CS 184 | Graphics | Fall 2007

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Assignment 02 - Basic Shading

Due Date

This assignment is due at 11:59pm on Thursday, September 20th. Projects turned in late will lose points as described in the policies handout. This assignment should be done alone or in pairs. You may share ideas with other groups, but you may not share code.

This assignment is worth 53 points.

Submission Details

You may develop on Unix, OS X, or Windows. The platform you use will be the one used to grade assignments. Keep in mind that there are slight variations due to OS versions, different libraries, and other factors, so you should verify that your code runs on the instructional machines appropriate for you platform choice.

We will be using the submit software for submission of this assignment. Instructions for using the submission software are here The assignment name is "basicshading".

You should include a README file that at the minimum contains the following data:

1. Your (and your partner's) name,
2. The platform your code runs on,
3. The location of your source code (i.e. indicate who in your group has done the submission, and on what platform). Only one of the people in your group should submit the actual code. The other people should only submit the README file.

All files needed to compile your code should appear in the submitted directory. It is your responsibility to make sure that they will compile and run properly.

• Windows: The grader should be able to recompile your program by simply opening the project and rebuilding it from scratch.
• Unix and OS X: The grader should be able to recompile your program simply by typing "make".

Do not wait until the last minute to start this assignment. This assignment should be easy, but it may also be your first experience coding for graphical output. Assume the unexpected and give yourself time to deal with it.

Check the news group regularly for updates on the assignment or other clarification. We will assume that anything posted there is henceforth known to all.

You should also update your class web page to include images generated by this code. If you like, you may write code to output image directly from your software, or you can use screen shots. This class has graders so the Professor generally does not see assignments unless there was some issue in grading them that required his attention. He does, however look at the web pages. If you don't post anything there then he can only conclude that you did not do the assignment or that your results were too poor to post. It is also a nice place to show off your work to others in the class.

Overview

For this assignment, you will write a program that:

• Opens a window that contains an OpenGL rendering area.
• Displays a circular shape that will be shaded using the Phong Illumination Model for point and directional lights.
• The circular shape should occupy most of the window. If the window is resized it should update the display so that the shape still occupies most of the window and is still round.
• When space bar is pressed the program should exit.

You program will take a series of command line options:

• -ka r g b
  This is the ambient color coefficients of the sphere material. The parameters r g b are numbers between 0 and 1 inclusive.
• -kd r g b
  This is the diffuse color coefficients of the sphere material. The parameters r g b are numbers between 0 and 1 inclusive.
• -ks r g b
  This is the specular color coefficients of the sphere material. The parameters r g b are numbers between 0 and 1 inclusive.
• -sp v
  This is the power coefficient on the specular term. It is a number between 0 and max_float.
• -pl x y z r g b
  This adds a point light to the scene. The x y z values are the location of the light. The r g b values are it's color. Note that the x y z values are relative to the sphere. That is, the center of the sphere is at the origin and the radius of the sphere defines radius one. The Y direction is UP, the X direction is to the right on the screen, and the Z direction is "in your face." The r g b value are between 0 and max_float, NOT between 0 and 1 (that is, the r g b values encode the brightness of the light).
• -dl x y z r g b
  This adds a directional light to the scene. The x y z values are the direction that the light points in. The r g b values are it's color. See -pl for coordinate system notes.

There may be up to 5 point lights and 5 directional lights in a scene. The r g b values of 1.0 should be mapped to a display values of 255.

All command line arguments are optional. The default values should be a black sphere with no lights.

Optional features that you can implement for extra credit are:

• Anisotropic diffuse or specular shading
• Writing image a JPG file instead of to the screen. (Default would still be to the screen, but an optional command line argument would cause no OpenGL window to be open and file output instead.)
• Some sort of "toon" shading.
• Other shapes besides spheres.
• Multiple spheres that can shadow each other.

Other features should be clearly documented in your README file. They should be implemented through additional command line options. The behavior of the arguments specified in as required for the assignment should not be changed. Your README file should explain what your optional features are and provide example command invocations that produce nice results.

The TAs have provided some example code on the resources page to start with. You may use this code if you like or you can start from scratch. If you chose to use the TAs' code then you are responsible for figuring out how to use it. If there is a bug in that code, please bring it to the attention of the TAs immediately. Please be advised that even if there is a bug in their code do not assume that you will be allowed to turn in the assignment late.

Questions should be posted to the news group.