CS 447/647: Image Synthesis

Assignment 0: Hello, World

Due: January 23

Description

This assignment will get you acquainted with lrt.

Step 1

lrt has been developed and tested on Linux.  If you're using something else, you're on your own.  You will need libtiff installed.

• Download lrt.tar.gz from here.
• Type gunzip lrt.tar.gz in the directory with lrt.tar.gz. The result is a file named lrt.tar.
• Type tar xvf lrt.tar. This will extract the files you need into a new directory called lrt.
• Compile lrt using gmake.

Step 2

Once you have successfully compiled lrt, you can try rendering some images.

• Download the file decls.rib to your working directory.
• Download the file hello.rib to your working directory.
• Type lrt decls.rib hello.rib to begin rendering.

You will see some messages from lrt, and it will begin printing a sequence of 'p's followed by a sequence of '+'s to the screen to let you know it is working. After a minute or so (it will print about 50 '+'s), the rendering will finish. You will have a new image, hello.tiff, in your directory. View this with your favorite image viewer. Congratulations! You've rendered your first image with lrt.

Open hello.rib in a text editor. The first few lines are comments, followed by commands that specify the desired image resolution and format. Try reducing the resolution to half the current size, and reducing the pixel samples from 2x2 to 1x1, and render the scene again. It will be smaller and have some jaggies, but it will render much quicker. This will be useful later in the course; you'll want to do lots of quick and dirty renders for debugging.

Next in the hello.rib file are commands to set up the camera and specify a view transformation matrix. Finally, after the WorldBegin line, you will find the description of the scene. You should be able to figure out the meaning of the lines that describe the two light sources. The polygon meshes that fill the rest of the file are not terribly human-reader-oriented, but you can probably spot the lines that specify surface shaders and colors for materials. Experiment with changing the colors of materials and lights, and with changing the position of the light sources.

You will find several other scene files here. Feel free to experiment; don't forget to always use the decls.rib file when you render. You can find detailed information about the RIB file format through the links on the main class page.

Step 3 (the big one)

You can find the lrt book here. You should read through the first three chapters of the lrt book.

As a quick check on what you've read, answer the following questions about lrt. One line (and sometimes one word) answers for each will suffice.

1. What physical quantity do we measure along a ray?
2. What lrt class is used to describe the reflection of light at a point?
3. How are vectors and normals treated differently?
4. What's the difference between Intersect and IntersectP?
5. What lrt class is used to describe the intersection between a ray and a shape?  Give a brief description of each field in this class.
6. What kind of coordinates are used to parameterize a triangle?

Submission

Write up the answers to the questions in part 3 as a web page, and mail the URL to the TA. 

When submitting assignments, NEVER mail the TA anything other than a URL. 

Each assignment will require you to create a small web page.  Typically this page will contain answers to any written questions, links to source code, and images.

Grading

This homework does not count directly to your course grade except in the sense that you will not pass the course if you don't complete it.  We're not kidding about this -- you need to get familiar with lrt in order to be successful in the later assignments.