The Data

2D fluid flow past a cylinder

    You can think of it as a river flowing around a bridge pier with a circular cross section. The data is calculated 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 bat visualization. The lessons we learn in this exercise will apply directly to visualizing flow quantities on bat wings. Because this is where the flow interacts with the bat, the data is some of the most important, scientifically. It is easier to work with 2D data like this rather than the full 3D dataset because we have essentially a 2D visualization problem. This handout shows a number of different quantities, all of them over the same space. If they were on acetate, you could overlay all of them to see how the different values relate.

Velocity – speed and direction. Speed is arrow size.

Turbulent charge. Gray is zero. Analogous to electric charge

Rate-of-strain tensor. How particles squish.

Vorticity – how particles spin. Gray is no spin, lighter is clockwise, darker is counterclockwise.

Turbulent current. Has a magnitude and direction. Analogous to electric current.

Amount of squishing. Eccentricity of the ellipses to the left. Gray is no squishing.

[The rest of this document is notes from an earlier class -- feel free to peruse and use any ideas that sound appealing.]

Now What?

NPR for Scientific Visualization

SIGGRAPH ’01, Monday Aug. 13

Just try something! The more you experiment the more you will learn. If you get stuck, switch to something else.

Take notes. Jot down what you want to try. Jot down any surprises.

Share what you are doing and thinking with your neighbors.

Which media are good for representing which data values? Experiment with representing one or two data images at a time. Try painting. Use palettes to mix colors and to thin the paint. Apply it with brushes, a knife, or your fingers. Scrape it off or smear it around with a paper towel or finger. Also try the markers, pastels, and crayons. Use the different paper types.

What visual representations work for scalars? Vectors? Tensors? Try washes, icons, curves, texture.

How many quantities can you represent in one visualization? Experiment with layering visual representations. Mix media.

What are some tradeoffs in showing multiple values? Consider, for different data values:

Small icons vs. large icons,

A continuous representation, like a wash, vs. a discrete representation, like icons

High contrast vs. low contrast,

Different hues or lightnesses,

What visual abstractions for the data are particularly efficient (i.e., use little space on the paper to show much information)?

Clean your brushes from time to time.

Start with lighter colors and work towards darker ones.

Try the same idea out more than once...it may look very different the second time.

Try the same idea out using a different medium...if you used marker the first time, use paint the second time.

Think about the design process you are doing here. Can you make the concept clearer? Can you identify some new things to try when you get back to the real world?