Comparison of the meccano method with standard mesh generation techniques

[EN]The meccano method is a novel and promising mesh generation technique for simultaneously creating adaptive tetrahedral meshes and volume parameterizations of a complex solid. The method combines several former procedures: a mapping from the meccano boundary to the solid surface, a 3-D local refinement algorithm and a simultaneous mesh untangling and smoothing. In this paper we present the main advantages of our method against other standard mesh generation techniques. We show that our method constructs meshes that can be locally refined by using the Kossaczky bisection rule and maintaining a high mesh quality. Finally, we generate volume T-mesh for isogeometric analysis, based on the volume parameterization obtained by the method…

Mesh Generation for Isogeometric Analysis with T-spline

[EN]The application of the Isogeometric Analysis (IA) with T-splines [1] demands a partition of the parametric space, C, in a tiling containing T-junctions denominated T-mesh. The T-splines are used both for the geometric modelization of the physical domain, D, and the basis of the numerical approximation. They have the advantage over the NURBS of allowing local refinement. In this work we propose a procedure to construct T-spline representations of complex domains in order to be applied to the resolution of elliptic PDE with IA. In precedent works [2, 3] we accomplished this task by using a tetrahedral parametrization…

Mesh Generation and Isogeometric Analysis

[EN]We present advances of the meccano method [1,2] for tetrahedral mesh generation and volumetric parameterization of solids. The method combines several former procedures: a mapping from the meccano boundary to the solid surface, a 3-D local refinement algorithm and a simultaneous mesh untangling and smoothing. The key of the method lies in defining a one-to-one volumetric transformation between the parametric and physical domains. Results with adaptive finite elements will be shown for several engineering problems. In addition, the application of the method to T-spline modelling and isogeometric analysis [3,4] of complex geometries will be introduced…

T-spline parameterization of 2D geometries based on the meccano method with a new T-mesh optimization algorithm

[EN]We present a new method, based on the idea of the meccano method and a novel T-mesh optimization procedure, to construct a T-spline parameterization of 2D geometries for the application of isogeometric analysis. The proposed method only demands a boundary representation of the geometry as input data. The algorithm obtains, as a result, high quality parametric transformation between 2D objects and the parametric domain, the unit square. First, we define a parametric mapping between the input boundary of the object and the boundary of the parametric domain. Then, we build a T-mesh adapted to the geometric singularities of the domain in order to preserve the features of the object boundary with a desired tolerance…

Tetrahedral mesh optimization combining boundary and inner node relocation and adaptive local refinement

[EN]This work introduces a new technique for tetrahedral mesh optimization. The procedure relocates boundary and inner nodes without changing the mesh topology. In order to maintain the boundary approximation while boundary nodes are moved, a local refinement of tetrahedra with faces on the solid boundary is necessary in some cases. New nodes are projected on the boundary by using a surface parameterization. In this work, the proposed method is applied to tetrahedral meshes of genus-zero solids that are generated by the meccano method. In this case, the solid boundary is automatically decomposed into six surface patches which are parameterized into the six faces of a cube with the Floater parameterization...

Surface insertion in a tetrahedral mesh using the meccano method

[EN]This work presents an innovative method to insert an open surface in a tetrahedral mesh. The insertion of a surface in a mesh can be done with 2 different approaches: introduce the surface to the geometry before generating the mesh, or insert the surface once the mesh is generated. This work uses the second approach. Essentially, the surface is first approximated by a set of faces of the existing mesh. This set is refined to obtain a more accurate approximation. Finally, the set is processed to satisfy some topological properties and projected to the actual surface. The strategy is based on a mesh generated by the Meccano Method…

Un metodo multilivello per la semplificazione di mesh poligonali da scanner 3D

L'algoritmo di semplificazione proposto in questa tesi agisce in modo iterativo su due livelli, in una prima fase alla mesh viene applicato un operatore di smoothing e alla mesh così elaborata viene poi applicata la decimazione. L'alternanza di questi due operatori permette di avere mesh semplificate che mantengono però una qualità maggiore rispetto al risultato che si avrebbe invece applicando solo la decimazione. A partire da una mesh ad alta risoluzione, ad ogni iterazione viene quindi creata una mesh con una risoluzione inferiore fino all'ultima iterazione che produce la mesh coarse (a bassa risoluzione) desiderata. Si viene quindi a creare una struttura di semplificazione multilivello, utile in molte applicazioni di computer graphics.