New metric products, movies and 3D models from old stereopairs and their application to the in situ palaeontological site of Ambrona

[ES] Este artículo está basado en la información del siguiente proyecto:● LDGP_mem_006-1: "[S_Ambrona_Insitu] Levantamiento fotogramétrico del yacimiento paleontológico “Museo in situ” de Ambrona (Soria)", http://hdl.handle.net/10810/7353● LDGP_mem_006-1: "[S_Ambrona_Insitu] Levantamiento fotogramétrico del yacimiento paleontológico “Museo in situ” de Ambrona (Soria)", http://hdl.handle.net/10810/7353[EN] This paper is based on the information gathered in the following project:[EN] 3D modelling tools from photographic pictures have experienced significant improvements in the last years. One of the most outstanding changes is the spread of the photogrammetric systems based on algorithms referred to as Structure from Motion (SfM) in contrast with the traditional stereoscopic pairs. Nevertheless, the availability of important collections of stereoscopic registers collected during past decades invites us to explore the possibilities for re-using these photographs in order to generate new multimedia products, especially due to the fact that many of the documented elements have been largely altered or even disappeared. This article analyses an example of application to the re-use of a collection of photographs from the palaeontological site of Ambrona (Soria, Spain). More specifically, different pieces of software based on Structure from Motion (SfM) algorithms for the generation of 3D models with photographic textures are tested and some derived products such as orthoimages, video or applications of Augmented Reality (AR) are presented.[ES] Las herramientas de modelado 3D a partir de imágenes fotográficas han experimentado avances muy significativos en los últimos años. Uno de los más destacados corresponde a la generalización de los sistemas fotogramétricos basados en los algoritmos denominados Structure from Motion (SfM) sobre los proyectos de documentación tradicional basados en pares estereoscópicos. La existencia de importantes colecciones de registros estereoscópicos realizados durante las décadas anteriores invita a explorar las posibilidades de reutilización de estos registros para la obtención de productos multimedia actuales, máxime cuando algunos de los elementos documentados han sufrido grandes modificaciones o incluso desaparecido. En el presente artículo se analiza la reutilización de colecciones fotográficas de yacimientos paleontológicos mediante un ejemplo centrado en el yacimiento de Ambrona (Soria, España). En concreto, se contrastan varios programas basados en los algoritmos denominados Structure from Motion (SfM) para la generación del modelo 3D con textura y otros productos derivados como ortoimágenes, vídeos o aplicaciones de Realidad Aumentada (RA)

A video object generation tool allowing friendly user interaction

In this paper we describe an interactive video object segmentation tool developed in the framework of the ACTS-AC098 MOMUSYS project. The Video Object Generator with User Environment (VOGUE) combines three different sets of automatic and semi-automatic-tool (spatial segmentation, object tracking and temporal segmentation) with general purpose tools for user interaction. The result is an integrated environment allowing the user-assisted segmentation of any sort of video sequences in a friendly and efficient manner.Peer ReviewedPostprint (published version

Texture dependence of motion sensing and free flight behavior in blowflies

Lindemann JP, Egelhaaf M. Texture dependence of motion sensing and free flight behavior in blowflies. Frontiers in Behavioral Neuroscience. 2013;6:92.Many flying insects exhibit an active flight and gaze strategy: purely translational flight segments alternate with quick turns called saccades. To generate such a saccadic flight pattern, the animals decide the timing, direction, and amplitude of the next saccade during the previous translatory intersaccadic interval. The information underlying these decisions is assumed to be extracted from the retinal image displacements (optic flow), which scale with the distance to objects during the intersaccadic flight phases. In an earlier study we proposed a saccade-generation mechanism based on the responses of large-field motion-sensitive neurons. In closed-loop simulations we achieved collision avoidance behavior in a limited set of environments but observed collisions in others. Here we show by open-loop simulations that the cause of this observation is the known texture-dependence of elementary motion detection in flies, reflected also in the responses of large-field neurons as used in our model. We verified by electrophysiological experiments that this result is not an artifact of the sensory model. Already subtle changes in the texture may lead to qualitative differences in the responses of both our model cells and their biological counterparts in the fly's brain. Nonetheless, free flight behavior of blowflies is only moderately affected by such texture changes. This divergent texture dependence of motion-sensitive neurons and behavioral performance suggests either mechanisms that compensate for the texture dependence of the visual motion pathway at the level of the circuits generating the saccadic turn decisions or the involvement of a hypothetical parallel pathway in saccadic control that provides the information for collision avoidance independent of the textural properties of the environment

Stereo and motion parallax cues in human 3D vision: can they vanish without a trace?

In an immersive virtual reality environment, subjects fail to notice when a scene expands or contracts around them, despite correct and consistent information from binocular stereopsis and motion parallax, resulting in gross failures of size constancy (A. Glennerster, L. Tcheang, S. J. Gilson, A. W. Fitzgibbon, & A. J. Parker, 2006). We determined whether the integration of stereopsis/motion parallax cues with texture-based cues could be modified through feedback. Subjects compared the size of two objects, each visible when the room was of a different size. As the subject walked, the room expanded or contracted, although subjects failed to notice any change. Subjects were given feedback about the accuracy of their size judgments, where the “correct” size setting was defined either by texture-based cues or (in a separate experiment) by stereo/motion parallax cues. Because of feedback, observers were able to adjust responses such that fewer errors were made. For texture-based feedback, the pattern of responses was consistent with observers weighting texture cues more heavily. However, for stereo/motion parallax feedback, performance in many conditions became worse such that, paradoxically, biases moved away from the point reinforced by the feedback. This can be explained by assuming that subjects remap the relationship between stereo/motion parallax cues and perceived size or that they develop strategies to change their criterion for a size match on different trials. In either case, subjects appear not to have direct access to stereo/motion parallax cues

A segmentation-based coding system allowing manipulation of objects (sesame)

We present a coding scheme that achieves, for each image in the sequence, the best segmentation in terms of rate-distortion theory. It is obtained from a set of initial regions and a set of available coding techniques. The segmentation combines spatial and motion criteria. It selects at each area of the image the most adequate criterion for defining a partition in order to obtain the best compromise between cost and quality. In addition, the proposed scheme is very suitable for addressing content-based functionalities.Peer ReviewedPostprint (published version

3D face tracking and multi-scale, spatio-temporal analysis of linguistically significant facial expressions and head positions in ASL

Essential grammatical information is conveyed in signed languages by clusters of events involving facial expressions and movements of the head and upper body. This poses a significant challenge for computer-based sign language recognition. Here, we present new methods for the recognition of nonmanual grammatical markers in American Sign Language (ASL) based on: (1) new 3D tracking methods for the estimation of 3D head pose and facial expressions to determine the relevant low-level features; (2) methods for higher-level analysis of component events (raised/lowered eyebrows, periodic head nods and head shakes) used in grammatical markings—with differentiation of temporal phases (onset, core, offset, where appropriate), analysis of their characteristic properties, and extraction of corresponding features; (3) a 2-level learning framework to combine lowand high-level features of differing spatio-temporal scales. This new approach achieves significantly better tracking and recognition results than our previous methods

On using gait to enhance frontal face extraction

Visual surveillance finds increasing deployment formonitoring urban environments. Operators need to be able to determine identity from surveillance images and often use face recognition for this purpose. In surveillance environments, it is necessary to handle pose variation of the human head, low frame rate, and low resolution input images. We describe the first use of gait to enable face acquisition and recognition, by analysis of 3-D head motion and gait trajectory, with super-resolution analysis. We use region- and distance-based refinement of head pose estimation. We develop a direct mapping to relate the 2-D image with a 3-D model. In gait trajectory analysis, we model the looming effect so as to obtain the correct face region. Based on head position and the gait trajectory, we can reconstruct high-quality frontal face images which are demonstrated to be suitable for face recognition. The contributions of this research include the construction of a 3-D model for pose estimation from planar imagery and the first use of gait information to enhance the face extraction process allowing for deployment in surveillance scenario