Robust interactive cutting based on an adaptive octree simulation mesh

We present an adaptive octree based approach for interactive cutting of deformable objects. Our technique relies on efficient refine- and node split-operations. These are sufficient to robustly represent cuts in the mechanical simulation mesh. A high-resolution surface embedded into the octree is employed to represent a cut visually. Model modification is performed in the rest state of the object, which is accomplished by back-transformation of the blade geometry. This results in an improved robustness of our approach. Further, an efficient update of the correspondences between simulation elements and surface vertices is proposed. The robustness and efficiency of our approach is underlined in test examples as well as by integrating it into a prototype surgical simulato

Incorporación de fuerzas de presión al modelado de cuerpos blandos

Se presenta un sistema de manejo de objetos flexibles 3D basado en leyes físicas, con fin de realizar diversas técnicas de modelado interactivo, a partir de una interfaz 2D. Se utiliza como motor un sistema de Mass-Spring-Damper extendido, con la incorporación de una fuerza interna adicional para representar el comportamiento de objetos de materiales blandos; el modelado puede desenvolverse ya sea aplicando fuerzas externas como controlando la interna, este método es lo suficientemente simple para dar buenos resultados en tiempos interactivosIII Workshop de Computación Gráfica, Imágenes y Visualización (WCGIV)Red de Universidades con Carreras en Informática (RedUNCI

Incorporación de fuerzas de presión al modelado de cuerpos blandos

Se presenta un sistema de manejo de objetos flexibles 3D basado en leyes físicas, con fin de realizar diversas técnicas de modelado interactivo, a partir de una interfaz 2D. Se utiliza como motor un sistema de Mass-Spring-Damper extendido, con la incorporación de una fuerza interna adicional para representar el comportamiento de objetos de materiales blandos; el modelado puede desenvolverse ya sea aplicando fuerzas externas como controlando la interna, este método es lo suficientemente simple para dar buenos resultados en tiempos interactivosIII Workshop de Computación Gráfica, Imágenes y Visualización (WCGIV)Red de Universidades con Carreras en Informática (RedUNCI

Master of Science

thesisWe present a procedure for generating a coarse, high-quality, tetrahedral mesh whose exterior surface encloses and approximates a given triangle mesh. A tetrahedral mesh is useful for computing perturbation of the triangle mesh based on continuum mechanics: perturbation such as plastic flow, fracture, and elastic deformation. The computer graphics community has long used this physics-based simulation to produce animations of objects exhibiting such physical phenomena. Interactive animation applications such as industrial design, medical training, and computer entertainment require meshes that are particularly efficient and robust, and our meshing procedure targets these properties. We begin with a BCC background lattice and sculpt an initial mesh from it whose tetrahedra occupy some of the volume bounded by the triangle mesh. We then refine this initial mesh with an iterative optimization procedure that simultaneously minimizes the distance from the triangle mesh to the surface of the tetrahedral mesh and maximizes the numerical quality of the tetrahedra. Our procedure provides a trade-off among the mesh's quality, resolution, and degree of approximation of the triangle mesh

Footwear bio-modelling: An industrial approach

There is a growing need within the footwear sector to customise the design of the last from which a specific footwear style is to be produced. This customisation is necessary for user comfort and health reasons, as the user needs to wear a suitable shoe. For this purpose, a relationship must be established between the user foot and the last with which the style will be made; up until now, no model has existed that integrates both elements. On the one hand, traditional customised footwear manufacturing techniques are based on purely artisanal procedures which make the process arduous and complex; on the other hand, geometric models proposed by different authors present the impossibility of implementing them in an industrial environment with limited resources for the acquisition of morphometric and structural data for the foot, apart from the fact that they do not prove to be sufficiently accurate given the non-similarity of the foot and last. In this paper, two interrelated geometric models are defined, the first, a bio-deformable foot model and the second, a deformable last model. The experiments completed show the goodness of the model, with it obtaining satisfactory results in terms of comfort, efficiency and precision, which make it viable for use in the sector

Resolution independent curved seams in clothing animation using a regular particle grid

We present a method for representing seams in clothing animation, and its application in simulation level of detail. Specifically we consider cloth represented as a regular grid of particles connected by spring-dampers, and a seam specified by a closed set of parametric trim curves in the cloth domain. Conventional cloth animation requires the tessellation of seams so that they are handled uniformly by the dynamics process. Our goal is a seam definition which does not constrain the attached clothing panels to be of the same resolution, or even constant resolution, while not being a hindrance to the dynamics process. We also apply our seams to cloth defined on a regular grid, as opposed to the irregular meshes commonly used with seams. The determination of particles interior to the cloth panel can be done using wellknown graphics operations such as scan-conversion. Due to the particle-based nature of the simulation, the dynamics approach combines easily with existing implicit and explicit methods. Finally, because the seams are resolution independent, the particle density per clothing panel can be adjusted as desired. This gives rise to a simple application of the given seams approach illustrating how it may be used for simulation level of detail

An adaptive variational finite difference framework for efficient symmetric octree viscosity

While pressure forces are often the bottleneck in (near-)inviscid fluid simulations, viscosity can impose orders of magnitude greater computational costs at lower Reynolds numbers. We propose an implicit octree finite difference discretization that significantly accelerates the solution of the free surface viscosity equations using adaptive staggered grids, while supporting viscous buckling and rotation effects, variable viscosity, and interaction with scripted moving solids. In experimental comparisons against regular grids, our method reduced the number of active velocity degrees of freedom by as much as a factor of 7.7 and reduced linear system solution times by factors between 3.8 and 9.4. We achieve this by developing a novel adaptive variational finite difference methodology for octrees and applying it to the optimization form of the viscosity problem. This yields a linear system that is symmetric positive definite by construction, unlike naive finite difference/volume methods, and much sparser than a hypothetical finite element alternative. Grid refinement studies show spatial convergence at first order in L∞ and second order in L1, while the significantly smaller size of the octree linear systems allows for the solution of viscous forces at higher effective resolutions than with regular grids. We demonstrate the practical benefits of our adaptive scheme by replacing the regular grid viscosity step of a commercial liquid simulator (Houdini) to yield large speed-ups, and by incorporating it into an existing inviscid octree simulator to add support for viscous flows. Animations of viscous liquids pouring, bending, stirring, buckling, and melting illustrate that our octree method offers significant computational gains and excellent visual consistency with its regular grid counterpart.This work was supported in part by the Natural Sciences and Engineering Research Council of Canada (RGPIN-04360-2014, CRDPJ-499952-2016) and the Rutgers University start-up grant