CSE 681 - Winter 2011

Homework #1
due Monday, Jan. 10
submit on or before 11:59:59pm on Monday

This is to get you started early on code you going to have to write at some point anyway. This should not be a difficult exercise. If you have problems writing this code, then you should see me about what classes you should be taking.

You are to write two programs. One simply outputs a valid .ppm file and the other will read in and parse a test file. See below for details.

These programs will be graded under UNIX. Use the submit command to electronically submit your files. You can do

man submit

If you program in C, your submit should look something like this (the files can appear in any order):

submit c681aa hw1 ppm.c parser.c makefile

submit c681aa hw1 ppm.cpp parser.cpp makefile

You have to submit a makefile that the grader can use to compile the programs. You can do a man make to learn more about the make command, but it's probably better to look online for information or just use the information from the CSE681 web pages.

Here is a sample makefile that you can use. You can modify this makefile for subsequent assignments.

make ppm
ppm

make parser
parser <input filename>

DO NOT USE YOUR OWN NAMING CONVENTIONS FOR EXECUTABLE FILE. The grader can automate some of the compiling and executing of programs if you adhere to the naming conventions in the lab and homework specifications. You will lose points if you deviate from these and subsequently slow down the grading process.

The objectives reason for this homework assignment are to:

1. make sure everyone has the requisite programming skills for the class
2. get you started on some of the more general-purpose code that needs go into your lab assignment
3. make sure you know how to submit programs (and to make sure submit is set up properly and is working)
4. make sure you can use a simple makefile

1. OUTPUT PPM FILE
   This code will be part of all the lab assignments.
   Write a small test program to make sure you understand how to write out ppm files. Portable pixmap format (ppm) is a very simple color image file format. We will be outputting images in this format in all the labs throughout the quarter.
   • PPM man page
   • sample PPM image
   You program should write out a ppm file, such as the sample PPM image above, to a file called output.ppm. Under UNIX, use convert to convert it to a .jpg format, then display to view it. So the grader should be able to do the following under UNIX:

   make ppm
   ppm
   convert output.ppm output.jpg
   display.jpg
   

2. SCENE FILE PARSER
   This code will go right into Lab 2. Also, the code that parses the transformation commands will be used in an upcoming homework assignment.

   Write a parser for an input text scene description file (see format below), reading in values and setting variables in a scene description data structure. Print out the output filename and the number of spheres.

   Data Structure

   Set up data structures for the following items. The variables in the data structures are the ones that are in the input file (see below).

   • camera
     • position
     • center of interest
     • view angle
     • aspect ratio
     • hither and yon clipping distances
     • tilt angle
     • x and y resolution
   • sphere (unit radius, centered at origin)
     • material properties
     • 4x4 transformation matrix
   • light
     • position
     • intensity
     • falloff
   • scene
     • camera
     • output filename
     • multiple spheres
     • multiple lights
     • background color
     • ambient value

   Simple Scene File Format
   

   • bracketed values are floats unless they end in:

        '_i' : integer
        '_s' : non-whitespace string
        '_ws': any text, including whitespace, terminated by the end of line
     

   • a command will always start on a new line, but can extend over multiple lines
   • commands and parameters are separated by whitespace
   • a comment line will have a '#' in the first column followed by whitespace; everything on the line until the end-of-line should be ignored.
   • for our purposes, whitespace consists of one or more spaces, tabs, linefeeds and carriage returns

   Commands
   

   # <comment_ws>
   
   sphere <r> <g> <b> <t_s> <kd> <ks> <n_i> <kr>  <gl> <kt> <f>  <tr>
   
   camera <x> <y> <z> <cx> <cy> <cz> <angle> <aspect> <hither> <yon> <tilt> <xres_i> <yres_i>
   light <x>  <y>  <z> <i>  <f>
   ambient <a>
   background <r> <g> <b>
   output <filename_s>
   
   identity
   rotate [x|y|z] <angle>
   translate <tx> <ty> <tz>
   scale <sx> <sy> <sz>
   

   Sample Scene Files
   

   1. sample 1
   2. sample 2