  We examine visual representations of data that make use of combinations of
both 2D and 3D data mappings. Combining 2D and 3D representations is a common
technique that allows viewers to understand multiple facets of the data with
which they are interacting. While 3D representations focus on the spatial
character of the data or the dedicated 3D data mapping, 2D representations
often show abstract data properties and take advantage of the unique benefits
of mapping to a plane. Many systems have used unique combinations of both types
of data mappings effectively. Yet there are no systematic reviews of the
methods in linking 2D and 3D representations. We systematically survey the
relationships between 2D and 3D visual representations in major visualization
publications -- IEEE VIS, IEEE TVCG, and EuroVis -- from 2012 to 2022. We
closely examined 105 papers where 2D and 3D representations are connected
visually, interactively, or through animation. These approaches are designed
based on their visual environment, the relationships between their visual
representations, and their possible layouts. Through our analysis, we introduce
a design space as well as provide design guidelines for effectively linking 2D
and 3D visual representations.
