CS 551/645: Introduction to Computer Graphics

Goal: Hello World program to get you started. You will learn how to use Xforms, Makefiles, and Unix in general.

Assigned: Wednesday, September 8, 1999

Due: Monday, September 13, 1999

Relevant reading/files/software:

• The class web page (http://www.cs.virginia.edu/~cs551) has pointers to getting your UNIX account set up correctly.
• We will be using the Xforms GUI-building package: http://bragg.phys.uwm.edu/xforms
• We will also use OpenGL (http://www.opengl.org) or the public-domain implementation of OpenGL called Mesa: http://www.mesa3d.org. However, you will not need to know any details for this assignment

Synopsis: A simple "Hello World" sort of program. We will provide source code for a function that, given an OpenGL context, draws a simple scene (either a cube or icosohedron, depending on which function it calls). You will need to design a form in fdesign that contains:

• An OpenGL canvas in which to display the object.
• Controls for changing the background color of the canvas (at the simplest, buttons to make the background color red, green, or blue).
• Controls for rotating the object incrementally (at the simplest, a "Rotate left" and "Rotate right" button).
• A "Quit" button.

Doing all of this will earn you an 8/10. To earn extra points, you will want to implement some "bells and whistles". There are many possible extras that could be added, such as:

• Better controls for rotation, or rotation around more than one axis.
• Sliders to control red, green, and blue values for the background color exactly.

These are just two very simple examples; you should be able to think of many more on your own. As usual, the single best assignment will earn a 10.

Turning in the assignment: Before class starts on Monday, September 13, you should:

• Verify that the line in your Makefile beginning "SUBMIT =" includes all relevant files: source code (including header files!), fdesign form files (.fd suffix), and Makefile itself.
• Type "make submit" in the directory containing your code. You will get mail in return from the CS551 account with a list of the files that were successfully received.
• If you submit the assignment multiple times be aware that we will only see the last attempt.

Specifics: We are providing a Makefile, which contains rules for compiling and submitting programs, and a C file named gfx.c, which contains code to draw into an Xforms glCanvas. You will create a form in fdesign. Saving that form (as a .fd file) will also create .c and .h files that contain the Xforms library code for creating the form, which you must include in your program via the Makefile. Some special things to notice about the code:

• Your code will need to create a global variable pointing to your form. This pointer is returned from the create_form_* call; the Xforms doucmentation has details. To make the code in gfx.c work correctly you must name this variable myForm. Your form must include a glCanvas object, which you must name myCanvas.
• Gfx.c defines some global variables: rot represents the amount of rotation applied to the object drawn by draw_icos() or draw_cube(). The variables BGr, BGg, and BGb store the red, green, and blue components of the background color. By altering these variables, you can affect the behavior of the graphics subroutines without worrying about the code therein.
• Gfx.c contains a function called canvas_expose() which will redraw the canvas when it is created or covered and exposed by another window. After the create_form_* call, you must attach this function to your canvas with the line:
  fl_add_canvas_handler(myForm->myCanvas,Expose,canvas_expose,0);