We have developed a paradigm for interacting with visualizations based on the notion of physicalization. This uses the metaphor of creating "physical" objects to represent abstract data objects. This paradigm was used in the creation of SDM, a set of interactive techniques for 2D and 3D visualizations.

In the term SDM (Selective Dynamic Manipulation), "selective" reflects our goal for providing a high degree of user control in selecting an object set, the properties they affect, and the degree to which a user action affects the visualization. "Dynamic" refers to the interactions that occur in real-time. It also speaks to a belief that interactive animation provides better contextual information in an action or operation. "Manipulation" indicates the types of interactions we provide, where users can directly move objects and transform their appearance to perform different tasks.

Current static visualizations are limited in several important ways:

• Users are not able to focus on different object sets in detail while still keeping them in context with the environment.
• When the information space is dense, there will be a lot of clutter and object occlusion.
• A data set may contain elements that have vastly different values. Thus, some objects may be dwarfed when shown in the scale used for the entire data set.
• Many visualizations only allow users to view the underlying data, and do not provide tools for classifying sets of objects and saving those classifications.
• It is difficult to compare quantities represented by graphical objects which are not spatially contiguous.

The SDM paradigm deals with these difficulties by providing object-centered selection, direct object manipulation through the use of handles, and a "physics" of objects that supports malleability and flexible control. Every object in a graphic set correllates with a unique object in the data set. Each object in a graphic set uses the same visual specifications.

For example, a data set of supply centers might be visualized as a set of cylinders; where the materials-weight attribute is mapped to the height of the cylinder, and the longitude and latitude attributes are mapped to the x and y location of the cylinder.

These components are illustrated in this sequence of SDM sample visualizations which illustrate the power of this approach.