Rafael Alves Roberto

Challenges in 3D Reconstruction from Images for Difficult Large-Scale Objects: A Study on the Modeling of Electrical Substations

In recent years, 3D reconstruction from images has played a major role in computer vision with a lot of improvements regarding both quality and performance. One of its main uses is the generation of 3D models of objects that are difficult to modeling. In the electrical sector, 3D reconstruction from images shows itself as a candidate to be used in specific scenarios with the advantage of its low price compared to laser scanning techniques. In fact, there are many industrial applications that can use the power of 3D reconstruction from images but no work has focused more deeply on their requirements yet. This paper analyzes the advantages and drawbacks in using 3D reconstruction from image techniques and tools in the uncontrolled environment of an electrical substation from the scenario characteristics and tools limitations points of view. Some representative available tools (commercial and academic) where evaluated and the relationship between scenario/object characteristics and reconstructed model quality could be pointed out for further improvements of the techniques in future work. This results can be used to create industrial applications with large scale difficult objects.

Bare hand natural interaction with augmented objects

In this work in progress we address the problem of interacting with augmented objects. A bare hand tracking technique is developed, which allied to gesture recognition heuristics, enables interaction with augmented objects in an intuitive way. The tracking algorithm uses a flock of features approach that tracks both hands in real time. The interaction occurs by the execution of grasp and release gestures. Physics simulation and photorealistic rendering are added to the pipeline. This way, the tool provides more coherent feedback in order to make the virtual objects look and respond more likely real ones. The pipeline was tested through specific tasks, designed to analyze its performance regarding the easiness of use, precision and response time.

Evaluation of Motion Tracking and Depth Sensing Accuracy of the Tango Tablet

This paper presents an evaluation of the Tango tablet regarding its motion tracking and depth perception capabilities. A methodology for performing such kind of evaluation is proposed. Motion tracking error is assessed in both small workspace and large environments. In the small workspace scenario, the distances reported by the motion tracking system are compared with values measured with the aid of a graph paper. In the large environment condition, the tracking error consists in the difference between initial and final positions given by the system when the device moves around the environment and returns to the same location. Depth sensing precision is evaluated by comparing the 3D coordinates reported by the system of the inner corners of a chessboard pattern with ground truth values obtained from color camera image processing. The results show that Tango tablet sometimes presents large motion tracking errors, which may harm AR experience. In addition, Tango tablet depth sensing presents average error values similar to desktop depth cameras, but it is more sensitive to infrared reflection properties of the objects to be mapped.

ARBlocks: A Concept for a Dynamic Blocks Platform for Educational Activities

This paper describes the concept of a dynamic blocks platform, called ARBlocks, based on projective augmented reality and tangible user interfaces aiming educational activities. In it, the information is displayed by projectors, that exhibit the content only on the blocks using a projector calibration technique and the blocks are tracked through a frame marker. Despite the platform is still under development, some results regarding the frame marker tracking and the projection was achieved.

Markerless tracking system for augmented reality in the automotive industry

Markerless tracking system for augmented reality targeting the automotive sector.System evaluation during the Volkswagen/ISMAR Tracking Challenge 2014.Additional studies in similar competition scenarios created by the authors.System suitable for tracking vehicle exterior / parts and high precision tracking. This paper presents a complete natural feature based tracking system that supports the creation of augmented reality applications focused on the automotive sector. The proposed pipeline encompasses scene modeling, system calibration and tracking steps. An augmented reality application was built on top of the system for indicating the location of 3D coordinates in a given environment which can be applied to many different applications in cars, such as a maintenance assistant, an intelligent manual, and many others. An analysis of the system was performed during the Volkswagen/ISMAR Tracking Challenge 2014, which aimed to evaluate state-of-the-art tracking approaches on the basis of requirements encountered in automotive industrial settings. A similar competition environment was also created by the authors in order to allow further studies. Evaluation results showed that the system allowed users to correctly identify points in tasks that involved tracking a rotating vehicle, tracking data on a complete vehicle and tracking with high accuracy. This evaluation allowed also to understand the applicability limits of texture based approaches in the textureless automotive environment, a problem not addressed frequently in the literature. To the best of the authors knowledge, this is the first work addressing the analysis of a complete tracking system for augmented reality focused on the automotive sector which could be tested and validated in a major benchmark like the Volkswagen/ISMAR Tracking Challenge, providing useful insights on the development of such expert and intelligent systems.

ARBlocks: A projective augmented reality platform for educational activities

This demonstration will allow visitors to use different applications builded for the ARBlocks, a dynamic blocks platform based on projective augmented reality and tangible user interfaces aiming early childhood educational activities. Those applications, along with the platform itself, were designed to be useful tools for educators to teach general subjects for children, such as mathematical and language skills, as well as develop important abilities, like motor coordination and collaboration.

Tracking for mobile devices

Tracking is an important task that is used for several applications, such as navigation assistance and augmented reality. The improvement and popularization of mobile devices in recent years allowed these applications to be executed on such devices. Thus, several tracking techniques proposed lately take into consideration the benefits and limitations of handheld devices. Therefore, the goal of this work is to perform a systematic mapping in order to provide trends and classification regarding the recent publications in the area of tracking for mobile devices. This study collected 2276 papers from three scientific databases using an open-source crawler, from which 360 were selected to be classified according to four properties: tracking type, degree of freedom, tracking platform and research type. The analysis of these data resulted in a map of the research field, which was presented under three perspectives: the distribution and trends over time of each classification property and the relationship between them. Besides the visual map, the full list of classified papers is available through an open-source web-based catalog. The results showed that the number of publications is increasing every year, which shows a growing interest in this field. Moreover, most works use the devices sensors for tracking in location-based applications and almost all of them calculate a 2D or 2D + ? pose. There are also several papers about vision-based techniques to compute the devices pose and in the majority of them a full 6D pose is computed. Beyond that, there is a clear preference for systems that calculate the pose locally on the device and only a few use a remote server to assist in this task. Moreover, more than 92% of all papers propose a new technique or use existing ones to create a solution. Graphical abstractDisplay Omitted HighlightsIdentification of the relevant studies in tracking for mobile devices.Classification schema of the field.Systematic map of the existing research in the area.Discussion about the major findings of this study.Web application with a catalog of classified studies that is collaboratively updated.

Voxar Puzzle: An Innovative Hardware/Software Computer Vision Game for Children Development

This paper exposes how we united computervision technology and tangible user interfaces to conceive aninnovative product targeting children audience. Voxar Puzzle isa digital game in which children have to choose a puzzle froma virtual library and assemble it by manipulating physicalblocks. Furthermore, the process used for the development ofthe game platform had innovation in mind. A Blue Oceanstrategy was used to define the functionalities and features ofthe game platform, comparing it with relevant competitors.The final result was a prototype with a professional interfacethat was validated with children from a local public school.

Incremental structural modeling on sparse visual SLAM

This paper presents an incremental structural modeling approach that improves the precision and stability of existing batch based methods for sparse and noisy point clouds from visual SLAM. The main idea is to use the generating process of point clouds on SLAM effectively. First, a batch based method is applied to point clouds that are incrementally generated from SLAM. Then, the temporal history of reconstructed geometric primitives is statistically merged to suppress incorrect reconstruction. The evaluation shows that both precision and stability are improved compared to a batch based method and the proposed method is suitable for real-time structural modeling.

Authoring Tools for Augmented Reality: An Analysis and Classification of Content Design Tools

Augmented Reality Authoring Tools are important instruments that can help a widespread use of Augmented Reality. They can be classified as programming or content design tools in which the latter completely removes the necessity of programming skills to develop an Augmented Reality solution. Several solutions have been developed in the past years, however there are few works aiming to identify patterns and general models for such tools. This work aims to perform a trend analysis on content design tools in order to identify their functionalities regarding Augmented Reality, authoring paradigms, deployment strategies and general dataflow models. This work is aimed to assist developers willing to create authoring tools, therefore, it focuses on the last three aspects. Thus, 24 tools were analyzed and through this evaluation it were identified two authoring paradigms and two deployment strategies. Moreover, from their combination it was possible to elaborate four generic dataflow models in which every tool could be fit into.