Catálogo de publicaciones - libros

The Wang Tiles method is a successful and effective technique for the representation of 2D-texture or 3D-geometry. In this paper we present a new method to fill Wang tiles with a 2D-FON distribution or a 3D-geometry in order to achieve a more efficient runtime. We extend the Wang Tiles method to include information about their position. We further demonstrate how the individual tiles are filled with different intensities by using the FON distribution. Additionally, we present several new methods to eliminate errors between the tile edges and the different resource areas applying FON and corners relaxation techniques.

We present a new type of mosaic, the multi-layered stack mosaic with photographs of rotated objects. Our algorithm uses multi-layered Photomosaics with database enrichment by element rotation. The benefit of this algorithm is that an artist can not only produce a digital mosaic with a relatively small database without degrading the quality of the mosaic, but that the Multi-layered Stack Mosaic also generates unique and strong artistic expressions which gives an illusion of piled stackable objects. Since the result has a unique visual style, we intend to exhibit our mosaic images at galleries such as the Epson Color Imaging Contest and the CAU Art Center.

A novel approach for appearance and geometry completion over point-sampled geometry is presented in this paper. Based on the result of surface clustering and the given texture sample, we define a global texture energy function on the point set surface for direct texture synthesis. The color texture completion is performed by minimizing a constrained global energy using the existing texture on the surface as the input texture sample. We convert the issue of context-based geometry completion into a task of texture completion on the surface. The geometric detail is then peeled and converted into a piece of signed gray-scale texture on the base surface of the point set surface. We fill the holes on the base surface by smoothed extrapolation and the geometric details over these patches are reconstructed by a process of gray-scale texture completion. Experiments show that our method is flexible, efficient and easy to implement. It provides a practical texture synthesis and geometry completion tool for 3D point set surfaces.

In this paper we argue for our NPAR system as an effective 2D alternative to most of NPR research which is focused on frame coherent stylised rendering of 3D models. Our approach gives a highly stylised look to images without the support of 3D models, and yet they still behave as though animated by drawing, which they are. First, a stylised brush tool is used to freely draw extreme poses of characters. Each character is built up of 2D drawn brush strokes which are manually grouped into layers. Each layer is assigned its place in a drawing hierarchy called a Hierarchical Display Model (HDM). Next, multiple HDMs are created for the same character, each corresponding to a specific view. A collection of HDMs essentially reintroduces some correspondence information to the 2D drawings needed for in-betweening and, in effect, eliminates the need for a true 3D model. Once the models are composed the animator starts by defining keyframes from extreme poses in time. Next, brush stroke trajectories defined by the keyframe HDMs are in-betweened automatically across intermediate frames. Finally, each HDM of each generated in-between frame is traversed and all elements are drawn one on another from back to front. Our techniques support highly rendered styles which are particularly difficult to animate by traditional means including the ‘airbrushed’, scraperboard, watercolour, Gouache, ‘ink-wash’, and the ‘crayon’ styles. We believe our system offers a new fresh perspective on computer aided animation production and associated tools.

In this paper, we propose a novel mesh deformation approach via manipulating differential properties non-uniformly. Guided by user-specified material properties, our method can deform the surface mesh in a non-uniform way while previous deformation techniques are mainly designed for uniform materials. The non-uniform deformation is achieved by material-dependent gradient field manipulation and Poisson-based reconstruction. Comparing with previous material-oblivious deformation techniques, our method supplies finer control of the deformation process and can generate more realistic results. We propose a novel detail representation that transforms geometric details between successive surface levels as a combination of dihedral angles and barycentric coordinates. This detail representation is similarity-invariant and fully compatible with material properties. Based on these two methods, we implement a multiresolution deformation tool, which allows the user to edit a mesh inside a hierarchy in a material-aware manner. We demonstrate the effectiveness and robustness of our methods by several examples with real-world data.

This paper presents a novel skeleton-based method for deforming meshes, based on an approximate skeleton. The major difference from previous skeleton-based methods is that they used the skeleton to control movement of vertices, whereas we use it to control the simplices defining the model. This allows errors, that occur near joints in other methods, to be spread over the whole mesh, giving smooth transitions near joints. Our method also needs no vertex weights defined on the bones, which can be tedious to choose in previous methods.

To edit or create the animation of a 3D character model has always been an important but time-consuming task, since the animator usually needs to set up the character’s skeleton, paint its binding weights, and adjust its key-poses. Hence, we propose an animation transfer system in this paper to take a well-edited character animation as the input. Then, the system can transfer the skeleton, binding weights, and other attributes of the given character model to another static model with only few corresponding feature points specified. The transferring process is based on a mapping between the space around two character meshes. In this paper, the mapping is called consistent volume parameterization, which inherits consistent surface parameterization. Hence, the animator can start to create a skeleton-driven animation for the new character model without any prior setting. Moreover, our system is also capable of cloning a skeleton-driven animation to several other character models which can be used in a crowd animation.

In this paper, we develop a novel mesh fusion method controlled by sketches, which allows users to construct complex 3D polygon models fast and easily. The user first cuts needed parts from some existing objects and puts them in right pose. Then, a radial basis function (RBF) based implicit surface is adopted to smoothly fuse the parts. To achieve better shape control for the transition part in fusion, our method let users using sketches to specify the expected silhouette. After that, the implicit surface is sampled by particles and meshed into a polygonal surface joining the separated parts into one single model. Compared with other previous methods, our mesh fusion approach overcomes the topological limitations and can merge multiple parts together at once.

In recent years, attention has been paid to particle-based fluid simulation, with several methods being developed to incorporate particle-based simulation into CG animations. These methods reconstruct water surfaces that are usually represented by polygons. However, the computational cost of the surface reconstruction is quite high. Therefore, it is difficult to render the result of the particle-based simulation at interactive frame rates. To address this, we present a real-time method for rendering water surfaces resulting from particle-based simulation. We present an efficient GPU accelerated surface reconstruction method from particles, sampling the water surface point by point. In addition to rendering the point based water surfaces, the use of the GPU permits efficient simulation of optical effects such as refraction, reflection, and caustics.

This paper describes a method for controlling the multi-phase smoke animation that uses Lagrangian particles. Previous methods need several density fields to simulate different types of smoke. We use a single field, which is more like a natural phenomenon to obtain the interactive motions of fluid. Also, whereas existing methods which apply control forces to cells only, we define particle forces which enable each particle to move independently towards to target shape. Additionally, we set up internal target forces which distribute the particles uniformly within the target shape, no that it is represented more precisely.