Temporally Coherent Sculpture of Composite Objects

Special Issue of Shape Modeling International (SMI 2016)International audienceWe address the problem of virtual sculpting and deformation of shapes composed of small, randomly placed objects. Objects may be tightly packed-such as pebbles, pills, seeds and grains, or be sparsely distributed with an overarching shape-such as flocks of birds or schools of fish. Virtual sculpture has rapidly become a standard in the entertainment industry. Composites, though, are still usually created in a static way by individually placing each object or by sculpting a support surface and procedurally populating the final shape. That raises problems for the generalisation to evolving shapes with visual continuity of the components. Large amounts of geometrical data are generated, and must be maintained and processed, both by the CPU and by the GPU. Whenever the shape is deformed, one has to define how these compositing objects should turn, displace or disappear inside the volume, as well as how new instances should become visible to the outside. It is difficult to rely on a physical system to perform that task in real time. The system we suggest can be constructed upon any uniform mesh-based representation that can be deformed and whose connectivity can be updated by operations such as edge splits, collapses, and flips. The mesh remains populated with an aperiodic distribution of composing elements that are automatically updated under deformation. The idea is to sculpt the shape as if it were filled with little objects, without handling the complexity of manipulating volumetric shapes. For this purpose, we suggest exploiting the properties of the uniform sampling of the surface. We show that we are able to properly handle virtual sculpting of composites in real-time and maintaining temporal continuity. This system also uses GPU optimisations to render individual elements efficiently. To our knowledge, no previous sculpting system allows the user to simultaneously see and sculpt agglomerates in such a fast and reliable fashion

An Algorithm for Two-Dimensional Mesh Generation for Arbitrary Regions with Cracks

This paper describes an algorithm for generating unstructured triangulations for arbitrarily shaped twodimensional regions. The algorithm works for regions without cracks, as well as for regions with one or multiple cracks. The algorithm incorporates aspects of well-known meshing procedures and includes some original steps. I

A STRATEGY FOR IMPROVING THE ROBUSTNESS OF THREE-DIMENSIONAL ADVANCING-FRONT ALGORITHMS

Abstract. This work presents a back-tracking strategy for improving the robustness of advancing-front algorithms for mesh generation in three-dimensional models. It can be observed, in many advancing-front based algorithms for three dimensions, that a number of regions that can not be meshed is left after the mesh generation process, which stops the algorithms from converging. These regions are represented by polyhedra and are formed by elements of the current front, which are faces in three dimensions. These regions are usually disconnected, since they are defined by adjacent elements that form a closed loop, and they can not be meshed, even with the insertion of additional new nodes. A backtracking procedure is applied to all of these regions, in order to guarantee robustness in mesh generation. It is devised for three-dimensional cases, because this problem has no counterpart in two dimensions. Examples of generated meshes using the back-tracking procedure are presented in order to validate the strategy proposed in this work. Keywords: Three-dimensional Mesh Generation, Advancing-Front, Back-tracking 1