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Abstract: Subdividing surfaces into cylinders is a significant question in various applications. Even if specific approaches have been described in several domains, most of the time topological properties are not explicitly handled, and the segmentation remains mainly driven by geometry. We present here an original approach to describe the topological and combinatorial nature of a tiling with cylinders. We first introduce m-cellular complexes, a framework allowing the flexible description of cuttings and tilings. Then we describe n-loops, an extension of the loops for producing tilings with cylinders. Computational issues of n-loops are then addressed, using both topological and geometrical properties of the surface. Finally, we propose two applications, first tiling a surface with large quadrangles patches, and then segmenting surfaces with possible protrusions. [Copyright &y& Elsevier]

Tactile maps are essential tools for visually impaired people to comprehend space and to support the simple pedestrian trips made difficult by their disability. Tactile maps are created manually and printed by specialists, and it takes a large amount of time to create a new one, which prevents using them on demand for everyday use. As a consequence, researchers and cartographers try to automate this creation process, but the existing automated derivation processes do not include generalization or advanced stylization steps, which limits their effectiveness. This paper reports first experiments to include such complex automated cartography processes to provide on-demand tactile maps for visually impaired people. These first experiments were more intended to raise real research issues than solve them, and the paper discusses these issues in a research agenda to achieve automatically derived tactile maps. [ABSTRACT FROM AUTHOR]

The main purpose of this work is to determine the exact maximum number of pixels (a bi-dimensional sequence of unit squares tiling a plane) that a rectifiable curve of given length l can cross. In other words, given l ∈ R , we provide the value N ( l ) of the maximal cardinality of the digital cover of a rectifiable curve of length l . The optimal curves are polygonal curves with integer vertices, 0, 1 or 2 vertical or horizontal steps and an arbitrary number of diagonal steps. We also report the properties of the staircase function N ( l ) , which is affinely periodic in the sense that N ( l + 2 ) = N ( l ) + 3 and a bound N ( l ) ≤ 4 + 3 2 l . Our second aim is to look at the restricted class of closed curves and offer some conjectures on the maximum number N closed ( l ) of pixels that a closed curve of length l can cross. This work finds its application in the quadtree complexity theorem. This well-known result bounds the number of quads with a shape of perimeter p by 16 q − 11 + 16 p . However, this linear bound is not tight. From our new upper bound N closed ( l ) ≤ N ( l ) ≤ 4 + 3 2 l we derive a new improved multiresolution complexity theorem: Number(quads) ≤ 16 q − 11 + 6 2 p . Lastly, we show that this new bound is tight up to a maximal error of 16 ( q − 1 ) . [ABSTRACT FROM AUTHOR]

Terrestrial Laser Scanning (TLS) systems have gained increasing popularity in the forestry domain and are today widely used for the automatic measurement of forest inventory attributes. Nevertheless, to the best of our knowledge the problem of tree species recognition from TLS data has received very little attention from the scientific community. It is in this context that we present a novel Computer-Aided Tree Species Identification method based on 3D bark texture analysis. The novelty of our approach resides in the following three key points: (1) 3D salient regions extraction using a new morphological segmentation method that we have called Burst Wind Segmentation, (2) the extraction and pre-annotation of a collection of typical 3D bark patterns, known as scars, from each of the tree species. The pre-annotated scars are stored in a dictionary that we have called ScarBook and they are used as a reference for the comparison of the 3D salient segmented regions, (3) a wide variety of advanced shape, saliency, curvature and roughness features are extracted from the 3D salient segmented regions. To study the performance of our method, an experiment has been carried out on a dataset composed of 969 patches which correspond to 30 cm long segments of the trunk at breast height. Six species among the most dominant species in European forests have been tested with patches of different diameter at breast height values so as to study the identification accuracy with respect to age. The results obtained are very encouraging and promising and they confirm the possibility of identifying tree species using TLS data. [ABSTRACT FROM AUTHOR]

Tactile maps, and even more audio-tactile maps (Brock et al., 2012) are useful tools for visually impaired people to grasp the geographic space that they cannot experience with their sight. Due to low precision of touch compared to sight, these tactile maps have to be very simplified and generalised compared to their counterparts designed for people with regular sight (Touya et al., 2019). This is why it is very complex for orientation and mobility trainers to design and create enough of these maps for their needs. The orientation and mobility trainers we interviewed claim that they need a tool for non-expert GIS users to fasten the time to design and print a new audio-tactile map. Some simple tools exist, such as TouchMapper1, or Hapticke2, which allow the generation of a tactile map anywhere on earth from OpenStreetMap data. But these tools fail to generate maps that are generalised enough (Touya et al., 2019). This is why we started the design of the MULTIMAGE platform (MULtimodal Tactile and Interactive Map GEnerator). The MULTIMAGE platform proposes a workflow with three steps to generate a 3D model ready to be printed from OpenStreetMap data (Figure 1). The first step is just the selection of the extent, the scale, and the size of the map, and then an automated extraction of the corresponding raw data from OpenStreetMap. For now, our focus is on maps of crossroads at large scales, because crossroads are one of the main issues during the training of autonomous mobility for visually impaired people. The extent of the map is simply selected by drawing a bounding box on a web map. Then, the second step of the workflow is the data enrichment, which enables the use of automated enrichment scripts, as well as interactive actions to correct potentially incomplete or incorrect OpenStreetMap data. The third step is the design of the map where stylisation and map generalisation tasks can be carried out, either automatically or interactively. Then, the map is exported as an extended STL file to be 3D-printed, with information to print buttons of audio description. We also plan the platform to be able to export files adapted to swell paper printers, as swell paper (Figure 2) can be used on top of tablets to make interactive audio-tactile devices (Brok et al., 2012). The interactive actions are possible using the map interface presented in Figure 3. As a classical web GIS tool, the edition of the geometry and the semantics of the OSM data will be possible in the second step, and the edition of style as well as manual generalisation operations will be possible in the third step. Regarding the automatic scripts, several are already implemented in the platform. For instance, there is a script to segment and enrich the crossroad with important features such as traffic islands (Favreau & Kalsron, 2022), and a script to generate styles adapted to an audiotactile map (Jiang et al., 2021). The backend, i.e. the server side of the platform is implemented in Python, using open source libraries such as GeoDjango and Geopandas. The web interface is developed in Javascript, based on the OpenLayers library. Data are stored using PostGIS, and the Web Feature Services displayed in the interface are generated with Geoserver. [ABSTRACT FROM AUTHOR]

Abstract: Magnetic resonance (MR) provides a non-invasive way to investigate changes in the brain resulting from aging or neurodegenerative disorders such as Alzheimer''s disease (AD). Performing accurate analysis for population studies is challenging because of the interindividual anatomical variability. A large set of tools is found to perform studies of brain anatomy and population analysis (FreeSurfer, SPM, FSL). In this paper we present a newly developed surface-based processing pipeline (MILXCTE) that allows accurate vertex-wise statistical comparisons of brain modifications, such as cortical thickness (CTE). The brain is first segmented into the three main tissues: white matter, gray matter and cerebrospinal fluid, after CTE is computed, a topology corrected mesh is generated. Partial inflation and non-rigid registration of cortical surfaces to a common space using shape context are then performed. Each of the steps was firstly validated using MR images from the OASIS database. We then applied the pipeline to a sample of individuals randomly selected from the AIBL study on AD and compared with FreeSurfer. For a population of 50 individuals we found correlation of cortical thickness in all the regions of the brain (average r =0.62 left and r =0.64 right hemispheres). We finally computed changes in atrophy in 32 AD patients and 81 healthy elderly individuals. Significant differences were found in regions known to be affected in AD. We demonstrated the validity of the method for use in clinical studies which provides an alternative to well established techniques to compare different imaging biomarkers for the study of neurodegenerative diseases. [Copyright &y& Elsevier]