Graphing and Visualizing Multiple Variables

CS237 Assignment #3

### 1. Dates

 Out Thurs, 9/19 Due Tues, 9/24

### 2. Goals

1. Gain an understanding of the sources of experimental and computational data.
2. Learn about scientific data and identify relationships among variables in scientific data.
3. Learn to create a visualization icon showing variations in the relationships within variables in a dataset.
4. Learn how well visualizations created with your icon might translate into a 3D Cave setting.

• World of Science Encyclopedia, Volume 14, pp.119-128       Motion Of Fluids [2]
• Sensitive Chaos pp. 37-64  by Theodor Scwhenk,
• Patterns in Nature pp.53-71 by Peter Stevens
• Information Visualization: Perception for Design by Colin Ware

--Experimental Semiotics Based on Perception pp. 10-22

--Types of Data pp. 28-31

### 3. Assignment

The 2D flow handout we discussed in class contains 2D flow data around a cylinder -- you can think of it as a river flowing around a bridge pier with a circular cross section.  The data is calculated with using computational fluid dynamics (CFD) simulations, much the same way the artery or bat flow cases are.  Because this data is 2D, it is a simplified version of the data that we use in the Cave artery visualization.  The lessons we learn in this exercise will apply directly to visualizing flow quantities on artery walls or bat wings.  Because this is where the flow interacts with the bat or artery, the data is some of the most important, scientifically. It is easier to work with 2D data like this than the full 3D dataset because we have essentially a 2D visualization problem.   The  handout shows a number of different quantities all over the same space.  If they were on acetate, you could overlay all of them to see how the different values relate.

Part 1: Key/Legend Design

As we did in class for two of the images in the handout, create keys or legends for all of the data values.  For each one, it should be clear what values correspond to what visual representation.  Label the axes of the keys with numeric data values.  You’ll need to make up the numbers.  In general, zero will be clear.  Make your own choice about non-zero values and try to also fill in the units (e.g. meters/second for velocity).

## Part 2: Icon Design Showing Multiple Variables

Use your understanding of the data in the 2D flow handout (from Siggraph course) to design a visualization icon for the six listed variables of the flow that clearly shows the values evident in the data. Each visual variable (length, shape, color, pattern etc.) should correspond to one data variable, the visual variation tied closely and legibly to the variation you see in a given aspect of the data (e.g. longer icon means faster flow, redder icon means greater pressure).

Try to pack as many visual variables representing aspects of the flow as you can into a single icon. You can also use how icons relate to one another to encode data values.  The various visual variables must be simultaneously legible and not confuse the reading of any other variable in the icon. When you can’t fit any more, start a 2nd icon, with a different set of characteristics from the first, to show the remaining variables. You should execute a sufficient number of permutations of each icon to encompass the range of fluctuation of the variables in the data.  When designing your icon, place a priority on immediate legibility and clarity of the relationship between the variables.

Once you have determined a suitable icon, create a visualization of the artery data by populating a 2D picture with several variations of your icon(s) that represent, as closely as you can, the fluctuations that you see in the artery data as shown in your data handouts.  Essentially, you are designing a new icon-based visualization of the same data that you have in your handouts.  Your visualization should do a better job than the handouts at illustrating the relationship between velocity, pressure etc.  Any material may be used (traditional materials, 2D computer graphics materials, etc.) to create the 2D image, as long as it can eventually make its way into digital form, via scanning, etc., so that we can look at it in the Cave.

Make a legend for us that shows how a change in each variable affects the size, shape, color, etc. of your icon(s).

Save this at the Cave and import it into your textured rectangle application.

Create 4 rectangles with that image on them.

Resize them so that you have 1 rectangle of each of the following sizes: 6 in, 1 ft, 4 ft, 8 ft.

Arrange these around the Cave and save to a file for viewing during class.

### 4. Resources

Create a new directory for assignment 3 under your courses/cs237 directory:

-         cd courses/cs237

-         mkdir asgn3

-         cd asgn3

Copy your glueconfig-asgn2 to this directory and rename it glueconfig-asgn3

-         mv ../asgn2/glueconfig-asgn2 glueconfig-asgn3

Modify the glueconfig-asgn3 file to include your images – remember to make them square (512 x 512 pixels) and .rgb or .tga format.

-         fish1 ~/course/cs237/asgn3 -> xemacs glueconfig-asgn3

Run CavePainting with glueconfig-asgn3

-         clio ~/course/cs237/asgn3 -> cavepainting cave glueconfig-asgn3

Resize and reposition the images, then save the painting – all using directions from the Assignment 2 handout and from “less \$G/shared/man/cavepainting.txt”

### 5. Questions

1. How well are data values discernable in your iconic visualization?
2. How well are relationships among data values visualized easily by your icon design?
3. What are the factors behind your choice of visual characteristics of the icon(s)?
4. How did your 2D design work as you expected within the Cave?  What was unexpected?
5. What are additional factors that need to be considered when designing visualization for the arterial walls that are different when you think about this problem in 3D in the Cave as opposed to in 2D on paper?

### 6. Checklist

o     Created and labeled six legends for the data values in the handout

o     Created a second legend for each of the data variables showing how your icon change correlates with the data value change.  Use the same range of values for the legend as you used for the handout legend.

o     Created a 2D image in digital form or scanned into digital form that has been populated with your icons and represents as closely as possible the data from the data handouts you were given.

o     Created a courses/cs237/asgn3 directory, copied and modified glueconfig-asgn3 file in that directory to load your own images

o     Resized and positioned images in space

o     Saved the painting to a file

o     Answered assignment questions and e-mailed checking and questions to dfk@cs.brown.edu

### 7. Timing Estimates

0:20 six initial legends

1:30 2D icon design, legends, and realization

1:00 import into cave and save