Gradients and 2D Visualization of Multiple Variables

CS137 Assignment #2

1. Dates

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 with streamlines and texture fields showing variations in the relationships within variables in a dataset.

4.      Explore and experiment with color and shape gradients, layering, metaphorical reading of visual elements, and legend design.

3. Readings

·         World of Science Encyclopedia, Volume 14, pp.119-128. Motion Of Fluids [2]

·         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

·        Comparing 2D vector field visualization methods: A user study, by David H. Laidlaw, Michael Kirby, Cullen Jackson, J. Scott Davidson,
        Timothy Miller, Marco DaSilva, William Warren, and Michael Tarr. TVCG, 11(1):59-70, January 2005.

·       Strategies for the Visualization of Multiple 2D Vector Fields, by Timothy Urness, Victoria Interrante, et al. IEEE CG&A, 26(4):74-82, July 2006.

4. Assignment

4.1 Part A: Gradient Design

    A gradient is defined for this assignment as any gradually changing visual element or visual quality: a color blend or fade, a morphing texture, a thickening line or accumulation of lines, a gradual change in orientation of a line, form, or pattern. After reading about the variables involved in fluid flow, begin the design process for a 2D visualization of fluid flow by generating a resource library of as many different kinds of gradients as you can imagine. A list of some possible qualities or characteristics follows. Consider the legibility of each gradient; its change should be easily perceivable. Consider also its legibility in a complex “layered” situation, in the company of other gradients. Not only should the gradient be legible in “mixed company”, but also it should not interfere with the legibility of its neighbors. You can highlight the “combinability” of your gradients by showing them in tandem usage with others. Finally, consider the “intuitive reading” of your various gradients: the possible interpretation a viewer might have of the coded meaning shown by the change that takes place in the gradient: intensification of force; increase/decrease of velocity; temperature etc.

    Make a chart with at least 15 different visual gradients, showing the nature of their change, their combinability with each other, and a set of possible applications for each one based on their intuitive readings. Your chart should culminate in five gradient compositions, each with five layered gradients, adjusted for legibility, as described above.

       Gradient types:

               Color change: Value—light to dark
                               Hue--compliment blend, temperature change,
                               Saturation—neutral to intense
                               Transparency/Opacity
               Linear shape : Thickness, length, orientation. curve/straight, zig zag or wave form: tighter or looser interval,
               Shape: Size, round/angular, simple/complex, geometric/amoebic, orientation, flat/volumetric
               Pattern: density, size of unit, direction/orientation
               Texture: contrast, opacity, rough/smooth

4.2 Part B: 2D Graphing of Multiple Variables

    Design a 2D visualization for fluid flow around a cylinder, with six variables, based on the image in the handout. Begin by assessing the data, and consulting your gradient library for possible visual representation for each variable in the data. Ideally, the gradient you choose for a specific variable should have an intuitive reading connected with your understanding of the variable: e.g. velocity should look like velocity. In addition, your choices should take layering into account: the gradients should not interfere with each other in combination. Visual simplicity of the whole will enhance individual value legibility and legibility of data interconnection.

    Do three of these compositions, experimenting with different combinations of gradients.

    Design a clear, well-organized legend or key for each of your visualizations, detailing each gradient’s change in relation to the changing value of each data variable. 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).

4.3 Other tasks

As part of each assignment, there will be a few questions that you should answer.  These can be found at the end of this handout and your answers should be emailed to the TA (daf@cs.brown.edu) by 9 AM (an hour before class starts) on Wednesday 10/11.  Most of these are very short questions intended to help guide you through the assignment.  They should not take long to answer.  Most of the time, a very brief, one sentence or less, answer is sufficient.

5. Questions (answer briefly)

1. How well are data values discernable in your visualization?
2. How well are relationships among data values visualized easily by your design?
3. What are the factors behind your choice of visual characteristics that show gradient?
4. What are additional factors that need to be considered when designing visualization for the bat wings that are different when you think about this problem in 3D in the Cave as opposed to in 2D on paper?