Marco Agus

Physics-based burr haptic simulation: tuning and evaluation

In this paper we provide a preliminary report on our work on the tuning of a temporal bone surgical simulator using parameter values derived from experimental measurements, and on the comparison between these results and the previously used domain expert assigned values. Our preliminary results indicate that the parameter values defined by the domain-experts are consistent with the experimentally derived values. Psychophysical testing indicates that the simulator is capable of rendering the basic material differences required for bone burring work and that some trained users preferentially associate a simulated temporal bone resin model with its real counterpart.

Digital Mont'e Prama: 3D Cultural Heritage presentations in museums and anywhere.

We present an interactive visualization system developed for the valorization of an extraordinary collection of protostoric Mediterranean sculptures, which depict models of buildings (cone-shaped stone towers), as well as larger-than-life human figures. The architecture is based on scalable components for efficient distribution and adaptive rendering of extremely detailed surface meshes, as well as a simple and effective interactive camera controller tailored for touch interaction. The user interface has been designed for targeting both small screens and large display systems, and in a way that casual users can easily and naturally explore the models with fast learning curves. Furthermore, a thumbnail-based point-of-interest selector enable users to explore 3D views with information presented as 2D overlays decorating the 3D scene. The system components have been integrated in different interactive applications, ranging from large-screen museal setups and low end mobile devices both with very high visual quality. The capabilities of the museal systems have been demonstrated in a variety of temporal and permanent exhibitions, where they have been extensively used by tens of thousands of visitors.

Split-voxel: a simple discontinuity-preserving voxel representation for volume rendering

The most common representation of volumetric models is a regular grid of cubical voxels with one value each, from which a smooth scalar field is reconstructed. However, common real-world situations include cases in which volumes represent physical objects with well defined boundaries separating different materials, giving rise to models with quasi-impulsive gradient fields. In our split-voxel representation, we replace blocks of N3 voxels by one single voxel that is split by a feature plane into two regions with constant values. This representation has little overhead over storing precomputed gradients, and has the advantage that feature planes provide minimal geometric information about the underlying volume regions that can be effectively exploited for volume rendering. We show how to convert a standard mono-resolution representation into a out-of-core multiresolution structure, both for labeled and continuous scalar volumes. We also show how to interactively explore the models using a multiresolution GPU raycasting framework. The technique supports real-time transfer function manipulation and proves particularly useful for fast multiresolution rendering, since accurate silhouettes are preserved even at very coarse levels of detail.

Automatic geometric calibration of projector-based light-field displays

We present a novel calibration method for continuous multiview (light field) projection-based displays using a single uncalibrated camera and four fiducial markers. Calibration starts from a simple parametric description of the display layout. First, individual projectors are calibrated through parametric optimization of an idealized pinhole model. Then, the overall display and projector parameterization is globally optimized. Finally, independently for each projector, remaining errors are corrected through a rational 2D warping function. The final parameters are available to rendering engines to quickly compute forward and backward projections. The technique is demonstrated in the calibration of a large-scale horizontal-parallax-only 35MPixels light field display.