Abstract Designing realistic tridimensional facial models is a challenging task, not only due to the effort and artistic abilities required but also because human visual perception is very tuned to the processing of facial features. For this reason, rather than creating face models from scratch, artists usually start from a scanned model of a real person. In this work, we present a novel method for blending human faces in order to create a new one. In a nutshell, our proposal uses Laplacian smoothing to segregate layers of details from one or more faces, which are then integrated into a base face with the help of an interactive and visual editor. In particular, our method supports blending multiple faces and multiple sub‐regions in those faces. Since our approach is intuitive and relatively easy to implement, it can be integrated into artistic pipelines aiming at designing human face models from preexisting ones.

We propose QuadMixer, a novel interactive technique to compose quad mesh components preserving the majority of the original layouts. Quad Layout is a crucial property for many applications since it conveys important information that would otherwise be destroyed by techniques that aim only at preserving shape. Our technique keeps untouched all the quads in the patches which are not involved in the blending. We first perform robust boolean operations on the corresponding triangle meshes. Then we use this result to identify and build new surface patches for small regions neighboring the intersection curves. These blending patches are carefully quadrangulated respecting boundary constraints and stitched back to the untouched parts of the original models. The resulting mesh preserves the designed edge flow that, by construction, is captured and incorporated to the new quads as much as possible. We present our technique in an interactive tool to show its usability and robustness.

Abstract The hidden point removal (HPR) operator introduced by Katz et al. [KTB07] provides an elegant solution for the problem of estimating the visibility of points in point samplings of surfaces. Since the method requires computing the three‐dimensional convex hull of a set with the same cardinality as the original cloud, the method has been largely viewed as impractical for real‐time rendering of medium to large clouds. In this paper we examine how the HPR operator can be used more efficiently by combining several image space techniques, including an approximate convex hull algorithm, cloud sampling, and GPU programming. Experiments show that this combination permits faster renderings without overly compromising the accuracy.

Abstract We present an efficient Graphics Processing Unit GPU‐based implementation of the Projected Tetrahedra (PT) algorithm. By reducing most of the CPU–GPU data transfer, the algorithm achieves interactive frame rates (up to 2.0 M Tets/s) on current graphics hardware. Since no topology information is stored, it requires substantially less memory than recent interactive ray casting approaches. The method uses a two‐pass GPU approach with two fragment shaders. This work includes extended volume inspection capabilities by supporting interactive transfer function editing and isosurface highlighting using a Phong illumination model.

The topologically adaptable snake model, or simply T-snakes, is a useful tool for automatically identifying multiple segments in an image. According to A. Oliveira et al. (2004), a novel approach for controlling the topology of a T-snake was introduced. That approach focuses on the loops formed by the projected curve which is obtained at every stage of the snake evolution. The idea is to make that curve the image of a piecewise linear mapping of an adequate class. Then, with the help of an additional structure, the loop-tree, it is possible to decide in 0(1) time whether the region delimited by each loop has already been explored by the snake. In the original proposal of the loop snakes model, the snake evolution is limited to contraction and there is only one T-snake that contracts and splits during evolution. In this paper we generalize the original model by allowing the contraction as well as the expansion of several T-snakes.

The number of polygons in realistic architectural models is many more than can be rendered at interactive frame rates. Typically, however, due to occlusion by opaque surfaces (e.g., walls), only small fractions of such models are visible from most viewpoints. This fact is used in many popular methods for preprocessing visibility information which assume a scene model subdivided into convex cells connected through convex portals. These methods need to establish which cells or parts thereof are visible to a generalized observer located within each cell. The geometry of this information is termed a ‘visibility volume’ and its computation is usually quite complex. Conservative approximations of viewing volumes, however, are simpler and less expensive to compute. In this paper we present techniques and algorithms which permit the computation of conservative viewing volumes incrementally. In particular, we describe an algorithm for computing the viewing volumes for a given cell through a sequence of ‘m’ portals containing a total of ‘n’ edges in Omn time.

A new method termed the vertex representation is presented for approximating the shapes of objects of arbitrary dimensionality d (e.g., 2D, 3D, etc.) with orthogonal (d-1)-dimensional faces using a variable number of vertices. The vertex representation can be viewed as a generalization of boundary codes (i.e., chain codes) to higher dimensions. Techniques are described for using the vertex representation to efficiently perform many operations commonly performed on rasters. The utility of these techniques in image database applications is discussed.