Relational information between different types of entities is often modelled by a multilayer network (MLN) - a network with subnetworks represented by layers. The layers of an MLN can be arranged in different ways in a visual representation, however, the impact of the arrangement on the readability of the network is an open question. Therefore, we studied this impact for several commonly occurring tasks related to MLN analysis. Additionally, layer arrangements with a dimensionality beyond 2D, which are common in this scenario, motivate the use of stereoscopic displays. We ran a human subject study utilising a Virtual Reality headset to evaluate 2D, 2.5D, and 3D layer arrangements. The study employs six analysis tasks that cover the spectrum of an MLN task taxonomy, from path finding and pattern identification to comparisons between and across layers. We found no clear overall winner. However, we explore the task-to-arrangement space and derive empirical-based recommendations on the effective use of 2D, 2.5D, and 3D layer arrangements for MLNs.

Augmented Reality (AR) displays have been suggested as shared-space technology to support remote collaboration, e.g., in design and building tasks. But with AR displays, the shared space typically consists of only the virtual work objects (e.g., design artifacts) while collaborators' interaction is grounded in their individual, physical environment. This can become problematic during activities that involve the positioning of virtual objects because the collaborators may require shared spatial references to coordinate their actions. In a lab experiment with 16 dyads, we studied how collaborators deal with that issue, and whether the provisioning of additive, virtual landmarks influences collaboration. As a result the landmarks improved user experience and decreased the reported temporal demand. In addition, we identified task-specific problem situations and provide implications for the design of distributed ARs to facilitate the collaborative positioning of virtual objects.