Dani Tost

Human body animation: a survey

A survey of human body animation is presented dealing with its geometrical representation, motion control techniques and rendering. A classification of human body animation systems is presented according to different criteria.The human body movement notations are described and the different existing geometric models of the body and the face are analised and compared.The body and face control motion techniques are presented and discussed, as well as human body motion in its environment. Finally, the different problems of human body rendering are presented.

A framework for fusion methods and rendering techniques of multimodal volume data

Many different direct volume rendering methods have been developed to visualize 3D scalar fields on uniform rectilinear grids. However, little work has been done on rendering simultaneously various properties of the same 3D region measured with different registration devices or at different instants of time. The demand for this type of visualization is rapidly increasing in scientific applications such as medicine in which the visual integration of multiple modalities allows a better comprehension of the anatomy and a perception of its relationships with activity. This paper presents different strategies of direct multimodal volume rendering (DMVR). It is restricted to voxel models with a known 3D rigid alignment transformation. The paper evaluates at which steps of the rendering pipeline the data fusion must be realized in order to accomplish the desired visual integration and to provide fast re‐renders when some fusion parameters are modified. In addition, it analyses how existing monomodal visualization algorithms can be extended to multiple datasets and it compares their efficiency and their computational cost. Copyright

Frame-to-frame coherent animation with two-pass radiosity

This paper proposes an efficient method for the production of high quality radiosity solutions which uses an a priori knowledge of the dynamic properties of the scene to exploit temporal coherence. The method is based on a two-pass strategy that provides user-control on the final frame quality. In the first pass, it computes a coarse global solution of the radiosities along a time interval and then, in the second pass, it performs a frame-to-frame incremental gathering step using hardware graphic accelerators. Computing cost is thus reduced because the method takes advantage of frame-to-frame coherence by identifying the changes produced by dynamic objects and by decoupling them from computations that remain unchanged. The input data is a dynamic model of the environment through a period of time corresponding to the same camera recording. The method proceeds by incrementally updating two data structures: a space-time hierarchical radiosity solution for a given interval of time and a hierarchical tree of textures representing the space-time final illumination of the visible surfaces. These data structures are computed for a given viewpoint, either static or dynamic. The main contribution of this work is the efficient construction of the texture tree by identifying the changes produced by dynamic objects and by only recomputing these changes.

3D simulation of tool machining

Abstract This paper describes a 3D tool machining simulation system. The initial tool and the grinding wheels are integrated with the machine tool. The application reads and interprets the CNC program code that controls the machine, it computes the positions and the motion of components and it translates the sequence of machining operations into Boolean operations. The machining is computed for 2D sections and, later, a 3D model of the tool is reconstructed. The application is ready to yield tool visualization, it gives measurements on sections and it can show an interactive animation of the whole process. A novel aspect of the simulation is that it is able to deal with 6-axes machines, whereas most of previous work is limited to 3- and 4-axes machines. In addition, it allows to interrupt the machining process and to show partially machined tools. A major contribution is the fact that the Boolean operations are performed in 2D and the 3D model is reconstructed from the cross sections, which provides user control on the resolution of the operations at a low cost.

3D reconstruction and quantification of porous structures

In this paper, we describe the methodology that we have designed to quantify the pores distribution in bone implants and the empirical results that we have obtained with BioCAD designed scaffolds, microCT and confocal microscopy data. Our method is based on 3D digital topology properties of the porous structure. We segment the 3D images into three regions: exterior, bone and pore space. Next, we divide the pore space into pores and connection paths. We compute a graph of the pore space such that each node of the graph represents a pore, and an arc between two nodes indicates that the two pores are path-connected. On the basis of the graph and the segmented model, we are able to compute several properties of the material such as global porosity, effective porosity and radial pore distribution.

A GPU-driven algorithm for accurate interactive reflections on curved objects

We present a GPU-driven method for the fast computation of specular reflections on curved objects. For every reflector of the scene, our method computes a virtual object for every other object reflected in it. This virtual reflected object is then rendered and blended with the scene. For each vertex of each virtual object, a reflection point is found on the reflectors surface. This point is used to find the reflected virtual vertex, enabling the reflected virtual scene to be rendered. Our method renders the 3D points and normals of the reflector into textures, and uses a local search in a fragment program on the GPU to find the reflection points. By reorganizing the data and the computation in this manner, and correctly treating special cases, we make excellent use of the parallelism and stream-processing power of the GPU. In our results we show that, with our method, we can display high-quality reflections of nearby objects interactively.

Radiosity for dynamic environments

In this paper we present a radiosity algorithm for dynamic scenes with a high level of frame-to-frame coherence. The algorithm is restricted to dynamic environments, where the objects movement is known a priori and the viewpoint is static. Each image is computed as the sum of two images: the base-level image, computed in a pre-process, and the frame-level image computed incrementally at each frame. The computation of the images is based on an importance-driven heuristic approach. The results of the implementation are analysed and discussed.

PREVIRNEC: A cognitive telerehabilitation system based on Virtual Environments

In this paper, we describe PREVIRNEC, a distributed system for cognitive telerehabilitation based on virtual environments. Our system allows personalized treatments by means of 2D and 3D exercises that can be built according to single patients characteristics. Patients realize their exercises remotely. Depending on their obtained results, the system readjusts automatically the levels of difficulty of the tasks, and switches from one task to the other. The paper focuses on technological issues of the system design. We analyze its structure, components, and we discuss the decisions adopted in the interaction mode design and well as in the tasks layout.

Decision trees for accelerating unimodal, hybrid and multimodal rendering models

This paper deals with the rendering of segmented unimodal, hybrid and aligned multimodal voxel models. We propose a data structure that classifies the segmented voxels into categories, so that whenever the model has to be traversed, only the selected categories are visited and the empty and non-selected voxels are skipped. This strategy is based on: (i) a decision tree, called the rendering decision tree (RDT), which represents the hierarchy of the classification process and (ii) an intermediate run-length encoding (RLE) of the classified voxel model. The traversal of the voxel model given a user query consists of two steps: first, the RDT is traversed and the set of selected categories computed; next, the RLE is visited, but the non-selected runs are skipped and only the voxels of the original model that are codified are accessed in selected runs of the RLE. This strategy has been used to render a voxel model by back-to-front traversal and splatting as well as to construct 3D textures for hardware-driven 3D texture mapping. The results show that the voxel model traversal is significantly accelerated.

A Two-Pass Hardware-Based Method for Hierarchical Radiosity

Finite elements methods for radiosity are aimed at computing global illumination solutions efficiently. However these methods are not suitable for obtaining high quality images due to the lack of error control. Two‐pass methods allow to achieve that level of quality computing illumination at each pixel and thus introducing a high computing overhead. We present a two‐pass method for radiosity that allows to produce high quality images avoiding most of the per‐pixel computations. The method computes a coarse hierarchical radiosity solution and then performs a second pass using current graphics hardware accelerators to generate illumination as high definition textures.