Understanding 3D Mid-Air Spatial Manipulation in Immersive Environments: A Taxonomy and Visual Representation.

Mid-air spatial manipulation in 3D virtual environments poses unique challenges, mainly due to the absence of physical constraints. To address these challenges, several manipulation techniques emerged. However, there is a lack of systematic understanding of the design space for such techniques due to limitations of existing taxonomies. We propose a novel framework for characterizing mid-air manipulation techniques based on five orthogonal components: Input Style, Frame of Reference, Manipulation Directness, Degrees of Freedom and Transfer Function Mappings. This taxonomy enables a more fine-grained classification that captures distinctions often overlooked or conflated in previous models. In addition, we introduce a visual representation designed to support the description, comparison, and design of 3D spatial manipulation techniques. To demonstrate its utility, we apply the framework to a set of representative techniques from the literature, showing how the visual representation facilitates spotting distinctions between its different operating modes, even when such differences are subtle. Our aim is for this framework to serve not only for systematic description and analysis, but also as a practical resource for comparing, identifying design trade-offs, and informing the development of new manipulation techniques.