A New Contour Reconstruction Approach from Dexel Data in Virtual Sculpting

This paper presents a novel method of contour reconstruction from dexel data solving the shape anomalies for the complex geometry in virtual sculpting. Grouping and traversing processes are developed to find connectivity between dexels along every two adjacent rays. After traveling through all the rays on one slice, sub-boundaries are connected into full boundaries which are desired contours. The complexity of the new method has been investigated and determined as O(n). We also demonstrate the ability of the described method for viewing a sculpted model from different directions

Application of the level set method for the visual representation of continuous cellular automata oriented to anisotropic wet etching

[EN] Atomistic models are a very valuable simulation tool in the field of material science. Among them are the continuous cellular automata (CCA), which can simulate accurately the process of chemical etching used in micro-electro-mechanical-systems (MEMS) micromachining. Due to the CCA intrinsic atomistic nature, simulation results are obtained in the form of a cloud of points, so data visualization has been usually problematic. When using these models as a part of a computer aided design tool, good data visualization is very important. In this paper, a minimum energy model implemented with the level set (LS) method for improving the visual representation of simulated MEMS is presented. Additionally, the sparse field method has been applied to reduce the high computational cost of the original LS. Finally, some reconstructed surfaces with completely different topologies are presented, proving the effectiveness of our implementation and the fact that it is capable of producing any real surface, flat and smooth ones.We thank Miguel Angel Gosalvez for his collaboration in the early stages of this research. This work has been supported by the Spanish FPI-MICINN BES-2011-045940 grant. Also, we acknowledge support by the JAE-Doc grant form the Junta para la Ampliacion de Estudios program co-funded by FSE.Montoliu Álvaro, C.; Ferrando Jódar, N.; Cerdá Boluda, J.; Colom Palero, RJ. (2014). Application of the level set method for the visual representation of continuous cellular automata oriented to anisotropic wet etching. International Journal of Computer Mathematics. 91(1):124-134. https://doi.org/10.1080/00207160.2013.801464S12413491

LIPIcs

Given a finite set A ⊂ ℝ^d, let Cov_{r,k} denote the set of all points within distance r to at least k points of A. Allowing r and k to vary, we obtain a 2-parameter family of spaces that grow larger when r increases or k decreases, called the multicover bifiltration. Motivated by the problem of computing the homology of this bifiltration, we introduce two closely related combinatorial bifiltrations, one polyhedral and the other simplicial, which are both topologically equivalent to the multicover bifiltration and far smaller than a Čech-based model considered in prior work of Sheehy. Our polyhedral construction is a bifiltration of the rhomboid tiling of Edelsbrunner and Osang, and can be efficiently computed using a variant of an algorithm given by these authors as well. Using an implementation for dimension 2 and 3, we provide experimental results. Our simplicial construction is useful for understanding the polyhedral construction and proving its correctness

Computing the Multicover Bifiltration

Given a finite set $A\subset\mathbb{R}^d$, let Cov$_{r,k}$ denote the set of all points within distance $r$ to at least $k$ points of $A$. Allowing $r$ and $k$ to vary, we obtain a 2-parameter family of spaces that grow larger when $r$ increases or $k$ decreases, called the \emph{multicover bifiltration}. Motivated by the problem of computing the homology of this bifiltration, we introduce two closely related combinatorial bifiltrations, one polyhedral and the other simplicial, which are both topologically equivalent to the multicover bifiltration and far smaller than a \v Cech-based model considered in prior work of Sheehy. Our polyhedral construction is a bifiltration of the rhomboid tiling of Edelsbrunner and Osang, and can be efficiently computed using a variant of an algorithm given by these authors. Using an implementation for dimension 2 and 3, we provide experimental results. Our simplicial construction is useful for understanding the polyhedral construction and proving its correctness.Comment: 25 pages, 8 figures, 4 tables. Extended version of a paper accepted to the 2021 Symposium on Computational Geometr

Point Cloud Data Cleaning and Refining for 3D As-Built Modeling of Built Infrastructure

Spatial sensing of built infrastructure is now a common practice within the AEC industry and results are commonly encapsulated in the form of dense point cloud data (PCD). PCD of built infrastructure might consist of millions of spatial points and it is well known that processing all these points is neither necessary nor computationally feasible. In addition, due to several reasons including hardware and/or software deficiencies, there might be several outliers that need to be removed from the PCD before further processing. As the result, cleaning and refining PCD is a paramount step in the process of spatial sensing and object-oriented modeling of built infrastructure scenes. This research work entails two parts: The first part provides an in-depth literature review on current states of practice and research on the concept of PCD cleaning. The second part presents the authors’ suggested framework for cleaning and refining PCD of built infrastructure. This prototype mainly consists of three major components: (1) removing outliers; (2) filling holes and gaps on surfaces of PCD; and (3) balancing the density of different areas of PCD based on a plane recognition approach. Several case studies are presented to demonstrate the efficiency of the proposed framework.This is the author accepted manuscript. The final version is available from ASCE via https://doi.org/10.1061/9780784479827.093#sthash.SfsxrNpd.dpu

Data Product Specification Proposal for Architectural Heritage Documentation with Photogrammetric Techniques: A Case Study in Brazil

peer reviewedPhotogrammetric documentation can provide a sound database for the needs of architectural heritage preservation. However, the major part of photogrammetric documentation production is not used for subsequent architectural heritage projects, due to lack of knowledge of photogrammetric documentation accuracy. In addition, there are only a few studies with rigorous analysis of the requirements for photogrammetric documentation of architectural heritage. In particular, requirements focusing on the geometry of the models generated by fully digital photogrammetric processes are missing. Considering these needs, this paper presents a procedure for architectural heritage documentation with photogrammetric techniques based on a previous review of existing standards of architectural heritage documentation. The data product specification proposed was elaborated conforming to ISO 19131 recommendations. We present the procedure with two case studies in the context of Brazilian architectural heritage documentation. Quality analysis of the produced models were performed considering ISO 19157 elements, such as positional accuracy, logical consistency and completeness, meeting the requirements. Our results confirm that the proposed requirements for photogrammetric documentation are viable

Using the deformable simplicial complex to reconstruct surfaces from point clouds

We present in this thesis a modification to the deformable simplicial complex method that allows it to reconstruct surfaces given only a point cloud extracted from a Wavefront .obj file. By creating a velocity function that moves the vertices of an existing tetrahedral mesh towards their respective closest points in the cloud, we create a final surface that bears the likeness of the cloud itself, while not requiring any information as to the original mesh. The reconstructed surface is resistant to fracturing and webbing, and is able to connect nearby vertices while keeping a clear mesh interface boundary, which prevents the intersection of faces from occurring. We demonstrate our implementation with several examples derived from common .obj files and discuss the strengths and weaknesses of our approach with respect to each