Homework 00

Fall 2000
Tuesday/Thursday 9:30am
103 Love Building
Dr. David C. Banks

Computer Graphics
Homework 00
6 hours

Copyright © 2000 David C. Banks

0.25 hours
Create a Web page for this course. Include your name and your email address.
If you've never created a Web page before, search the Web for "html tutorial".
0.50 hours
Create three .ppm images. Find and install pbmplus if you have a machine at home. Find and install xv if you your machine runs linux. Create an image (at least 16x11) called "initials.ppm", editing the text file by hand, with your initials in it. Create a 200x100 image "yellow.ppm" that is pale yellow. Create a 200x150 image "brown.ppm" that is reddish brown. You can display these images using xv. Or you can download the ppm plugin for Netscape.
If you don't know about the ppm image format, search the web for "ppm image format" to find details.
If you don't know about xv, search the web for "xv".
0.50 hours
Use ppmtogif (on xi.cs.fsu.edu) to convert your images to .gif format.

Then include them in your Web page.
If you don't know about using ppmtogif, search the Web for the manual "man ppmtogif" to find details.
3.00 hours
Write a program "grating" to create an array xDim*yDim of pixels and write it out in .ppm format. A pixel has the following member variables:
```
double x;
double y;
double z;
double weight;
double red;
double green;
double blue;
```
Your program will fill the array according to the evaluate() method. Use/modify the code below. Note that you will need to define the variable "radius".
```
void
Pixel::
evaluate(double _x, double _y)
{
double gratingValue = sin(2.0*M_PI*sqrt(_x*_x + _y*_y)/radius);
gratingValue = 0.5*(gratingValue + 1.0);

x      = _x;             // member variables
y      = _y;
z      = 0.0;
red    = gratingValue;
green  = 0.8;
blue   = 0.8;
weight = 1.0;
}
```
To fill the array, loop over the pixels and set their values using the evaluate() method. Use/modify the code below. Note that xDim tells how many pixels are in a horizontal row, whereas xMin and xMax determine their locations.
```
int   index;
for (int yi = 0; yi < yDim; yi++)
  {
  double y = yMin + (yMax - yMin)*yi/(yDim-1);
  for (int xi = 0; xi < xDim; xi++)
    {
    double x = xMin + (xMax - xMin)*xi/(xDim-1);
    index    = yi*xDim + xi;
    pixel[index].evaluate(x, y);
    }
  }
```
When writing out the file, traverse the y-direction in reverse order and scale the colors by 255.
Parse the command line so that your program can be run by saying
```
grating xDim 300 yDim 250 xMin -1.0 xMax 1.0 yMin -1.0 yMax 1.0 radius 0.5 > grating.ppm
```
If you do not know about parsing program arguments, search the Web for "parsing program arguments".
0.50 hours
Create a UNIX Makefile, so you can compile your program on xi.cs.fsu.edu by saying
```
make grating
```
If you do not know about creating a Makefile, search the Web for "makefile tutorial".

0.25 hours
Use or modify this shell script "grating.csh" to call your program repeatedly, creating many .gif images.

#!/bin/csh

# Parse the command line
set num = $#argv
if ($num != 1) then
  echo usage: $0 numImages
  exit
endif

if ( ($1 > 0) && ($1 < 1000) ) then
  echo Making $1 images
else
  echo Argument out of range.
  exit
endif


# Make a bunch of .gif images
set flags = "xDim 200 yDim 200 xMin -2.0 xMax 2.0 yMin -2.0 yMax 2.0"

set count = 0
while ($count < $1)
  set radius = `echo "0.9^$count" | bc -l`
  echo $radius

  if ($count <  10) then
    set count = 0$count
  endif

  if ($count < 100) then
    set count = 0$count
  endif

  echo grating $flags radius $radius '|' ppmtogif > grating.$count.gif
  grating $flags radius $radius | ppmtogif grating.$count.gif
  @ count += 1
end

If you do not know about csh scripting, search the Web for "csh scripting".

0.50 hours
Edit your Makefile so that typing
```
make grating.gif
```
will cause (1) the program to be compiled (if necessary), (2) the script to execute and create 80 images, and (3) gifmerge to convert them into the animation "grating.gif".
Type "make grating.gif" to create an animated gif. Insert it into your Web page. Make it loop at least twice.
If you do not know how to use gifmerge, search the Web for "gifmerge".
0.25 hours
From the code's parent directory, create a tar file grating.tar and gzip it. Put a link to the .tar.gz file from your Web page.
If you do not know about using tar, search the Web for "tar tutorial".
0.25 hours
Print out your Web page. Put it on the cover of your notebook.

Print another copy of your Web page.
Print 2 copies of the homework 00 grade sheet.
Print this page.
Print the pbmplus home page.

Print your .ppm files (as text). The first few lines will be enough.
Print your code and headers.
Print your shell script.
Print your Makefile.
Put them inside your notebook to turn in.
Extra credit (100 points)
Write a program to draw a bunch of spheres with different colors, different radii, different centers. Convert the ppm file to gif. Put it on your Web page, print it for your notebook, include the source code.
Extra credit (100 points)
Make your program read the center, radius, color for each sphere from the command line. Drive it with a script so that the spheres move. Make a gif animation. Put it on your Web page.