The use of head-mounted display technologies for virtual reality experiences is inherently single-user-centred, allowing for the visual immersion of its user in the computer-generated environment. This isolates them from their physical surroundings, effectively preventing external visual information cues, such as the pointing and referral to an artifact by another user. However, such input is important and desired in collaborative scenarios when exploring and analyzing data in virtual environments together with a peer. In this article, we investigate different designs for making spatio-temporal references, i.e., visually highlighting virtual data artifacts, within the context of Collaborative Immersive Analytics. The ability to make references to data is foundational for collaboration, affecting aspects such as awareness, attention, and common ground. Based on three design options, we implemented a variety of approaches to make spatial and temporal references in an immersive virtual reality environment that featured abstract visualization of spatio-temporal data as 3D Radar Charts. We conducted a user study (n=12) to empirically evaluate aspects such as aesthetic appeal, legibility, and general user preference. The results indicate a unified favour for the presented location approach as a spatial reference while revealing trends towards a preference of mixed temporal reference approaches dependent on the task configuration: pointer for elementary, and outline for synoptic references. Based on immersive data visualization complexity as well as task reference configuration, we argue that it can be beneficial to explore multiple reference approaches as collaborative information cues, as opposed to following a rather uniform user interface design.

翻译：头戴式显示设备用于虚拟现实体验时本质上是单用户中心的，允许用户视觉沉浸于计算机生成的环境中。这使用户与其物理环境隔离，有效阻止了外部视觉信息线索（例如用户之间的指向和引用某个物体）。然而，在与同伴共同探索和分析虚拟环境中的数据时，此类输入在协作场景中具有重要性和必要性。本文研究了在协作式沉浸式分析（Collaborative Immersive Analytics）背景下，设计不同方法以进行时空参照（即视觉突出虚拟数据对象）的能力。对数据进行参照是协作的基础，影响着感知、注意力及共同理解等方面。基于三种设计方案，我们实现了多种在沉浸式虚拟现实环境中进行空间和时间参照的方法，该环境以3D雷达图（3D Radar Charts）形式呈现时空数据的抽象可视化。我们开展了一项用户研究（n=12），以实证评估美学吸引力、可读性及总体用户偏好等维度。结果表明，用户一致倾向于采用所提出的定位方法作为空间参照，同时揭示了因任务配置不同而对混合时间参照方法的偏好趋势：针对基本任务偏好指针式，针对概要任务偏好轮廓式。基于沉浸式数据可视化的复杂度及任务参照配置，我们认为探索多种参照方法（而非采用统一界面设计）作为协作信息线索可能更有益。