Uncharted Research
The Multiple Visual Attributes of Shape

Brath R., Chapter 3 in Information Visualization: Techniques, Usability and Evaluation, Cambridge Scholars Publishing. 2014

There are many different types of shape attributes that can be used to encode data for information visualizations. Prior art from many fields and experiments suggest that there are more than a half dozen different attributes of shape that can potentially be utilized to effectively represent categoric and quantitative data values.