CS 551/645: Introduction to Computer Graphics

Goal: Understand and implement general viewing transformations

Assigned: Wednesday, October 13, 1999

Due: Friday, October 22, 1999

Relevant reading/files/software:

• Foley and van Dam, chapter 5.
• Check the class web page (http://www.cs.virginia.edu/~cs551) and this assignment frequently. We will add any updates in red.
• No resources on the Internet may be consulted. 

Synopsis: You will implement a library (libtransform.a) containing matrix routines for basic 3-D modeling and viewing operations: translation, scale, rotation about X, Y, Z, and an arbitrary axis, and a "look at" operation for setting camera pose.

Specifics: We are providing a header file transform.h defining function prototypes for the library; you will have to fill in the source code for those functions. We will also provide a file gfx.c with functions for rendering simple objects into an XForms glCanvas using a viewing matrix you specify, and a matrix library (matrix.h and matrix.c) with some handy functions which assume row-major matrices. (Makefile was last modified at 3:40PM on Oct 14. matrix.h and transform.h were last modified at 6:40PM on Oct 18. gfx.c last modified at 3:05PM on Oct 21. matrix.c was last modified at 9:20PM on Oct 19.) For debugging purposes, you may wish to modify your demo from Assignment 1 using the new functions. We also provide the usual Makefile. Note:

• All the functions should be self-explanatory except lookat(). This function takes a viewpoint for the camera location, a lookat point that the camera is looking at, and an up vector that specifies what direction should correspond to the +Y axis on the screen.
• You must write the lookat() function using only calls to the other functions in your library. No setting the matrix elements directly in the lookat() function.
• Rotations are specified in a counterclockwise direction for an observer looking down the negative axis of interest. For example, a rotation about the Z-axis rotates counterclockwise for an observer at the origin looking towards Z = - ¥ .
• The function setmatrix() sets the matrix used by OpenGL to encompass all modeling and viewing transformations.
• Note that you should not use scaling when implementing the lookat() function, and the resulting matrix should not change the scale.
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• The header files supplied above should not be modified--any code you write should be contained in transform.c
• From now on your code must compile and run with either cc or CC. (You are welcome to use gcc and g++ while coding/testing, but when you submit it must use cc or CC, and still compile.)

Grading: NOT the usual 10-point scale. Only correctness will be graded; speed will not be taken into account. Any completely correct assignment will thus get 10 points.

• Turning in the assignment: Before class starts on the due date, you should do the usual: create a README (be sure to spell it that way: one word, all caps), edit the "SUBMIT =" line in the Makefile, and type "make submit". Though you may wish to create a demo to help visually debug your code, you should not turn in any demo files.