Complex Diagrams

Should you be required to work in Visio, you may well find yourself, as I did, wishing to measure your drawing in pixels. I couldn’t figure out how do do it, though Visio does support such diverse measurements as Ciceros and Didots.

I finally found the definitive answer from Microsoft: For some types of drawings, you may want to change the measurement units to pixels. However, a pixel isn’t a unit of measurement. A pixel is just a dot on a screen and the size of the dot varies for different screens. To simulate pixels, set the measurement units to points.

Needless to say, this is not satisfying. It’s true a pixel is only an on-screen measure, and is clearly only useful for a few, obscure situations, such as when creating interface mockups, wireframes, or prototypes for software, the web, or any other sort of images meant to be viewed on a screen.

Luckily, Visio provides a set of features that allow a fairly simple, two step work-around. Warning: doing this on existing Visio documents may severely distort your existing drawings. I suggest working on duplicate files, not originals.

Step One Open the File > Page Setup menu and select the Page Properties tab. In the Measurement units field select Picas.

Step Two In the same dialog box, select the Drawing Scale tab. Select the Custom Scale radio button and set the ratio to 1 p = 16 p.

That’s it. Click OK and you’re all set to go.

Why it works Picas are 6 to the inch. By setting the ratio at 1:16, Visio presents a diagram at 96 picas per inch, the same as the Windows standard of 96 pixels per inch. You could set an appropriate ratio with any of the available units, but it works well with picas, and I find it useful that all units are labeled as p.

Here is a Visio file template with the units set properly.

My master’s thesis is a system for creating good diagrams. It starts with the basics of perception and cognition, and walks the reader through the process of making appropriate choices for their particular design problem.

[download page: 10MB PDF]

From the abstract:
This thesis presents a system for the generation of complex diagrams. “Complexity” is defined as a measure of distinct data types that are independently visually encoded. Diagrams representing four or more types of data are defined as complex, while diagrams representing three or fewer are simple. Successful generation of complex diagrams is dependent on appropriate design choices. Five fundamental principles are introduced to guide the choices made by the diagram designer. The two contextual fundamental principles are “different goals require different methods,” addressing the needs of the diagram designer, and “audience brings context with them,” addressing the needs and context of the diagram reader. The three perceptual fundamental principles are the “principle of information availability,” which guides the selection and density of the diagram elements, the “principle of semantic distance,” which guides the spatial placement and grouping of the diagram elements, and the “principle of informative changes,” which guides the visual encoding of the diagram elements. A review of the diagram design process, comprising selection, encoding, and placement of the diagram components, is given. For each phase of the design process the influence of the appropriate fundamental principles is discussed, and the fundamental principles are extended into applied guidelines and suggestions.