Publication date: February 2017 Source:Computers & Graphics, Volume 62 Author(s): Ojaswa Sharma, Nidhi Agarwal In this paper, we propose an algorithm for closed and smooth 3D surface reconstruction from unorganized planar cross-sections. We address the problem in its full generality, and show its effectiveness on sparse sets of cutting planes. Our algorithm is based on the construction of a globally consistent signed distance function over the cutting planes. It uses a split-and-merge approach utilising Hermite mean-value interpolation for triangular meshes. This work improves on recent approaches by providing a simplified construction that avoids need for post-processing to smooth the reconstructed object boundary. We provide results of reconstruction and its comparison with other algorithms. We build on our recent work by providing a better estimate of normals along the cross-sectional curves, and by showing robustness of the algorithm under increasing number of cutting planes.
Publication date: Available online 2 June 2017 Source:Computers & Graphics Author(s): Zhonggui Chen, Zifu Shen, Jianzhi Guo, Juan Cao, Xiaoming Zeng This paper focuses on the problem of generating a line drawing from a given image for fused deposition modeling. The abstracted line drawing, comprising of lines with a single color and thickness, would preserve both tone and edges of the input image. We first partition the image into sub-regions manually. The boundaries of the sub-regions are extracted as the feature lines of the image. Next, a proper number of points are randomly placed on the image plane with a density proportional to the darkness of the image. We use Lloyd’s method to push the sampling points away from each other and the feature lines. The points within each sub-region are then connected by solving a travelling salesman problem (TSP). Finally, we further optimize the fairness and the spacing of the lines by minimizing a tailored objective function. A variety of experimental results are presented to show the effectiveness of our method for generating line drawings for 3D printing.
Publication date: April 2017 Source:Computers & Graphics, Volume 63 Author(s): Abdullah Bulbul, Rozenn Dahyot This paper proposes to use a geotagged virtual world for the visualization of people’s visual interest and their sentiment as captured from their social network activities. Using mobile devices, people widely share their experiences and the things they find interesting through social networks. We experimentally show that accumulating information over a period of time from multiple social network users allows to efficiently map and visualize popular landmarks as found in cities such as Rome in Italy and Dublin in Ireland. The proposed approach is also sensitive to temporal and spatial events that attract visual attention. We visualize the calculated popularity on 3D virtual cities using game engine technologies.
SMI is the premier international forum for the dissemination of new mathematical theories and novel computational techniques for modeling, simulating, and processing digital shape representations. Conference proceedings are published in this special issue of Computers & Graphics
Publication date: Available online 3 June 2017 Source:Computers & Graphics Author(s): Tibor Stanko, Stefanie Hahmann, Georges-Pierre Bonneau, Nathalie Saguin-Sprynski We present a novel framework for acquisition and reconstruction of 3D curves using orientations provided by inertial sensors. While the idea of sensor shape reconstruction is not new, we present the first method for creating well-connected networks with cell complex topology using only orientation and distance measurements and a set of user-defined constraints. By working directly with orientations, our method robustly resolves problems arising from data inconsistency and sensor noise. Although originally designed for reconstruction of physical shapes, the framework can be used for “sketching” new shapes directly in 3D space. We test the performance of the method using two types of acquisition devices: a standard smartphone, and a custom-made device.
Publication date: May 2017 Source:Computers & Graphics, Volume 64 Author(s): Johannes Edelsbrunner, Sven Havemann, Alexei Sourin, Dieter W. Fellner Creation of procedural 3D building models can significantly reduce the costs of modeling, since it allows for generating a variety of similar shapes from one procedural description. The common field of application for procedural modeling is modeling of straight building facades, which are very well suited for shape grammars—a special kind of procedural modeling system. In order to generate round building geometry, we present a way to set up different coordinate systems in shape grammars. Besides Cartesian, these are primarily cylindrical and spherical coordinate systems for generation of structures such as towers or domes, that can procedurally adapt to different dimensions and parameters. The users can apply common splitting idioms from shape grammars in their familiar way for creating round instead of straight geometry. The second enhancement we propose is to provide a way for users to give high level inputs that are used to automatically arrange and adapt parts of the models.
Publication date: Available online 3 June 2017 Source:Computers & Graphics Author(s): Sagi Katz, Ayellet Tal Empty-Region graphs are well-studied in Computer Graphics, Geometric Modeling, Computational Geometry, as well as in Robotics and Computer Vision. The vertices of these graphs are points in space, and two vertices are connected by an arc if there exists an empty region of a certain shape and size between them. In most of the graphs discussed in the literature, the empty region is assumed to be a circle or the union/intersection of circles. In this paper we propose a new type of empty-region graphs—the γ-visibility graph. This graph can accommodate a variety of shapes of empty regions and may be defined in any dimension. Interestingly, we will show that commonly-used shapes are a special case of our graph. In this sense, our graph generalizes some empty-region graphs. Though this paper is mostly theoretical, it may have practical implication—the numerous applications that make use of empty-region graphs would be able to select the best shape that suits the problem at hand.
Publication date: Available online 3 June 2017 Source:Computers & Graphics Author(s): Joris Ravaglia, Alexandra Bac, Richard A. Fourner We propose a novel method for detecting and reconstructing tubular shapes in dense, noisy, occluded and unorganized point clouds. The STEP method (Snakes for Tuboid Extraction from Point clouds) was originally designed to reconstruct woody parts of trees scanned with terrestrial LiDAR in natural forest environments. The STEP method deals with the acquisition artefacts of point clouds from terrestrial LiDAR which include three important constraints: a varying sampling rate, signal occlusion, and the presence of noise. The STEP method uses a combination of an original Hough transform and a new form of growing active contours (also referred to as “snakes”) to overcome these constraints while being able to handle large data sets. The framework proves to be resilient under various conditions as a general shape recognition and reconstruction tool. In the field of forestry, the method was demonstrated to be robust to the previously highlighted limitations (with errors in the range of manual forest measurements, that is 1 cm diameter error). The STEP method has therefore the potential to improve current forest inventories as well as being applied to a wide array of other applications, such as pipeline reconstruction and the assessment of industrial structures.