. You must code your solution in the C or C++ programming languages using OpenGL. This can be done using the Linux PCs.

The superformula is a simple mathematical equation capable of drawing a wide variety of natural shapes. It is a generalisation of the equation for a superelipse. It is given by the following equation:

ni and m are real numbers >= 0, a and b are real numbers > 0. The equation is specified in polar coordinates, returning a radius, r, at a given angle. See the paper in the link above for more details. The shapes shown below are all generated using the superformula. Different shapes are obtained by changing the values of n1, n2, n3, a, b and m.

You can generate superformula in OpenGL by approximating the continuous formula with a series of points to form a closed polygon or line segment.

For this assignment you are required to write a program that generates the superformula in a variety of forms using OpenGL. Interaction with the program will be done via keyboard and mouse commands outlined below. Your program should display three viewports in one window (see diagram below). The first viewport is the main view which contains the main rendering of previously edited superformulas along with the current superformula being edited. The second viewport shows keyboard commands and status, using OpenGL text. The third viewport shows the current superformula primitive being edited. It should be possible to resize the window. Ensure that your program maintains correct aspect ratios if the window is resized.

The basic idea is that individual superformulas are edited in the edit view. Here the user may adjust parameters using keyboard and mouse commands. The current superformula being edited appears in both the main view and the edit view. Once the user is satisfied with the shape, colour and form of the current superformula being edited, they then press the E key, which "freezes" the current parameters and transformations. This superformula object is kept in the main window, but as new superformula object appears in the edit and main views and can now be edited. This way it is possible to build a complex shapes, composed of any number of superformula objects, which are all displayed in the main view.

The text view should show:

• the keyboard commands (listed below)
• values of n1, n2, n3, a, b and m for the superformula being edited and their edit state
• the status of AnimateMode, FillState and RotateMode
• the total number of superformula objects in the main view

Keyboard Interaction

Your program should support the following keyboard commands:

Use sensible values for the default translation amount, the default scale increase and decrease factors, rotational velocity, etc. (they should be the same for each direction). The program needs to update the viewports immediately in response to any changes.

Programming Tips

• Develop a data-structure to represent a superformula object and its associated parameters.
• You can use display lists to store the edited formulas and thus increase drawing speed.
• Handle all transformations with OpenGL calls – there is no need to calculate transformations explicitly (e.g. using trigonometry).
• Make sure you allow time for adequate testing. Test your program on ra-clay as this is the machine it will be assessed on.
• Don't have repeated code blocks — factorise into functions (C) or classes (C++). Avoid large numbers of global variables – put related variables into compound data structures.
• The user should be allowed to resize the display window — don't forget to adjust aspect ratios when this happens.
• Don't take any illegal drugs while watching the superformula patterns rotate.

Submission

You need to submit your program for assessment in electronic form using the submit program. See the submit page for details on how to submit assignments. You should submit a directory which contains the following:

1. source code (.c, .cpp and .h files — see the declaration that must be included with all source files)
2. a Makefile with the correct targets
3. a plain text README file that describes how to run the program (including any command line options) and a brief description of how you coded your solution (no more than 1 A4 page of text).

Do not submit any other files. Submissions that fail to make or compile will not achieve a passing mark, nor will a program that does not run.

Marking Criteria

The following criteria will be used when assessing your submission:

• Submission of working code, correct Makefile, descriptive README in plain text (i.e. not pdf, .doc, etc.);
• Style of programming: conciseness, comments, adherence to good OO (C++) or imperative (C) programming principles;
• Quality, efficiency and readability of the solution and algorithms used;
• Efficient and appropriate use of OpenGL (e.g. Viewports, transformations, display lists, text, appropriate primitives, etc.);
• Correct implementation of the features specified;
• Submission by the due date.