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Sharma, Rajat; Schwandt, Tobias; Kunert, Christian; Urban, Steffen; Broll, Wolfgang;
Point cloud upsampling and normal estimation using deep learning for robust surface reconstruction. - In: VISIGRAPP 2021. - [Sétubal] : SCITEPRESS - Science and Technology Publications, Lda., (2021), S. 70-79

The reconstruction of real-world surfaces is on high demand in various applications. Most existing reconstruction approaches apply 3D scanners for creating point clouds which are generally sparse and of low density. These points clouds will be triangulated and used for visualization in combination with surface normals estimated by geometrical approaches. However, the quality of the reconstruction depends on the density of the point cloud and the estimation of the surface normals. In this paper, we present a novel deep learning architecture for point cloud upsampling that enables subsequent stable and smooth surface reconstruction. A noisy point cloud of low density with corresponding point normals is used to estimate a point cloud with higher density and appendant point normals. To this end, we propose a compound loss function that encourages the network to estimate points that lie on a surface including normals accurately predicting the orientation of the surface. Our results show t he benefit of estimating normals together with point positions. The resulting point cloud is smoother, more complete, and the final surface reconstruction is much closer to ground truth.



Schwandt, Tobias;
High-quality illumination of virtual objects based on an environment estimation in mixed reality applications. - Wiesbaden : Springer Vieweg, 2021. - xxvii, 122 Seiten. . - (Research)
Technische Universität Ilmenau, Dissertation 2021

ISBN 978-3-658-35191-5

Die Visualisierung virtueller Objekte in der Realität erfolgt bei vielen Anwendungen oftmals durch eine vereinfachte Darstellung ohne Bezug zur umliegenden Umgebung. Dabei ist die nahtlose Verschmelzung der virtuellen und realen Umgebung in vielen Bereichen ein wesentlicher Faktor, der insbesondere bei der Beleuchtungsberechnung in gemischten Realitäten von großer Bedeutung ist. Aktuelle Ansätze legen den Fokus auf Approximationen, welche eine Berechnung der diffusen Beleuchtung ermöglichen, wobei die Darstellung glänzender Beleuchtungseigenschaften vernachlässigt wird. Das Ziel dieser Arbeit ist eine Visualisierung von spiegelnden Oberflächen in erweiterten Realitäten zu ermöglichen. Um dieses Ziel zu erreichen werden verschiedene Verfahren aufgezeigt, die eine hochwertige Darstellung virtueller Objekte in Echtzeit ermöglichen, wobei der Fokus auf der Verwendung üblicher Hardware wie Kameras, Sensoren in mobilen Endgeräten und teilweise Tiefensensoren liegt. Das erste Verfahren verwendet das aktuelle Kamerabild zur Rekonstruktion einer 360-Grad Beleuchtung durch die Transformation des Bildes auf eine Würfelkarte. Anschließend wird dieser Ansatz durch ein Stitching erweitert, bei dem das aktuelle Bild zusammen mit der Position und Rotation der Kamera genutzt wird, um eine Umgebungsbeleuchtung zu erstellen. Dabei von der Kamera nicht erfasste Bereiche werden durch ein semantisches Inpainting, basierend auf einem neuronalen Netz, aufgefüllt. Hierdurch kann das komplette Umgebungslicht approximiert werden, welches die Darstellung detaillierter Reflexionen ermöglicht. Die Ergebnisse der Ansätze zeigen neuartige Möglichkeiten, geometrische Formen mit glänzenden Oberflächen in die reale Umgebung einzubetten und bietet im Vergleich zu bestehenden Methoden einen höheren Detailgrad in den Reflexionen. Alle Ansätze sind für eine Verwendung auf mobilen Endgeräten konzipiert, wodurch neue Möglichkeiten für verschiedene Einsatz- und Anwendungsbereiche der erweiterten Realität existieren.



Gerhardt, Christoph; Broll, Wolfgang;
Neural network-based traffic sign recognition in 360˚ images for semi-automatic road maintenance inventory. - In: 2020 IEEE 23rd International Conference on Intelligent Transportation Systems (ITSC). - [Piscataway, NJ] : IEEE, (2020), insges. 7 S.

https://doi.org/10.1109/ITSC45102.2020.9294610
Elbehery, Mostafa; Weidner, Florian; Broll, Wolfgang;
Haptic space: the effect of a rigid hand representation on presence when interacting with passive haptics controls in VR. - In: 19th International Conference on Mobile and Ubiquitous Multimedia : proceedings : Nov 22 - Nov 25, 2020, Essen, Germany.. - New York, New York : The Association for Computing Machinery, (2020), S. 245-253

Many virtual reality (VR) applications rely on passive haptics where virtual objects have a real counterpart that provides tactile feedback. In addition to that, many VR applications do not provide accurate hand representations, especially when there is a high chance of occlusion as this makes vision-based tracking problematic. Hence, we investigated how a simple hand representation affects user experience and presence when interacting with passive haptic controls in a virtual environment. We report on a between-subject user study where N = 45 participants experienced one of three conditions (no hands at all, hands represented as a rigid 3D model, and hands represented as a rigid 3D model with a snapping mechanism). Our results indicate that a simple hand representation using a 3D model of hands paired with a snapping mechanism significantly increases presence and user experience. That indicates that this simple and low-cost technique is effective to improve the VE as a whole. This, in return, provides a chance for improvement for many VR applications with passive haptics.



https://doi.org/10.1145/3428361.3428388
Mori, Shohei; Erat, Okan; Broll, Wolfgang; Saito, Hideo; Schmalstieg, Dieter; Kalkofen, Denis;
InpaintFusion: incremental RGB-D inpainting for 3D scenes. - In: IEEE transactions on visualization and computer graphics : TVCG.. - New York, NY : IEEE, ISSN 1941-0506, Bd. 26 (2020), 10, S. 2994-3007

State-of-the-art methods for diminished reality propagate pixel information from a keyframe to subsequent frames for real-time inpainting. However, these approaches produce artifacts, if the scene geometry is not sufficiently planar. In this article, we present InpaintFusion, a new real-time method that extends inpainting to non-planar scenes by considering both color and depth information in the inpainting process. We use an RGB-D sensor for simultaneous localization and mapping, in order to both track the camera and obtain a surfel map in addition to RGB images. We use the RGB-D information in a cost function for both the color and the geometric appearance to derive a global optimization for simultaneous inpainting of color and depth. The inpainted depth is merged in a global map by depth fusion. For the final rendering, we project the map model into image space, where we can use it for effects such as relighting and stereo rendering of otherwise hidden structures. We demonstrate the capabilities of our method by comparing it to inpainting results with methods using planar geometric proxies.



https://doi.org/10.1109/TVCG.2020.3003768
Weidner, Florian; Broll, Wolfgang;
Stereoscopic 3D dashboards : an investigation of performance, workload, and gaze behavior during take-overs in semi-autonomous driving. - In: Personal and ubiquitous computing : PUC.. - London : Springer, ISSN 1617-4917, (2020), insges. 23 S.
- Published: 25 August 2020

When operating a conditionally automated vehicle, humans occasionally have to take over control. If the driver is out of the loop, a certain amount of time is necessary to gain situation awareness. This work evaluates the potential of stereoscopic 3D (S3D) dashboards for presenting smart S3D take-over-requests (TORs) to support situation assessment. In a driving simulator study with a 4 × 2 between-within design, we presented 3 smart TORs showing the current traffic situation and a baseline TOR in 2D and S3D to 52 participants doing the n-back task. We further investigate if non-standard locations affect the results. Take-over performance indicates that participants looked at and processed the TORs' visual information and by that, could perform more safe take-overs. S3D warnings in general, as well as warnings appearing at the participants focus of attention and warnings at the instrument cluster, performed best. We conclude that visual warnings, presented on an S3D dashboard, can be a valid option to support take-over while not increasing workload. We further discuss participants gaze behavior in the context of visual warnings for automotive user interfaces.



https://doi.org/10.1007/s00779-020-01438-8
Schwandt, Tobias; Kunert, Christian; Broll, Wolfgang;
Environment estimation for glossy reflections in mixed reality applications using a neural network. - In: Special Issue on Cyberworlds and Cybersecurity. - Berlin : Springer, (2020), S. 26-42

Köhler, Carolin; Weidner, Florian; Broll, Wolfgang;
AR training for paragliding pilots: an investigation of user experience and requirements. - In: 2019 21st Symposium on Virtual and Augmented Reality : SVR 2019 : Rio de Janeiro, Brazil, 28-31 October 2019 : proceedings.. - Piscataway, NJ : IEEE, (2019), S. 92-101

https://doi.org/10.1109/SVR.2019.00030
Kunert, Christian; Schwandt, Tobias; Broll, Wolfgang;
An efficient diminished reality approach using real-time surface reconstruction. - In: 2019 International Conference on Cyberworlds : CW 2019 : 2-4 October 2019, Kyoto, Japan : proceedings.. - Piscataway, NJ : IEEE, (2019), S. 9-16

https://doi.org/10.1109/CW.2019.00010
Weidner, Florian; Broll, Wolfgang;
Interact with your car: a user-elicited gesture set to inform future in-car user interfaces. - In: MUM 2019 : 18th International Conference on Mobile and Ubiquitous Multimedia : proceedings : Nov 26 - Nov 29, 2018, Pisa, Italy.. - New York, New York : The Association for Computing Machinery, Inc., (2019), article no. 11, 12 Seiten

https://doi.org/10.1145/3365610.3365625