A wide range of tools, machines from diverse industries are operated by the precise rotation of physical devices (e.g., knobs, encoders). Literature proved that Mixed Reality can provide rotation guidance by superimposing digital cues onto the real environment. However, existing studies primarily focus on speed rather than precision and lack proven solutions with standard comparison methods. We presented a novel open MR testbed to evaluate MR rotation guidance cue designs. It comprises (i) a 3D-printed structure with a controller mount for MR cue tracking, (ii) an industrial encoder (resolution 1.8º), (iii) an Esp32 microcontroller, (iv) a firmware for USB connection, and (v) a USB foot pedal to confirm rotation, (vi) test software and documentation. The testbed uses available off-the-shelf components, and it is distributed with an open source license, Unity package with cues examples and scripts for running tests with randomized targets and collecting performance data (error count and speed). We evaluated the MR testbed by comparing the Arrow cue (baseline) and two novel designs: Magnifier with a zoomed region and Gestalt leveraging related perception principles. A within-subjects study ($\mathrm{N}=36,180^{\prime \prime}, 18$ọ,$\mathrm{M}=27.58, \pm 3.55$) showed that the Magnifier is the most precise ($p<.001$), while the Gestalt is the fastest ($p<.001$). Moreover, males (higher motor and gaming skills) ($\mathrm{p}<.002, \mathrm{t}=3.89$) resulted in faster ($\mathrm{r}=-0.458, \mathrm{p}<$. 005). Participants who declared with higher gaming skills demonstrated less task load during the experiment ($\mathrm{r}=+0.548, \mathrm{p}<.005$). Overall, the participants slightly preferred the Gestalt (18) over the Magnifier (15), while the Arrow was selected by a few (3). Ultimately, the testbed has proven to be an effective research and evaluation platform for future mixed reality interfaces.

The literature has demonstrated the advantages of Mixed Reality (MR) for product configuration by providing a more engaging and effective end-user experience. While collaborative and remote design tools in MR have been widely explored in previous studies, a noticeable gap remains in the exploration of co-located product configuration for couples. This gap is noteworthy since in many industries, couples (e.g., friends, partners) often make purchasing decisions together in physical retail environments. In this paper, we introduce MR-CoCo, an open MR testbed designed to explore collaborative configurations by co-located couples, both in the role of customers. The testbed is developed in Unity and features: (i) a shared MR space with virtual product 3D model anchoring, (ii) shared visualization of the current configuration, (iii) a versatile UI for selecting configuration areas, (iv) hand gestures for 3D drag and drop of colors and materials from 3D catalog to the product. A case study of the personalization of a sailboat is provided as proof of concept. The user study involved 24 couples (48 participants in total), simulating a purchasing experience and the related configuration using MR-CoCo. We assessed usability through post-experience evaluations, with the System Usability Scale (SUS) and the Co-Presence Configuration Questionnaire (CCQ) to measure collaboration and decision-making. The results demonstrated a high level of usability and perceived quality of collaboration. We also explore guidelines that can be used for remote collaboration applications, enabling configuration across a wide range of industries (e.g., automotive and clothing).

TOTTA outlines the spatial position and rotation guidance of a real/virtual tool (TO) towards a real/virtual target (TA), which is a key task in Mixed reality applications. The task error can have critical consequences regarding safety, performance, and quality, such as surgical implantology or industrial maintenance scenarios. The TOTTA problem lacks a dedicated study and it is scattered in different domains with isolated designs. This work contributes to a systematic review of the TOTTA visual widgets, studying 70 unique designs from 24 papers. TOTTA is commonly guided by the visual overlap -an intuitive, pre-attentive "collimation" feedback- of simple shaped widgets: Box, 3D Axes, 3D Model, 2D Crosshair, Globe, Tetrahedron, Line, Plane. Our research discovers that TO and TA are often represented with the same shape. They are distinguished by topological elements (e.g. edges/vertices/faces), colors, transparency levels, and added. shapes, widget quantity, and size. Meanwhile some designs provide continuous "during manipulation feedback" relative to the distance between TO and TA by text, dynamic color, sonification, and amplified graphical visualization. Some approaches trigger discrete "TA reached feedback" such as color alteration, added sound, TA shape change, and added text. We found the lack of golden standards, including in testing procedures, as current ones are limited to partial sets with different and incomparable setups (different target configurations, avatar, background, etc.). We also found a bias in participants: right-handed, young male, non-color impaired.

Mixed Reality (MR) is proven in the literature to support precise spatial dental drill positioning by superimposing 3D widgets. Despite this, the related knowledge about widget's visual design and interactive user feedback is still limited. Therefore, this study is contributed to by co-designed MR drill tool positioning widgets with two expert dentists and three MR experts. The results of co-design are two static widgets (SWs): a simple entry point, a target axis, and two dynamic widgets (DWs), variants of dynamic error visualization with and without a target axis (DWTA and DWEP). We evaluated the co-designed widgets in a virtual reality simulation supported by a realistic setup with a tracked phantom patient, a virtual magnifying loupe, and a dentist's foot pedal. The user study involved 35 dentists with various backgrounds and years of experience. The findings demonstrated significant results; DWs outperform SWs in positional and rotational precision, especially with younger generations and subjects with gaming experiences. The user preference remains for DWs (19) instead of SWs (16). However, findings indicated that the precision positively correlates with the time trade-off. The post-experience questionnaire (NASA-TLX) showed that DWs increase mental and physical demand, effort, and frustration more than SWs. Comparisons between DWEP and DWTA show that the DW's complexity level influences time, physical and mental demands. The DWs are extensible to diverse medical and industrial scenarios that demand precision.

Drill tool positioning in dental implantology is a challenging task requiring 5DOF precision as the rotation around the tool axis is not influential. This work improves the quasi-static visual elements of the state-of-the-art with a novel Augmented Collimation Widget (ACW), an interactive tool of position and angle error visualization based on the gestalt reification, the human ability to group geometric elements. The user can seek in a quick, pre-attentive way the collimation of five (three positional and two rotational) error component widgets (ECWs), taking advantage of three key aspects: component separation and reification, error visual amplification, and dynamic hiding of the collimated components. We compared the ACW with the golden standard in a within-subjects (N=30) user test using 32 implant targets, measuring the time, error, and usability. ACW performed significantly better in positional (+19%) and angular (+47%) precision accuracy and with less mental demand (-6%) and frustration (-13%), but with an expected increase in task time (+59%) and physical demand (+64%). The interview indicated the ACW as the main preference and aesthetically more pleasant than GSW, candidating it as the new golden standard for implantology, but also for other applications where 5DOF positioning is key.