Consistently Orienting Facets in Polygon Meshes by Minimizing the Dirichlet Energy of Generalized Winding Numbers

Jacobson et al. [JKSH13] hypothesized that the local coherency of the generalized winding number function could be used to correctly determine consistent facet orientations in polygon meshes. We report on an approach to consistently orienting facets in polygon meshes by minimizing the Dirichlet energy of generalized winding numbers. While the energy can be concisely formulated and efficiently computed, we found that this approach is fundamentally flawed and is unfortunately not applicable for most handmade meshes shared on popular mesh repositories such as Google 3D Warehouse.Comment: 6 pages, 4 figure

A Simple Method for Correcting Facet Orientations in Polygon Meshes Based on Ray Casting

We present a method for fixing incorrect orientations of facets in an input polygon mesh, a problem often seen in popular 3D model repositories, such that the front side of facets is visible from viewpoints outside of a solid shape represented or implied by the mesh. As opposed to previously proposed methods which are rather complex and hard to reproduce, our method is very simple, only requiring sampling visibilities by shooting many rays. We also propose a simple heuristic to handle interior facets that are invisible from exterior viewpoints. Our method is evaluated extensively with the SHREC’10 Generic 3D Warehouse dataset containing 3168 manually designed meshes, and is demonstrated to be very effective

Vignette: A Style Preserving Sketching Tool for Pen-and-Ink Illustration with Texture Synthesis

Pen-and-ink illustrations take significant amounts of skill, artistry, and patience to create. Digital tools are widely used to accelerate the process; but they provide less artistic freedom and cannot easily capture illustrators ’ personal style. Furthermore, these tool

Volumetric modeling with diffusion surfaces

The modeling of volumetric objects is still a difficult problem. Solid texture synthesis methods enable the design of volumes with homogeneous textures, but global features such as smoothly varying colors seen in vegetables and fruits are difficult to model. In this paper, we propose a representation called diffusion surfaces (DSs) to enable modeling such objects. DSs consist of 3D surfaces with colors defined on both sides, such that the interior colors in the volume are obtained by diffusing colors from nearby surfaces. A straightforward way to compute color diffusion is to solve a volumetric Poisson equation with the colors of the DSs as boundary conditions, but it requires expensive volumetric meshing which is not appropriate for interactive modeling. We therefore propose to interpolate colors only locally at user-defined cross-sections using a modified version of the positive mean value coordinates algorithm to avoid volumetric meshing. DSs are generally applicable to model many different kinds of objects with internal structures. As a case study, we present a simple sketch-based interface for modeling objects with rotational symmetries that can also generate random variations of models. We demonstrate the effectiveness of our approach through various DSs models with simple non-photorealistic rendering techniques enabled by DSs. CR Categories: I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism—Color, shading, shadowing, and textur