Approaches to interactive visualization of large-scale dynamic astrophysical environments

Dynamic astrophysical data require visualization methods that handle dozens of orders of magnitude in space and time. Continuous navigation across large scale ranges presents problems that challenge conventional methods of direct model representation and graphics rendering. In addition, the frequent need to accommodate multiple scales of time evolution, both across multiple spatial scales and within single spatial display scales, compounds the problem because direct time evolution methods may also prove inadequate. We discuss systematic approaches to building interactive visualization systems that address these issues. The concepts of homogeneous power coordinates, pixel-driven environment-map-to-geometry transitions, and spacetime level-of-detail model hierarchies are suggested to handle large scales in space and time. Families of techniques such as these can then support the construction of a virtual dynamic Universe that is scalable, navigable, dynamic, and extensible. Finally, we describe the design and implementation of a working system based on these principles, along with examples of methods that support the visualization of complex astrophysical phenomena such as causality and the Hubble expansion.