CS 4451 Computer Graphics

Assignment #1

Due: Friday, February 8, 2002, 12:00 Midnight

Purpose: To demonstrate understanding of 3D viewing.

Discussion: This assignment is Foley, van Dam, Feiner, Hughes (FVFH) Exercises 6.1 and 6.2 for perspective projections (N_per), with clipping in 3D (not in homogeneous coordinates), implementing FVFH Figure 6.46. You are to write a program that displays a (clipped) wireframe model of the house in FVFH Figure 6.24 from any number of different views. Your program will essentially be transforming, clipping and drawing 3D lines.

Implementation Requirements:

(Some of these requirements are for ease of grading)

1. Your program must accept from stdin the parameters defining a perspective projection view volume, where a set of viewing parameters consists of six lines of text. The following input format and order must be used, and constitutes one set of view parameters (remember, the program must be able to read any number of these sets of parameters and produce the corresponding view each time):

Define the View Reference Coordinate (VRC) System (and thus the view plane):

View Reference Point (VRP) - three reals: VRP_x, VRP_y, VRP_z

View Place Normal (VPN) - three reals: VPN_x, VPN_y, VPN_z

View Up Vector (VUP) - three reals: VUP_x, VUP_y, VUP_z

Define a window on the view plane:

Viewplane Window Bounds - 4 reals: u_min, u_max, v_min, v_max

Define the semi-infinite perspective projection view volume:

Projection Reference Point (PRP) - 3 reals: PRP_u, PRP_v, PRP_n

Define a finite view volume:

Front, Back Clipping Planes (F, B) - 2 reals: F_n, B_n

An example set of parameters:

0 0 54

0 0 1

0 1 0

-1 17 -1 17

8 6 30

1 -23

Your program will be graded by redirecting to stdin from a file, e.g: %prog1<grade.data where grade.data is the name of a file containing sets of view parameters. Code accordingly!

2. The VRC system is right-handed: your 3D transformation matrices should reflect this (e.g., a translation matrix should have t_x, t_y, t_z in the rightmost column, not the bottom row.)
3. Your program will be tested with view parameters corresponding to FVFH Figures 6.29, 30, 34, and 41, and possibly others. Your program must pause between each view, waiting for a left mouse button press. Use either the OpenGL aux library libaux.a or GLUT library libglut.a to provide this mouse functionality.

Test data can be assumed to be in the correct format and order, but your program should provide an error message (but not terminate) for input that results in an invalid or an unreasonable view, such as the following:

• VPN is degenerate (zero)
• VUP is parallel to VPN
• PRP is on the view plane
• View plane window is reasonable (eg, u_max != u_min)
• B is in front of F

4. Please make the window on the display screen (viewport) 500 x 500!
5. The program must be written in C and compile and run using OpenGL on an SGI Indy workstation in the CoC SGI lab. YOU must write the code that implements 3D perspective viewing and clipping, and any matrix math functions. You MAY use gluOrtho2D(), but YOU MAY NOT use the following OpenGL calls: glFrustum(), gluPerspective(), gluLookAt(), gluProject(), glTranslate(), glRotate(), glScale(). glClipPlane().
6. You must write a function to compute all vertex/matrix functions you use (i.e. dot product, cross product, matrix multiply, etc).
7. You must write function to perform EACH of the eight transformations (T_vrp, R, T_prp, SH_par, S_per, clipping in 3D, M_per, M_VV3DV ).
8. ALL source code you submit must be well documented (documentation is an indicator of understanding!)
9. You MUST include a REAMDE file that details how well your program works, any quirks it might have, and a statement that you are trying for the extra credit (if you are doing so.) In addition, include the name of the SGI workstation that you used to compile and run the most recent version of your code.
10. See the grading sheet for more programming requirements.

Submission:

1. Ensure your name and login name appear in each file you submit.
2. Put the files you are submitting (including the Makefile you used) in a directory on a College of Computing UNIX machine. Name your directory last_first_1 where “last” is your LAST NAME and “first” is your FIRST NAME (The "_1" corresponds to the assignment number). Then, from the parent directory, execute the following command:

% tar -cvf last_first_1.tar last_first_1

For example:

I would create a directory named Parry_Mitch_1,

% tar –cvf Parry_Mitch_1.tar Parry_Mitch_1

This would tar everything in the directory Parry_Mitch_1 and put it into the file named Parry_Mitch_1.tar.

Then mail the tar file to parry@cc.gatech.edu.

3. You can submit as many times as you want, but only the submission closest to the due date/time will be examined and graded.

Hints and help:

1. FVFH Chapters 6.5.2 (implementing perspective projection) and 6.5.6 (steps in the overall viewing transformation), Figures 6.55 (clipping to the 3D canonical perspective projection view volume) and 6.59 (matrices involved in the viewing transformation).
2. IRIS InSight on-line documentation for OpenGL and the auxiliary and utility libraries; UNIX man pages for OpenGL; OpenGL programming texts; http://ask.ii.uib.no/ebt-bin/nph-dweb/dynaweb/SGI_Developer/OpenGL_PG/ for openGL and GLUT library,
3. Sample code and a makefile are available on the webpage.

Grading criteria:

FVFH Figure 6.24 wireframe house

Perspective view pipeline of FVFH Figure 6.46

Clipping in 3D (NOT homogeneous coordinates, i.e., N_per, not N’_per)

1. Submission and Compilation (and following directions) ______

-5 name and login name not on each submitted file

-5 does not accept view parameters in the order specified

-5 no README file (and the required information within)

-50 does not accept view parameters input from stdin

-100 prohibited calls used

-100 does not compile on SGI Indy

2. Documentation ______

-5 to -25 insufficiently documented (code not commented, functions not explained, etc.)

3. Code _______

-10 vector/matrix functions not used

-10 separate functions for each transform not used.

+10 T_vrp

+10 R

+10 T_prp

+10 SH_par

+10 S_per

+10 clipping in 3D

+10 M_per

+10 M_VV3DV

+10 divide by W

+10 matrices constructed and multiplied correctly, and used in the correct order

4. Run-time _____

- 40 aborts without display

-10 invalid views not checked and handled with an error message

-5 viewport not 500 x 500

-5 does not use left mouse button press for each new view

Extra Credit (+25 points, maximum):

Add the following capability:

1. (+10 pts) Parallel and perspective projections. Use FVFH Chapter 6.5.1 for implementing parallel projection viewing. Use a GLUT pop-up menu or the keyboard (‘p’ = perspective, ‘o’ = parallel) to select between types of projections.
2. (+10 pts) Clipping to the canonical parallel projection view volume using the 3D Cohen-Sutherland outcode clipping algorithm (FVFH Chapter 6.5.3).
3. (+5 pts) GLUT pop-up menu is used to select between types of projections.