BU CAS CS 480

Introduction to Computer Graphics

Spring 1996

Programming Assignment 1

Due before class on Tuesday, February 6

The polygon editing tool must run on the SGI, therefore you will need to use one of the SGI workstations in the CGL cluster (unless you have access to an SGI workstation elsewhere).

Your program's source files are to be electronically submitted by using the submit program on cgl. The code you submit should conform with the program assignment guidelines.

Part of your grade for this programming assignment will be based on your giving a short demo (2-3 minutes) in the CGL cluster. You will be expected to talk about how your program works, and we will see how well your program performs on some test examples. A demo date for this assignment is not yet scheduled but will be announced in class this Thursday, January 30. You will be asked to sign up for a slot by next Thursday.

Start programming early.

Get Some Files

• poly.c the polygon drawing main program
• callbacks.c routines invoked by the event handler
• Makefile an example make file
• wire.c , fill.c code templates for the two subroutines you write
• const.h , types.h , func.h header files

By copying the source files, you have almost everything you'll need to build your own polygon drawing program. You are expected to complete the program by providing two missing subroutines using the code templates and by adding new callbacks. There are comments in the two template files that will help guide you in writing your own subroutines.

Example Program

The Code You Write

• In wire.c write a subroutine that calls the appropriate OpenGL routines to first draw a closed polygon's edges in the edge color, and then draw the polygons's points in the point color. If there are more than two points, then the polygon should be drawn closed.

• In fill.c write a modified scan-line polygon fill subroutine based on the algorithm described in the text on pages 117-125. Rather than scan-converting the polygon, your subroutine should generate a series of quadrilaterals and triangles as described in class, and as illustrated in the fill.c code template.

• Add the following new functionality to your program
  1. Setup keyboard control for: increasing and decreasing line width (suggestion, use arrow keys for input control).

  2. Setup up keyboard control for toggling of OpenGL antialiasing.

  3. Change the colors used in your program to suit your own taste while also satisfying visibility constraints.

Extra Credit

The user should be able to toggle texture mapping on and off by using the T key.

It possible to make the texture stretch as you pull the polygon, or to make it stay fixed. It depends on what values you send into the CS480 class Home Page for links to online OpenGL documentation. The following is a partial list of OpenGL routines you will probably need to do the compulsory part of this assignment:

• glBegin
• glClearColor
• glClear
• glColor
• glFlush
• glGetIntegerv
• glLoadIdentity
• glMatrixMode
• gluOrtho2D
• glPointSize
• glVertex
• glViewport
• glXSwapBuffers

Hint 2: Example OpenGL Programs

Hint 3:

Page Created: Jan 20, 1996      
Last Modified: Jan 11, 1996
Maintained by: Stan Sclaroff