224 research outputs found

    Scalable partitioning for parallel position based dynamics

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    We introduce a practical partitioning technique designed for parallelizing Position Based Dynamics, and exploiting the ubiquitous multi-core processors present in current commodity GPUs. The input is a set of particles whose dynamics is influenced by spatial constraints. In the initialization phase, we build a graph in which each node corresponds to a constraint and two constraints are connected by an edge if they influence at least one common particle. We introduce a novel greedy algorithm for inserting additional constraints (phantoms) in the graph such that the resulting topology is q-colourable, where ˆ qˆ ≥ 2 is an arbitrary number. We color the graph, and the constraints with the same color are assigned to the same partition. Then, the set of constraints belonging to each partition is solved in parallel during the animation phase. We demonstrate this by using our partitioning technique; the performance hit caused by the GPU kernel calls is significantly decreased, leaving unaffected the visual quality, robustness and speed of serial position based dynamics

    Upgrade of foss date plug-in: Implementation of a new radargrammetric DSM generation capability

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    Synthetic Aperture Radar (SAR) satellite systems may give important contribution in terms of Digital Surface Models (DSMs) generation considering their complete independence from logistic constraints on the ground and weather conditions. In recent years, the new availability of very high resolution SAR data (up to 20 cm Ground Sample Distance) gave a new impulse to radargrammetry and allowed new applications and developments. Besides, to date, among the software aimed to radargrammetric applications only few show as free and open source. It is in this context that it has been decided to widen DATE (Digital Automatic Terrain Extractor) plug-in capabilities and additionally include the possibility to use SAR imagery for DSM stereo reconstruction (i.e. radargrammetry), besides to the optical workflow already developed. DATE is a Free and Open Source Software (FOSS) developed at the Geodesy and Geomatics Division, University of Rome "La Sapienza", and conceived as an OSSIM (Open Source Software Image Map) plug-in. It has been developed starting from May 2014 in the framework of 2014 Google Summer of Code, having as early purpose a fully automatic DSMs generation from high resolution optical satellite imagery acquired by the most common sensors. Here, the results achieved through this new capability applied to two stacks (one ascending and one descending) of three TerraSAR-X images each, acquired over Trento (Northern Italy) testfield, are presented. Global accuracies achieved are around 6 metres. These first results are promising and further analysis are expected for a more complete assessment of DATE application to SAR imagery

    High resolution satellite imagery orientation accuracy assessment by leave-one-out method: accuracy index selection and accuracy uncertainty

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    The Leave-one-out cross-validation (LOOCV) was recently applied to the evaluation of High Resolution Satellite Imagery orientation accuracy and it has proven to be an effective method alternative with respect to the most common Hold-out-validation (HOV), in which ground points are split into two sets, Ground Control Points used for the orientation model estimation and Check Points used for the model accuracy assessment. On the contrary, the LOOCV applied to HRSI implies the iterative application of the orientationmodel using all the known ground points as GCPs except one, different in each iteration, used as a CP. In every iteration the residual between imagery derived coordinates with respect to CP coordinates (prediction error of the model on CP coordinates) is calculated; the overall spatial accuracy achievable from the oriented image may be estimated by computing the usual RMSE or, better, a robust accuracy index like the mAD (median Absolute Deviation) of prediction errors on all the iterations. In this way it is possible to overcome some drawbacks of the HOV: LOOCVis a reliable and robustmethod, not dependent on a particular set of CPs and on possible outliers, and it allows us to use each known ground point both as a GCP and as a CP, capitalising all the available ground information. This is a crucial problem in current situations, when the number of GCPs to be collected must be reduced as much as possible for obvious budget problems. The fundamentalmatter to deal with was to assess howwell LOOCVindexes (mADand RMSE) are able to represent the overall accuracy, that is howmuch they are stable and close to the corresponding HOV RMSE assumed as reference. Anyway, in the first tests the indexes comparison was performed in a qualitative way, neglecting their uncertainty. In this work the analysis has been refined on the basis of Monte Carlo simulations, starting from the actual accuracy of ground points and images coordinates, estimating the desired accuracy indexes (e.g. mAD and RMSE) in several trials, computing their uncertainty (standard deviation) and accounting for them in the comparison. Tests were performed on a QuickBird Basic image implementing an ad hoc procedure within the SISAR software developed by the Geodesy and Geomatics Team at the Sapienza University of Rome. The LOOCV method with accuracy evaluated by mAD seemed promising and useful for practical case

    Geometric potential of cartosat-1 stereo imagery

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    Cartosat-1 satellite, launched by Department of Space (DOS), Government of India, is dedicated to stereo viewing for large scale mapping and terrain modelling applications. This stereo capability fills the limited capacity of very high resolution satellites for three-dimensional point determination and enables the generation of detailed digital elevation models (DEMs) not having gaps in mountainous regions like for example the SRTM height model.The Cartosat-1 sensor offers a resolution of 2.5m GSD in panchromatic mode. One CCD-line sensor camera is looking with a nadir angle of 26' in forward direction, the other 5' aft along the track. The Institute "Area di Geodesia e Geomatica"-Sapienza Università di Roma and the Institute of Photogrammetry and Geoinformation, Leibniz University Hannover participated at the ISPRS-ISRO Cartosat-1 Scientific Assessment Programme (CSAP), in order to investigate the generation of Digital Surface Models (DSMs) from Cartosat-1 stereo scenes. The aim of this work concerns the orientation of Cartosat-1 stereo pairs, using the given RPCs improved by control points and the definition of an innovative model based on geometric reconstruction, that is used also for the RPC extraction utilizing a terrain independent approach. These models are implemented in the scientific software (SISAR-Software per Immagini Satellitari ad Alta Risoluzione) developed at Sapienza Università di Roma. In this paper the SISAR model is applied to different stereo pairs (Castelgandolfo and Rome) and to point out the effectiveness of the new model, SISAR results are compared with the corresponding ones obtained by the software OrthoEngine 10.0 (PCI Geomatica).By the University of Hannover a similar general satellite orientation program has been developed and the good results, achieved by bias corrected sensor oriented RPCs, for the test fields Mausanne (France) and Warsaw (Poland) have been described.For some images, digital height models have been generated by automatic image matching with least squares method, analysed in relation to given reference height models. For the comparison with the reference DEMs the horizontal fit of the height models to each other has been checked by adjustment

    Fast Analytical Motion Blur with Transparency

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    We introduce a practical parallel technique to achieve real-time motion blur for textured and semi-transparent triangles with high accuracy using modern commodity GPUs. In our approach, moving triangles are represented as prisms. Each prism is bounded by the initial and final position of the triangle during one animation frame and three bilinear patches on the sides. Each prism covers a number of pixels for a certain amount of time according to its trajectory on the screen. We efficiently find, store and sort the list of prisms covering each pixel including the amount of time the pixel is covered by each prism. This information, together with the color, texture, normal, and transparency of the pixel, is used to resolve its final color. We demonstrate the performance, scalability, and generality of our approach in a number of test scenarios, showing that it achieves a visual quality practically indistinguishable from the ground truth in a matter of just a few milliseconds, including rendering of textured and transparent objects. A supplementary video has been made available online

    Method for interactive, real-time animation of soft body dynamics

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    There is presented a method for interactive, real-time animation of soft body dynamics , comprising the steps of: providing a 3D model of a soft body, the model comprising a set of vertices connected by edges ; defining a set of physical constraints between vertices in the 3D model , the set of constraints forming a system of linear equations comprising a set of unknowns representing the positions of the vertices ; applying a Brooks-Vizing node coloring algorithm in order to partition the system of linear equations into a set of partitions each including an independent subset of unknowns; for each partition , applying a Gauss - Seidel based solver in parallel in order to determine an approximation of the unknowns ; and using the determined approximation of the unknowns to update the 3D model . There is also pre sented an animation system configured to perform the above-described method

    Orientation models of optical High Resolution Satellite Imagery: definition, implementation and validation of original algorithms

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    High resolution satellite imagery became available to civil users in 1999 with the launch of Ikonos, the first civil satellite offering a spatial resolution of 1 m. Since then other high resolution satellites have been launched, among which there are EROS-A (1.8 m), QuickBird (0.61 m), Orbview-3 (1 m), EROS-B (0.7 m), Worldview-1 (0.5 m) and GeoEye-1 (0.41 m), with many others being planned to launch in the near future. High resolution satellite imagery is now available in different formats and processing levels at an affordable price, so that they already represent a possible alternative to aerial imagery, for cartographic applications and orthophoto production, especially for areas where the organization of photogrammetric surveying may be critical. Moreover, an increasing demand for terrain modelling exists so that almost all the satellites have along-track stereo acquisition capability. Many new satellites dedicated to stereo viewing, for example Cartosat-1 (2.5 m), have been launched. This enables the generation of Digital Elevation Models (DEMs) and Digital Surface Models (DSMs), and also for 3D feature extraction (e.g. for city modelling). The geomatic utilizations of satellite imagery for cartographic applications and terrain modelling require a high level geometric correction through image orientation. Some fundamental features related to the sensor models and their parameters estimation, both for single images and stereopairs orientation, were addressed and some real applications were discussed. In details, they were concerned both physical sensor models (also called rigorous models) and generalized sensor models (also called RPC models) for the orientation of basic images (level 1A) and of the image projected onto a specific object surface (usually an expanded ellipsoid derived from the WGS84) (level 1B). As regards the rigorous models, a thorough investigation of the fundamentals of their functional model was developed and the problem of parameters estimability was concerned, proposing a solution based on SVD and QR decomposition. RPC models were discussed not only with respect possible refinements by zero and first order transformations but also (and mainly) with respect the RPCs generation, based on previously established rigorous model; thanks to SVD and QR decomposition, it was showed that many RPCs are not estimable parameters, therefore they are not necessary to obtain the best achievable accuracy level. Real applications demonstrated that rigorous and RPC models both for Level 1A and Level 1B imagery can provide orientation accuracy at 1-1.5 pixel level in the horizontal components, and at 1-2 pixel level in the height for stereopairs (even better with Cartosat-1 and slightly worse with EROS-1)

    Orientation models of optical High Resolution Satellite Imagery: definition, implementation and validation of original algorithms

    Get PDF
    High resolution satellite imagery became available to civil users in 1999 with the launch of Ikonos, the first civil satellite offering a spatial resolution of 1 m. Since then other high resolution satellites have been launched, among which there are EROS-A (1.8 m), QuickBird (0.61 m), Orbview-3 (1 m), EROS-B (0.7 m), Worldview-1 (0.5 m) and GeoEye-1 (0.41 m), with many others being planned to launch in the near future. High resolution satellite imagery is now available in different formats and processing levels at an affordable price, so that they already represent a possible alternative to aerial imagery, for cartographic applications and orthophoto production, especially for areas where the organization of photogrammetric surveying may be critical. Moreover, an increasing demand for terrain modelling exists so that almost all the satellites have along-track stereo acquisition capability. Many new satellites dedicated to stereo viewing, for example Cartosat-1 (2.5 m), have been launched. This enables the generation of Digital Elevation Models (DEMs) and Digital Surface Models (DSMs), and also for 3D feature extraction (e.g. for city modelling). The geomatic utilizations of satellite imagery for cartographic applications and terrain modelling require a high level geometric correction through image orientation. Some fundamental features related to the sensor models and their parameters estimation, both for single images and stereopairs orientation, were addressed and some real applications were discussed. In details, they were concerned both physical sensor models (also called rigorous models) and generalized sensor models (also called RPC models) for the orientation of basic images (level 1A) and of the image projected onto a specific object surface (usually an expanded ellipsoid derived from the WGS84) (level 1B). As regards the rigorous models, a thorough investigation of the fundamentals of their functional model was developed and the problem of parameters estimability was concerned, proposing a solution based on SVD and QR decomposition. RPC models were discussed not only with respect possible refinements by zero and first order transformations but also (and mainly) with respect the RPCs generation, based on previously established rigorous model; thanks to SVD and QR decomposition, it was showed that many RPCs are not estimable parameters, therefore they are not necessary to obtain the best achievable accuracy level. Real applications demonstrated that rigorous and RPC models both for Level 1A and Level 1B imagery can provide orientation accuracy at 1-1.5 pixel level in the horizontal components, and at 1-2 pixel level in the height for stereopairs (even better with Cartosat-1 and slightly worse with EROS-1)

    Making headway: an exploratory study of the perceptions of and composition of NCAA Division I concussion management plans

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    Concussion in sport has attracted substantial attention from the media and the public. Stories depicting the fatality of concussion have raised concern for athletes. It is estimated that 300,000 sport-related traumatic brain injuries occur in the United States annually. Research shows that the frequency and severity of the brain impact leads to symptoms that can last for as little as several hours to a lifetime. Resulting from the increased awareness and knowledge of concussions in addition to the influence of litigation, the National Collegiate Athletic Association (NCAA) furthered its dedication to the health of student-athletes in 2010 by mandating that all member institutions must have written concussion management plans on file. The purpose of this study was to analyze the perceptions of Division I athletic administrators and sports medicine personnel of concussion management plans and to determine the composition of those plans

    Interactive Assembly and Animation of 3D Digital Garments

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    We present a novel real-time tool for sewing together 2D patterns, enabling quick assembly of visually plausible, interactively animated garments for virtual characters. The process is assisted by ad-hoc visual hints and allows designers to import 2D patterns from any CAD-tool, connect them using seams around a 3D character with any body type, and assess the overall quality during the character animation. The cloth is numerically simulated including robust modeling of contact of the cloth with itself and with the character\u27s body. Overall, our tool allows for fast prototyping of virtual garments, achieving immediate feedback on their behaviour and visual quality on an animated character, in effect speeding up the content production pipeline for visual effects applications involving clothed characters
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