CS 559 - Computer Graphics

Content-Type: text/html; charset=ISO-8859-1 CS 559 - Computer Graphics - COURSE NEWS

CS559
Fall 2003

news
basics
calendar
assignments

project 1

C++hints
FlTk
LibTarga
zoomer

Reader

Are you looking for the basic course information page?

Fri, 26 Sep 2003

Sample Red Eye Pictures

There are some sample targa images with red eyes for you to reduce in p:/course/cs559-gleicher/public/SampleData/RedEyes.

Programming and Project Grading

A student asked...
> When you grade project 1 are you going to take into account how
> compact the code is, or how fast it takes, or how well we know c++?
> asssume the code is well documentated. I was just wondering...

good question...

short answer: no
long answer: indirectly.

what's more important (especially on this project) is that your program works correctly
if you write bad code, you will have a hard time getting it to work reliably and test it. you will spend more time getting bad code to work than it would take to write good code.
efficiency doesn't matter within reason. if it takes a few seconds to process a small image, that's ok. if it takes several minutes to process a small image, then you have a problem. of course, if your program is that slow, you won't be able to test it thoroughly, and you'll spend a lot of time waiting for it.
on using C++ - clearly, you need to use C++ well enough to make sure your program compiles and runs. we will not care if you use fancy c++ features (in fact, i don't recommend it). we won't even check to see if your program leaks memory or stuff like that. again, its to your best interest to not have silly programming problems since its harder to make the program work with these issues.
when we "read" your code, our checklist will have things like "can we identify where in the code you do X and what algorithm you used for it."
occassional crashes are a form of not really working

Thu, 25 Sep 2003

A clarification on Written Assignment 2

My sloppy terminology is confusing some people.

First, I use the term "ideal" or "true" low pass filter to mean a filter whose attenuation is zero outside of its passband and one inside of its passband.

Second, saying "squaring" the filter kernel in 2B and 2C is not well defined. By squaring, I mean applying the filter to the signal twice, or applying the filter to itself (and then to the signal). This means convolving the kernel with itself in the time domain, or multiplying it by itself in the frequency domain.

Third, in my notes in the reader, there are some minor arithmetic mistakes in the pictures that have the convolution examples. I also play a little fast and lose with some of the notation of convolution. Specifically, the signals get flipped around, and I don't really say where the results "start." For the purposes of the assignment, it doesn't matter much - if you reverse the order of the convolution kernels, you'll get a different answer thats OK, and we aren't too specific about where the short signals begin and end.

To clarify some of the questions about convolution, I fixed some of my signal processing notes. Pages 14-16 have been redone. Hopefully these will help.

Wed, 24 Sep 2003

Converting Color to Gray Values

Because our eyes are more sensitive to green, an equally bright green, blue, and red will not appear equally bright. This means that if you are converting between color and grayscale, the color red (255,0,0) should not turn into the same brightness as the color green (0,255,0).

The exact ratios vary. One simple one is to say that green is twice as sensitive as red is twice as sensitive as blue, which gives the rations for R,G,B as 2/7, 4/7, 1/7, or .28, .57, .14. I have also seen systems that use r = 0.212671, g = 0.715160, b = 0.072169.

The closest thing to an "official" standard is what is used in NTSC (the North American video standard) to compute brightness from colors. That's: Y = 0.30R + 0.59G + 0.11B.

Written Assignment 2 Updated (again)

There were some changes made to written assignment 2.

There is one question that was poorly worded, and another question that you should just skip.

(this actually only got put on the web Wednesday morning at 11:15am - sorry!)

Mon, 22 Sep 2003

Project 1 Announcement

Project 1 has been added to the website. Look at the navigation bar to the left!

Extra Sessions Above and Beyond Class

As I mentioned the first week, in the past we've had "extra meetings" of 559 to discuss material that is beyond what we can talk about in class.

We'll have one of these on Monday, September 29th at 4pm. Tentatively scheduled for 1325 CS. The topic will be painterly rendering. The required reading will be a paper or two on the subject. For this meeting, a graphics graduate student will lead the discussion.

This week, the topic of discussion will be painterly rendering (to help you do something cool for Project 1). There are two papers to read in /afs/cs.wisc.edu/p/course/cs559-gleicher/public/ExtraReader

Bug in ZoomerWindow

There's a nasty bug in ZoomerWindow that will cause your program to crash after you do a save. Finding it is actually good practice in trying to understand why its important to make some software engineering decisions correctly, especially dealing with shared data.

The problem is that the "writeTarga" method of TargaWindow uses reverseRows, which is destructive (it moves the image data to a new place). This would be OK, since the TargaWindow is updated appropriately. However, since the Zoomer Window keeps a pointer to the data, this pointer will be dangling after the TargaWindow gets updated.

I have fixed the bug (albeit in a non-elegant way), and put a warning into the header file.

Sun, 21 Sep 2003

dirent.h error

There are various fixes for this. The easiest is to change the standard include directories to be $(FLTKHOME);$(FLTKHOME)/FL;

filename.h does a #include "dirent.h" and it can't find that in the include directory list.

Thu, 18 Sep 2003

Written Homework 2 has been Updated

We just looked over the second written assignment and decided to make question 1 easier. If you've already printed it out, you should do so again. Sorry for the inconvenience!

If you can't find a copy of the OpenGL "Red Book"...

Any older version would be OK. Borrowing it from a friend (anyone who has taken this class in previous years) might work too.

The complete text of the book is online at http://fly.cc.fer.hr/~unreal/theredbook/, but I don't know how convenient this is.

Project 1 Preliminary Announcement

You might have noticed that project one is due in less than 3 weeks.

In the event that you want to get started early, we have posted the basic outline of the project here.

This should be enough so that you can get started on it. More details are forthcoming.

Wed, 17 Sep 2003

Written Homework 2 Posted

The second written homework assignment (imaging math) has been posted. This assignment is good practice for doing the project.

Update to ZoomerWindow

Someone found a bug (thanks!) - it's been fixed.

Tue, 16 Sep 2003

Some notes on the reader...

The link to the web page about the reader was broken. It's fixed now

I tend to describe things by the author, so "Foley and van Dam" is the Chapter in the Reader entitled "Achromatic and Chromatic" light.

On thursday, we'll talk about sampling some more, talk about quantization, dithering, and error diffusion, and hopefully get to color systems.

Zoomer Demo

I just put up a new demo FlTk/LibTarga program. (there's links from the web page). It's a slightly more interesting demo. Understanding it may help you make a better Project 1 (which is coming soon)

Mon, 15 Sep 2003

No Office Hour for Mike on 9/16

I will not have my office hour on September 16th. Trust me, what I will be doing is even less fun than office hours.

LibTarga Web Wierdness

You make have noticed some wierdness with LibTarga on the CS559 website. I think it all has been corrected.

Sat, 13 Sep 2003

JPEG support in FlTk

It seems that the version of FlTk built for the CSL machines does not have JPEG support. You won't need it. But if you think you want it, beware, since its not there

If you want to read/write images, you should look at libtarga. Actually, you will want to read images soon (libtarga is part of next weeks programming assignment.)

(hint - if you can't find libtarga, look to the left of this window)

Fri, 12 Sep 2003

FlTk Problem

Some of you may have had a problem linking your program with fltk. The symptom will be a cryptic error message involved a "public static" such as:
LNK2001: unresolved external symbol "public: static int Fl::e_keysym" (?e_keysym@Fl@@2HA)

The problem is that we forgot to tell you in the tutorial to define the symbol FL_DLL. I will update the tutorial now, but the fix is to add the symbol FL_DLL to your "Preprocessor Definitions" on the C++/Preprocessor tab of the Property pages of your project.

Thu, 11 Sep 2003

FlTK path problem

The original version of the tutorial did not tell you to add FlTk to your PATH environment variable. This is important in order to get your program to run. The tutorial has been updated.

Wed, 10 Sep 2003

Visual Studio Problem

As we mentioned in Monday's announcement, the CSL is having problems getting the Visual Studio compiler to work. We do not know when the problem will be corrected.

The problem seems to arrise from an attempt to put debugging information onto AFS.

The workaround for this problem is to do all of the work from the local disk of the machine (e.g. put your files into C:/TEMP or on the desktop).

Working on the local disk is preferable because it is much faster than accessing files over the network. However, do not forget to copy your files back to your home directory - Files you leave on the machine will be cleaned out when you log off.

Tue, 09 Sep 2003

Homework 1 Solution

The solution to homework 1 is posted.

Mon, 08 Sep 2003

An interesting page about color vision

Shirley's book isn't that great on color. For a more interesting discussion to augment what I'll say in class, check out this page.

Another good reference is from Adobe.

FLTK Tutorial

There will be a session to go over the FLTK tutorial in B240 on Thursday, 9/11, at 4:00, after class.

The CSL will not have the computers in B240 properly configured to use FLTK until Wednesday or Thursday this week. This assignment is not due until Tuesday, 9/16. Liz (the TA) will also be down in B240 on Monday 9/15 11:00-12:00.

A Note on Homework #1:

Someone has pointed out that on question 4, in the degenerate case (when the vectors are co-linear, or one or more of them is zero), this problem is much more difficult.

You may assume that the two vectors in question 4 are not co-linear, and that they both have non-zero magnitude.

Wed, 03 Sep 2003

Additional Readings on Human Vision

I am putting papers that you might be interested in in the afs directory /p/course/cs559-gleicher/public/Readings.

Today, I put two additional papers about human vision (one is specifically about the psychology of watching movies). These are what I'm reading to prepare for lectures. Of course, these readings are optional, but in case you are interested I'll make them available

Some of the course reader papers will be available in this directory as well. Please do not print the files - it is actually more economical for you to buy the reader from DOIT (somebody actually pays for the printing we do on the department printers). I am putting the files there only if you are interested in saving a tree or two.