Gaze correction for home video conferencing Kuster, Claudia; Popa, Tiberiu; Bazin, Jean-Charles ...
ACM transactions on graphics,
11/2012, Letnik:
31, Številka:
6
Journal Article
Recenzirano
Effective communication using current video conferencing systems is severely hindered by the lack of eye contact caused by the disparity between the locations of the subject and the camera. While ...this problem has been partially solved for high-end expensive video conferencing systems, it has not been convincingly solved for consumer-level setups. We present a gaze correction approach based on a single Kinect sensor that preserves both the integrity and expressiveness of the face as well as the fidelity of the scene as a whole, producing nearly artifact-free imagery. Our method is suitable for mainstream home video conferencing: it uses inexpensive consumer hardware, achieves real-time performance and requires just a simple and short setup. Our approach is based on the observation that for our application it is sufficient to synthesize only the corrected face. Thus we render a gaze-corrected 3D model of the scene and, with the aid of a face tracker, transfer the gaze-corrected facial portion in a seamless manner onto the original image.
We consider the flow of marine-terminating outlet glaciers that are laterally confined in a channel of prescribed width. In that case, the drag exerted by the channel side walls on a floating ice ...shelf can reduce extensional stress at the grounding line. If ice flux through the grounding line increases with both ice thickness and extensional stress, then a longer shelf can reduce ice flux by decreasing extensional stress. Consequently, calving has an effect on flux through the grounding line by regulating the length of the shelf. In the absence of a shelf, it plays a similar role by controlling the above-flotation height of the calving cliff. Using two calving laws, one due to Nick et al. (2010) based on a model for crevasse propagation due to hydrofracture and the other simply asserting that calving occurs where the glacier ice becomes afloat, we pose and analyse a flowline model for a marine-terminating glacier by two methods: direct numerical solution and matched asymptotic expansions. The latter leads to a boundary layer formulation that predicts flux through the grounding line as a function of depth to bedrock, channel width, basal drag coefficient, and a calving parameter. By contrast with unbuttressed marine ice sheets, we find that flux can decrease with increasing depth to bedrock at the grounding line, reversing the usual stability criterion for steady grounding line location. Stable steady states can then have grounding lines located on retrograde slopes. We show how this anomalous behaviour relates to the strength of lateral versus basal drag on the grounded portion of the glacier and to the specifics of the calving law used.
Purpose
Neuronavigation systems making use of augmented reality (AR) have been the focus of much research in the last couple of decades. In recent years, there has been considerable interest in using ...mobile devices for AR in the operating room (OR). We propose a complete system that performs real-time AR video augmentation on a mobile device in the context of image-guided neurosurgery.
Methods
MARIN (mobile augmented reality interactive neuronavigation system) improves upon the state of the art in terms of performance, allowing real-time augmentation, and interactivity by allowing users to interact with the displayed data. The system was tested in a user study with 17 subjects for qualitative and quantitative evaluation in the context of target localization and brought into the OR for preliminary feasibility tests, where qualitative feedback from surgeons was obtained.
Results
The results of the user study showed that MARIN performs significantly better in terms of both time (
p
<
0.0004
) and accuracy (
p
<
0.04
) for the task of target localization in comparison with a traditional image-guided neurosurgery (IGNS) navigation system. Further, MARIN AR visualization was found to be more intuitive and allowed users to estimate target depth more easily.
Conclusion
MARIN improves upon previously proposed mobile AR neuronavigation systems with its real-time performance, higher accuracy, full integration in the normal workflow and greater interactivity and customizability of the displayed information. The improvement in efficiency and usability over previous systems will facilitate bringing AR into the OR.
Image-guided surgery (IGS) has allowed for more minimally invasive procedures, leading to better patient outcomes, reduced risk of infection, less pain, shorter hospital stays and faster recoveries. ...One drawback that has emerged with IGS is that the surgeon must shift their attention from the patient to the monitor for guidance. Yet both cognitive and motor tasks are negatively affected with attention shifts. Augmented reality (AR), which merges the realworld surgical scene with preoperative virtual patient images and plans, has been proposed as a solution to this drawback. In this work, we studied the impact of two different types of AR IGS set-ups (mobile AR and desktop AR) and traditional navigation on attention shifts for the specific task of craniotomy planning. We found a significant difference in terms of the time taken to perform the task and attention shifts between traditional navigation, but no significant difference between the different AR set-ups. With mobile AR, however, users felt that the system was easier to use and that their performance was better. These results suggest that regardless of where the AR visualisation is shown to the surgeon, AR may reduce attention shifts, leading to more streamlined and focused procedures.
Al
2O
3 was added as a component of conventional high temperature iron oxide-based water gas shift catalysts. A series of catalysts were prepared with 5–20
wt% Al
2O
3, each with 8
wt% Cr
2O
3, 4
wt% ...CuO, and balance Fe
2O
3. Addition of 10–15
wt% alumina increased the catalyst activity and thermal stability, with approximately 15
wt% alumina addition being optimum.
Alumina (Al
2O
3) was added as a component of conventional iron oxide-based high temperature water gas shift (WGS) catalysts. The catalysts contained Fe–Al–Cr–Cu–O and were synthesized by coprecipitation. A series of catalysts were prepared with 5–50
wt% Al
2O
3, 8
wt% Cr
2O
3, 4
wt% CuO, and the balance Fe
2O
3. One catalyst was prepared in which the chromia was replaced by alumina. All of the catalysts were compared to a reference WGS catalyst (88
wt% FeO
x, 8
wt% Cr
2O
3, and 4
wt% CuO) with no alumina. The catalysts were characterized using temperature programmed reduction (TPR), surface area analysis using nitrogen physisorption, and scanning electron microscopy (SEM) with compositional analysis. The catalysts were also tested kinetically under WGS conditions.
Addition of 10–15
wt% alumina increased the catalyst activity and thermal stability, with approximately 15
wt% alumina addition being optimum, as this catalyst produced a reaction rate (normalized per mass) 74% higher than the reference catalyst. The effect of alumina addition was greater than the surface area increase alone, which suggests that alumina alters the activity of the iron oxide domains, likely through an increase in reducibility, as shown by the TPR results. This synergistic effect was only observed when both alumina and chromia were present. Alumina alone (as a replacement for chromia) was not as an effective stabilizer as chromia. Although both the alumina-containing catalyst (without chromia) and the reference with chromia had similar initial surface areas (∼160
m
2/g), the alumina-containing catalyst retained only 74% as much surface area after reaction. Results from the catalysts with 50
wt% alumina suggest that the loss of catalytic activity is also due to the formation of aluminates.
To dynamically assess for Hill–Sachs engagement with animated 3-dimensional (3D) shoulder models.
We created 3D shoulder models from reconstructed computed tomography (CT) images from a consecutive ...series of patients with recurrent anterior dislocation. They were divided into 2 groups based on the perceived Hill–Sachs severity. For our cohort of 14 patients with recurrent anterior dislocation, 4 patients had undergone osteoarticular allografting of Hill–Sachs lesions and 10 control patients had undergone CT scanning to quantify bone loss but no treatment for bony pathology. A biomechanical analysis was performed to rotate each 3D model using local coordinate systems to the classical vulnerable position of the shoulder (abduction = 90°, external rotation = 0-135°) and through a functional range. A Hill–Sachs lesion was considered “dynamically” engaging if the angle between the lesion’s long axis and anterior glenoid was parallel. Results: In the vulnerable position of the shoulder, none of the Hill–Sachs lesions aligned with the anterior glenoid in any of our patients. However, in our simulated physiological shoulder range, all allograft patients and 70% of controls had positions producing alignment.
The technique offers a visual representation of an engaging Hill–Sachs using 3D-animated reconstructions with open-source software and CT images. In our series of patients, we found multiple shoulder positions that align the Hill–Sachs and glenoid axes that do not necessarily meet the traditional definition of engagement. Identifying all shoulder positions at risk of “engaging,” in a broader physiological range, may have critical implications toward selecting the appropriate surgical management of bony defects.
level III, case-control study.
In image-guided neurosurgery, a registration between the patient and their pre-operative images and the tracking of surgical tools enables GPS-like guidance to the surgeon. However, factors such as ...brainshift, image distortion, and registration error cause the patient-to-image alignment accuracy to degrade throughout the surgical procedure no longer providing accurate guidance. The authors present a gesture-based method for manual registration correction to extend the usage of augmented reality (AR) neuronavigation systems. The authors’ method, which makes use of the touchscreen capabilities of a tablet on which the AR navigation view is presented, enables surgeons to compensate for the effects of brainshift, misregistration, or tracking errors. They tested their system in a laboratory user study with ten subjects and found that they were able to achieve a median registration RMS error of 3.51 mm on landmarks around the craniotomy of interest. This is comparable to the level of accuracy attainable with previously proposed methods and currently available commercial systems while being simpler and quicker to use. The method could enable surgeons to quickly and easily compensate for most of the observed shift. Further advantages of their method include its ease of use, its small impact on the surgical workflow and its small-time requirement.
We propose an optimization-driven approach for automated, physics-based pattern design for tight-fitting clothing. Designing such clothing poses particular challenges since large nonlinear ...deformations, tight contact between cloth and body, and body deformations have to be accounted for. To address these challenges, we develop a computational model based on an embedding of the two-dimensional cloth mesh in the surface of the three-dimensional body mesh. Our Lagrangian-on-Lagrangian approach eliminates contact handling while coupling cloth and body. Building on this model, we develop a physics-driven optimization method based on sensitivity analysis that automatically computes optimal patterns according to design objectives encoding body shape, pressure distribution, seam traction, and other criteria. We demonstrate our approach by generating personalized patterns for various body shapes and a diverse set of garments with complex pattern layouts.
We introduce a purely passive facial capture approach that uses only an array of video cameras, but requires no template facial geometry, no special makeup or markers, and no active lighting. We ...obtain initial geometry using multi-view stereo, and then use a novel approach for automatically tracking texture detail across the frames. As a result, we obtain a high-resolution sequence of compatibly triangulated and parameterized meshes. The resulting sequence can be rendered with dynamically captured textures, while also consistently applying texture changes such as virtual makeup.
Individuals with a non-syndromic family history of colorectal cancer are known to have an increased risk. There is an opportunity to prevent early-onset colorectal cancer (age less than 50 years) ...(EOCRC) in this population. The aim was to explore the proportion of EOCRC that is preventable due to family history of colorectal cancer.
This was a retrospective multicentre European study of patients with non-hereditary EOCRC. The impact of the European Society of Gastrointestinal Endoscopy (ESGE), U.S. Multi-Society Task Force (USMSTF), and National Comprehensive Cancer Network (NCCN) guidelines on prevention and early diagnosis was compared. Colorectal cancer was defined as potentially preventable if surveillance colonoscopy would have been performed at least 5 years before the age of diagnosis of colorectal cancer, and diagnosed early if colonoscopy was undertaken between 1 and 4 years before the diagnosis.
Some 903 patients with EOCRC were included. Criteria for familial colorectal cancer risk in ESGE, USMSTF, and NCCN guidelines were met in 6.3, 9.4, and 30.4 per cent of patients respectively. Based on ESGE, USMSTF, and NCCN guidelines, colorectal cancer could potentially have been prevented in 41, 55, and 30.3 per cent of patients, and diagnosed earlier in 11, 14, and 21.1 per cent respectively. In ESGE guidelines, if surveillance had started 10 years before the youngest relative, there would be a significant increase in prevention (41 versus 55 per cent; P = 0.010).
ESGE, USMSTF, and NCCN criteria for familial colorectal cancer were met in 6.3, 9.4, and 30.4 per cent of patients with EOCRC respectively. In these patients, early detection and/or prevention could be achieved in 52, 70, and 51.4 per cent respectively. Early and accurate identification of familial colorectal cancer risk and increase in the uptake of early colonoscopy are key to decreasing familial EOCRC.
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