Haptic interfaces offer an intuitive way to interact with and manipulate 3D datasets, and may simplify the interpretation of visual information. This work proposes an algorithm to provide haptic feedback directly from volumetric datasets, as an aid to regular visualization. The haptic rendering algorithm lets users perceive isosurfaces in volumetric datasets, and it relies on several design features that ensure a robust and efficient rendering. A marching tetrahedra approach enables the dynamic extraction of a piecewise linear continuous isosurface. Robustness is achieved using a continuous collision detection step coupled with state-of-the-art proxy-based rendering methods over the extracted isosurface. The introduced marching tetrahedra approach guarantees that the extracted isosurface will match the topology of an equivalent isosurface computed using trilinear interpolation. The proposed haptic rendering algorithm improves the consistency between haptic and visual cues computing a second proxy on the isosurface displayed on screen. Our experiments demonstrate the improvements on the isosurface extraction stage as well as the robustness and the efficiency of the complete algorithm.

Dendritic spines are thin protrusions that cover the dendritic surface of numerous neurons in the brain and whose function seems to play a key role in neural circuits. The correct segmentation of those structures is difficult due to their small size and the resulting spines can appear incomplete. This paper presents a four-step procedure for the complete reconstruction of dendritic spines. The haptically driven procedure is intended to work as an image processing stage before the automatic segmentation step giving the final representation of the dendritic spines. The procedure is designed to allow both the navigation and the volume image editing to be carried out using a haptic device. A use case employing our procedure together with a commercial software package for the segmentation stage is illustrated. Finally, the haptic editing is evaluated in two experiments; the first experiment concerns the benefits of the force feedback and the second checks the suitability of the use of a haptic device as input. In both cases, the results shows that the procedure improves the editing accuracy.

When we create an environment of virtual reality based training that integrates one or several haptic devices sometimes the first choice to make is the device to use. This paper introduces an algorithm that allows us, for a particular task to be simulated in a virtual environment, to find key data for the design of appropriate haptic device, or to select the clues in order to get optimum performance for that environment and that particular task.

Haptic interfaces offer an intuitive way to interact with and manipulate 3D data, and may simplify the interpretation of visual information. This work proposes an algorithm to provide haptic feedback directly from volumetric data sets, as an aid to regular visualization. The haptic rendering algorithm lets the user perceive isosurfaces in the volumetric data, and it relies on several design features that ensure a robust and efficient rendering. Robustness is derived from existing proxy-based methods. The presented algorithm adds a novel continuous collision detection based on dynamic extraction of isosurfaces in tetrahedral meshes in order to avoid fall-through of surfaces. The isosurface is extracted dynamically in a local manner, hence there is no need to construct and store the full isosurface, thereby reducing both computational cost and storage at the same time. Isosurfaces are defined by interpolating a density field on tetrahedral meshes. The use of tetrahedral meshes guarantees continuity and watertightness of the isosurface, and it also enables smooth transitions between isosurface values.