# ScaleTrotter: Illustrative Visual Travels Across Negative Scales

## TL;DR

ScaleTrotter introduces an innovative interactive visualization framework that enables seamless navigation across biological scales, from cellular nuclei to DNA atoms, addressing unique challenges posed by genome data's intertwined and detailed multi-scale structure.

## Contribution

It presents a novel multi-scale visualization concept tailored for genome data, including a scale-dependent camera model and integrated 2D/3D visuals, advancing biological data exploration.

## Key findings

- Successfully visualizes genome data across multiple scales
- Addresses unique challenges of genome data visualization
- Provides a new approach for multi-scale biological data exploration

## Abstract

We present ScaleTrotter, a conceptual framework for an interactive, multi-scale visualization of biological mesoscale data and, specifically, genome data. ScaleTrotter allows viewers to smoothly transition from the nucleus of a cell to the atomistic composition of the DNA, while bridging several orders of magnitude in scale. The challenges in creating an interactive visualization of genome data are fundamentally different in several ways from those in other domains like astronomy that require a multi-scale representation as well. First, genome data has intertwined scale levels---the DNA is an extremely long, connected molecule that manifests itself at all scale levels. Second, elements of the DNA do not disappear as one zooms out---instead the scale levels at which they are observed group these elements differently. Third, we have detailed information and thus geometry for the entire dataset and for all scale levels, posing a challenge for interactive visual exploration. Finally, the conceptual scale levels for genome data are close in scale space, requiring us to find ways to visually embed a smaller scale into a coarser one. We address these challenges by creating a new multi-scale visualization concept. We use a scale-dependent camera model that controls the visual embedding of the scales into their respective parents, the rendering of a subset of the scale hierarchy, and the location, size, and scope of the view. In traversing the scales, ScaleTrotter is roaming between 2D and 3D visual representations that are depicted in integrated visuals. We discuss, specifically, how this form of multi-scale visualization follows from the specific characteristics of the genome data and describe its implementation. Finally, we discuss the implications of our work to the general illustrative depiction of multi-scale data.