Christian Hirt

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Hirt

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Christian

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0000-0003-4396-1496

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Publications 1 - 10 of 22

Redirected Walking in Overlapping Rooms
Lutfallah, Mathieu; Hirt, Christian; Gorobets, Valentina; et al. (2023)
SIGGRAPH '23: ACM SIGGRAPH 2023 Posters
Walking in larger virtual environments than the physical one can lead to collisions with physical boundaries. Multiple locomotion techniques like Redirected Walking (RDW) and Overlapping Architecture (OA) aim to overcome this limitation. Combining these two has yet to be investigated in large physical spaces with resets. In this work, a hybrid locomotion method was implemented that combines RDW and OA. A user study was conducted where participants collected items in a virtual environment with multiple rooms. The study showed that the distance walked between resets was increased substantially, thus showing the solid advantages of combining OA and RDW.
Experiential Training of Hand Hygiene Using Virtual Reality
Clack, Lauren; Hirt, Christian; Kunz, Andreas; et al. (2021)
Intelligent Systems Reference Library ~ Recent Advances in Technologies for Inclusive Well-Being
Hand hygiene is widely recognized as an important measure to prevent the transmission of microorganisms that may be involved in healthcare-associated infections. Yet correct hand hygiene remains challenging and healthcare providers struggle to improve adherence. While seemingly straightforward, performing hand hygiene at the right indication using the right technique becomes difficult within the context of complex work processes. We believe that an important barrier to hand hygiene is the invisible nature of microorganisms and delayed expression of healthcare associated infections. This delayed or missing feedback makes it difficult to associate unsafe behaviors with their negative consequences. In this chapter, we describe an application of experiential learning theory to guide the development of a virtual reality hand hygiene trainer in which visual feedback about microorganism transmission and infectious outcomes are introduced in the virtual environment. With this immersive trainer, our aim is to enhance experiential learning and increase intrinsic motivation to perform hand hygiene.
Stress generation and non-intrusive measurement in virtual environments using eye tracking
Hirt, Christian; Eckard, Marcel; Kunz, Andreas (2020)
Journal of Ambient Intelligence and Humanized Computing
In real life, it is well understood how stress can be induced and how it is measured. While Virtual Reality (VR) applications can resemble such stress inducers, it is still an open question if and how stress can be measured in a non-intrusive way during VR exposure. Usually, the quality of VR applications is estimated by user acceptance in the form of presence. Presence itself describes the individual’s acceptance of a virtual environment as real and is measured by specific questionnaires. Accordingly, it is expected that stress strongly affects this presence and thus also the quality assessment. Consequently, identifying the stress level of a VR user may enable content creators to engage users more immersively by adjusting the virtual environment to the measured stress. In this paper, we thus propose to use a commercially available eye tracking device to detect stress while users are exploring a virtual environment. We describe a user study in which a VR task was implemented to induce stress, while users’ pupil diameter and pulse were measured and evaluated against a self-reported stress level. The results show a statistically significant correlation between self-reported stress and users’ pupil dilation and pulse, indicating that stress measurements can indeed be conducted during the use of a head-mounted display. If this indication can be successfully proven in a larger scope, it will open up a new era of affective VR applications using individual and dynamic adjustments in the virtual environment.
Virtual reality training platform for a computer numerically controlled grinding machine tool
Hirt, Christian; Spahni, Martina; Kompis, Yves; et al. (2021)
International Journal of Mechatronics and Manufacturing Systems
In-depth training of machine tool (MT) operators is crucial to avoid machine damage due to faulty operation. However, machine-hours are costly and during the training, the MT is unavailable for regular production purposes. Here, virtual real-size models offer a solution by providing basic operation principles to future operators. In this context, it is yet unknown whether a virtual teaching enhanced by real walking is similar to a real teaching scenario regarding the learning efficiency and long-term memory retention. This paper describes a study comparing the learning efficiency of a virtual training session with traditional instructions on a real MT. The learning success of both training groups is objectively and subjectively assessed on a realMTa week later. In this assessment, the task completion time and the number of errors are recorded. We observed that the virtually taught group slightly outperformed trainees taught in reality regarding both objective measurements.
Eye Gaze Tracking for Detecting Non-verbal Communication in Meeting Environments
Dhingra, Naina; Hirt, Christian; Angst, Manuel; et al. (2020)
Proceedings of the 15th International Joint Conference on Computer Vision, Imaging and Computer Graphics Theory and Applications
Non-verbal communication in a team meeting is important to understand the essence of the conversation. Among other gestures, eye gaze shows the focus of interest on a common workspace and can also be used for an interpersonal synchronisation. If this non-verbal information is missing and or cannot be perceived by blind and visually impaired people (BVIP), they would lack important information to get fully immersed in the meeting and may feel alienated in the course of the discussion. Thus, this paper proposes an automatic system to track where a sighted person is gazing at. We use the open source software 'OpenFace' and develop it as an eye tracker by using a support vector regressor to make it work similarly to commercially available expensive eye trackers. We calibrate OpenFace using a desktop screen with a 2 3 box matrix and conduct a user study with 28 users on a big screen (161.7 cm x 99.8 cm x 11.5 cm) with a 1 x 5 box matrix. In this user study, we compare the results of our developed algorithm for OpenFace to an SMI RED 250 eye tracker. The results showed that our work achieved an overall relative accuracy of 58.54%.
The Chaotic Behavior of Redirection – Revisiting Simulations in Redirected Walking
Hirt, Christian; Kompis, Yves; Holz, Christian; et al. (2022)
2022 IEEE Conference on Virtual Reality and 3D User Interfaces (VR)
Redirected Walking (RDW) is a common technique leveraged to allow real walking for exploring large virtual environments in constrained physical tracking spaces. Effective RDW is challenging due to its complexity and disturbance factors (e.g., spontaneous user behavior). Existing techniques range from combinations of simple motion scaling to more elaborate curvature injections and reactive, predictive, or scripted steering concepts. However, many of these approaches were evaluated in simulation only, and researchers argued that the findings would translate to real scenarios to motivate the effectiveness of their algorithms. Using the Redirected Walking Toolkit and its virtual path generator, a randomized waypoint-based path generator has been common practice, although its built-in simplifications assume sequential user behavior regarding translation and rotation. In this paper, we argue that pure simulation-based evaluations employing such simplified path generators require critical reflection. We demonstrate RDW simulations that show the chaotic process fundamental to RDW, in which altering the initial user’s position by mere millimeters can drastically change the resulting steering behavior. This insight suggests that RDWis more sensitive to the underlying data than previously assumed. Thus, we rigorously analyze the influence of commonly used synthetically generated paths on multiple state-of-the-art steering concepts and compare them against previously recorded real paths.
Emotion Recognition - A Tool to Improve Meeting Experience for Visually Impaired
Lutfallah, Mathieu; Käch, Benno; Hirt, Christian; et al. (2022)
Lecture Notes in Computer Science ~ Computers Helping People with Special Needs
Facial expressions play an important role in human communication since they enrich spoken information and help convey additional sentiments e.g. mood. Among others, they non-verbally express a partner’s agreement or disagreement to spoken information. Further, together with the audio signal, humans can even detect nuances of changes in a person’s mood. However, facial expressions remain inaccessible to the blind and visually impaired, and also the voice signal alone might not carry enough mood information. Emotion recognition research mainly focused on detecting one of seven emotion classes. Such emotions are too detailed, and having an overall impression of primary emotional states such as positive, negative, or neutral is more beneficial for the visually impaired person in a lively discussion within a team. Thus, this paper introduces an emotion recognition system that allows a real-time detection of the emotions “agree”, “neutral”, and “disagree”, which are seen as the most important ones during a lively discussion. The proposed system relies on a combination of neural networks that allow extracting emotional states while leveraging the temporal information from videos.
SF3B1 facilitates HIF1-signaling and promotes malignancy in pancreatic cancer
Simmler, Patrik; Cortijo, Cédric; Koch, Lisa Maria; et al. (2022)
Cell Reports
Mutations in the splicing factor SF3B1 are frequently occurring in various cancers and drive tumor progression through the activation of cryptic splice sites in multiple genes. Recent studies also demonstrate a positive correlation between the expression levels of wild-type SF3B1 and tumor malignancy. Here, we demonstrate that SF3B1 is a hypoxia-inducible factor (HIF)-1 target gene that positively regulates HIF1 pathway activity. By physically interacting with HIF1α, SF3B1 facilitates binding of the HIF1 complex to hypoxia response elements (HREs) to activate target gene expression. To further validate the relevance of this mechanism for tumor progression, we show that a reduction in SF3B1 levels via monoallelic deletion of Sf3b1 impedes tumor formation and progression via impaired HIF signaling in a mouse model for pancreatic cancer. Our work uncovers an essential role of SF3B1 in HIF1 signaling, thereby providing a potential explanation for the link between high SF3B1 expression and aggressiveness of solid tumors.
Remote Cross-platform Instructions between MR and VR
Lutfallah, Mathieu; Gini, Tamara; Hirt, Christian; et al. (2023)
2023 International Conference on Cyberworlds (CW)
This paper introduces a collaboration setting where an expert in VR gives instructions to a technician using MR being in front of the real object. For this study, we develop a system in which users communicate while building a specific structure using Lego Duplo blocks. Here, only the expert knows the final configuration and instructs the technician equipped with an MR headset about the assembly. Four communication methods are evaluated: voice chat, avatars, the possibility of moving virtual blocks similar to the real ones, and an arrow functionality. This work proves the usefulness of such an VR/MR instruction system and provides insights into the advantages of each proposed communication method.
Investigation into Recording, Replay and Simulation of Interactions in Virtual Reality
Siebenmann, Michael; Lutfallah, Mathieu; Jetter, Dominic; et al. (2024)
ICVARS '24: Proceedings of the 2024 8th International Conference on Virtual and Augmented Reality Simulations
In this study, we introduce an authoring toolkit enabling both experts and trainees to record their actions in a virtual environment, streamlining the creation of training procedures and the evaluation of trainee actions. The toolkit was developed using two distinct methods: a state-based and an input-based approach. Within a virtual testing environment, we compared these methods across a range of interactions, focusing on three performance metrics: memory footprint, performance overhead, and replay accuracy. Contrary to initial predictions, the state-based method, after optimization, consumed less memory than the input-based approach. Both methods maintained low performance overheads during recording and replaying phases. Notably, the state-based approach achieved superior replay accuracy. In contrast, the input-based method displayed varying degrees of replay inaccuracies, partially attributable to the non-deterministic physics engine of the Unity development platform.

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Christian Hirt

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