Interactive Facades Analysis and Synthesis of Semi-Regular Facades

Urban facades regularly contain interesting variations due to allowed deformations of repeated elements (e.g., windows in different open or close positions) posing challenges to state-of-the-art facade analysis algorithms. We propose a semi-automatic framework to recover both repetition patterns of the elements and their individual deformation parameters to produce a factored facade representation. Such a representation enables a range of applications including interactive facade images, improved multi-view stereo reconstruction, facade-level change detection, and novel image editing possibilities

Low-rank Based Algorithms for Rectification, Repetition Detection and De-noising in Urban Images

In this thesis, we aim to solve the problem of automatic image rectification and repeated patterns detection on 2D urban images, using novel low-rank based techniques. Repeated patterns (such as windows, tiles, balconies and doors) are prominent and significant features in urban scenes. Detection of the periodic structures is useful in many applications such as photorealistic 3D reconstruction, 2D-to-3D alignment, facade parsing, city modeling, classification, navigation, visualization in 3D map environments, shape completion, cinematography and 3D games. However both of the image rectification and repeated patterns detection problems are challenging due to scene occlusions, varying illumination, pose variation and sensor noise. Therefore, detection of these repeated patterns becomes very important for city scene analysis. Given a 2D image of urban scene, we automatically rectify a facade image and extract facade textures first. Based on the rectified facade texture, we exploit novel algorithms that extract repeated patterns by using Kronecker product based modeling that is based on a solid theoretical foundation. We have tested our algorithms in a large set of images, which includes building facades from Paris, Hong Kong and New York

Analysis and Manipulation of Repetitive Structures of Varying Shape

Self-similarity and repetitions are ubiquitous in man-made and natural objects. Such structural regularities often relate to form, function, aesthetics, and design considerations. Discovering structural redundancies along with their dominant variations from 3D geometry not only allows us to better understand the underlying objects, but is also beneficial for several geometry processing tasks including compact representation, shape completion, and intuitive shape manipulation. To identify these repetitions, we present a novel detection algorithm based on analyzing a graph of surface features. We combine general feature detection schemes with a RANSAC-based randomized subgraph searching algorithm in order to reliably detect recurring patterns of locally unique structures. A subsequent segmentation step based on a simultaneous region growing is applied to verify that the actual data supports the patterns detected in the feature graphs. We introduce our graph based detection algorithm on the example of rigid repetitive structure detection. Then we extend the approach to allow more general deformations between the detected parts. We introduce subspace symmetries whereby we characterize similarity by requiring the set of repeating structures to form a low dimensional shape space. We discover these structures based on detecting linearly correlated correspondences among graphs of invariant features. The found symmetries along with the modeled variations are useful for a variety of applications including non-local and non-rigid denoising. Employing subspace symmetries for shape editing, we introduce a morphable part model for smart shape manipulation. The input geometry is converted to an assembly of deformable parts with appropriate boundary conditions. Our method uses self-similarities from a single model or corresponding parts of shape collections as training input and allows the user also to reassemble the identified parts in new configurations, thus exploiting both the discrete and continuous learned variations while ensuring appropriate boundary conditions across part boundaries. We obtain an interactive yet intuitive shape deformation framework producing realistic deformations on classes of objects that are difficult to edit using repetition-unaware deformation techniques

A Survey of Surface Reconstruction from Point Clouds

International audienceThe area of surface reconstruction has seen substantial progress in the past two decades. The traditional problem addressed by surface reconstruction is to recover the digital representation of a physical shape that has been scanned, where the scanned data contains a wide variety of defects. While much of the earlier work has been focused on reconstructing a piece-wise smooth representation of the original shape, recent work has taken on more specialized priors to address significantly challenging data imperfections, where the reconstruction can take on different representations – not necessarily the explicit geometry. We survey the field of surface reconstruction, and provide a categorization with respect to priors, data imperfections, and reconstruction output. By considering a holistic view of surface reconstruction, we show a detailed characterization of the field, highlight similarities between diverse reconstruction techniques, and provide directions for future work in surface reconstruction

Open/closed window research: sound insulation through ventilated domestic windows.

Planning guidance is required to advise on appropriate standards against which the suitability of development can be assessed. Consideration is needed of the locale, itsexisting character and of future residential amenity. In the noise context, advice is primarily required to define threshold exposure levels relative to extraneous sources of environmental noise. A thorough knowledge of the acoustic transmission characteristics afforded by the building envelope is therefore desirable to assist in the setting of threshold levels and to aid in the design and verification of developmentproposals.The insulation of an open window has been generally accepted as being 10-15 dBA although its precision and affect on opening style, open area and window size, arenot readily available. A programme of laboratory measurements have been undertaken by the Building Performance Centre at Napier University on behalf of theDepartment for Environment, Food and Rural Affairs, in order to quantify the sound insulation provided by a variety of window types, opening styles, areas of openingand ventilator devices.Open Windows: The test regime measured the sound insulation provided by seven separate windows, with a combination of twelve different opening styles. Thevariation in weighted level difference, Dw, across the different opening styles for approximately equivalent area openings has been consistently measured as between 4 and 6 dB.The range of measured insulation ratings, for window with a free open area of 0.05 m2, is Dw 14 – 20 dB. This translates to the following dBA level differences, due to variations in the source noise characteristics:• Road Traffic Noise 12 –18 dBA• Railway Noise 12 –18 dBA• Aircraft Noise 14 – 19 dBA• Amplified Music 15 –20 dBAThe window results do not show any one opening style which provides significantly better insulating characteristics. In general the set of windows with an outward opening light performed well. The windows with no extending opening lights, namely the internal turn and tilt and the sliding sash, were also among the best performing open units; particularly when the source of noise was neither random nor normal incidence. Variations in the window size, frame material and glazing type have little significance on the insulating performance of an open window.Closed Window. The introduction of a ‘closed’ 4000 mm2 slot ventilator within the window frame reduced the overall weighted insulation performance of the window by 6 dB. This reduction increased to 11 dB when the vent was in its ‘open’ condition.Proprietary over frame vents gave a marked improvement in the high frequency acoustic performance; however the weighted insulation rating is generally dominated by low-frequency transmission which is not substantially improved over that of a slot vent.Sound Directivity: Rotation of source incidence away from the normal, within a nondiffuse acoustic environment, is found to consistently improve the resulting open window façade insulation