Abstract 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 © 2004 John Wiley & Sons, Ltd.

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.

The 3D reconstruction of the cerebral vascular anatomy can greatly improve the diagnosis of vascular pathologies, such as embolisms and haemorrhages. This paper presents a new method for the automatic extraction of the blood vessels surface and the labelling of its features, specifically branching, aneurysms and stenoses. The method works with segmented magnetic resonance angiography images. It extracts a discrete medial axis transform from the stacked images and vectorizes it. During the vectorization process, the features are detected and labelled automatically. The final output is a labelled continuous medial axis transform representation of the vascular tree suitable for interactive visualizations and navigations, along with 3D geometrical and topological queries.

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.

An interactive cerebral blood vessel exploration system is described. It has been designed on the basis of neurosurgeons' requirements in order to assist them in the diagnosis of vascular pathologies. The system is based on the construction of a symbolic model of the vascular tree, with automatic identification and labelling of vessel bifurcations, aneurysms and stenoses. It provides several types of visualization: individual MRA (magnetic resonance angiography) slices, MIP (maximum intensity projection), shaded rendering, symbolic schemes and surface reconstruction.

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 object's 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. © 1997 John Wiley & Sons, Ltd.

Abstract A survey on computer animation is presented with three specific goals: To clarify what people understand by computer animation. To separate the different aspects of computer animation and underline its main problems. To present the different solutions given to these problems. Several classifications for computer animation systems are first made attending to different criteria. The report is subsequently divided into two basic sections according to the historical classification of computer animation systems: computer‐assisted animation, where traditional animation is just helped by the use of computers, and modelled animation where the use of computers is essential in different aspects of the animation process. Special emphasis is placed on motion specification and generation. Finally, special attention is paid to human body animation because of the great interest of this specific field of computer animation and the peculiarity of its problems. Aspects of hardware aspects and postprocessing has just been taken into account in the classification section but have not been studied.