Investigating Tangible User Interaction in MixedReality Robotic Games Among the emerging trends in HumanRobot Interaction, some of the most frequently used paradigms of interaction involve the use of Tangible User Interfaces. This is especially true also in the field of robotic gaming and, more specifically, in application domains in which commercial offtheshelf robots and projected Mixed Reality (MR) technology are combined together. The popularity of such interfaces, also in other domains of HumanMachine Interaction, has led to an abundance in the number of gestures that can be used to perform tangible action using these interfaces. However, there are not sufficient pieces of evidence on how these different modalities can impact the user experience, in particular when interacting with a robot in a phygital play environment. By moving from this consideration, this paper reports on the efforts that are ongoing with the aim to investigate the impact of diverse gesture sets (which can be performed with the same physical prop) on the perception of interaction with the robotic system. It also presents preliminary insights obtained, which could be exploited to orient further research about the use of such interfaces for interaction in MRbased robotic gaming and related scenarios.

Toward an Efficient Hybrid Interaction Paradigm for Object Manipulation in Optical SeeThrough Mixed Reality Humancomputer interaction (HCI) plays an important role in the nearfield mixed reality, in which the handbased interaction is one of the most widelyused interaction modes, especially in the applications based on optical seethrough headmounted displays (OSTHMDs). In this paper, such interaction modes as gesturebased interaction (GBI) and physicsbased interaction (PBI) are developed to construct a mixed reality system to evaluate the advantages and disadvantages of different interaction modes. The ultimate goal is to find an efficient hybrid paradigm for mixed reality applications based on OSTHMDs to deal with the situations that a single interaction mode cannot handle. The results of the experiment, which compares GBI and PBI, show that PBI leads to a better performance of users regarding their work efficiency in the proposed two tasks. Some statistical tests, including Ttest and oneway ANOVA, have also been adopted to prove that the difference regarding the efficiency between different interaction modes is significant. Experiments for combining both interaction modes are put forward in order to seek a good experience for manipulation, which proves that the partiallyoverlapping style would help to improve work efficiency for manipulation tasks. The experimental results of the proposed two handbased interaction modes and their hybrid forms can provide some practical suggestions for the development of mixed reality systems based on OSTHMDs.