Marcos Balsa Rodríguez

Adaptive quad patches: an adaptive regular structure for web distribution and adaptive rendering of 3D models

We introduce an approach for efficient distribution and adaptive rendering of 3D mesh models supporting a simple quad parameterization. Our method extends and combines recent results in geometric processing, real-time rendering, and web programming. In particular: we exploit recent results on surface reconstruction and isometric parametrization to transform point clouds into two-manifold meshes whose parametrization domain is a small collection of 2D square regions; we encode the resulting parameterized meshes into a very compact multiresolution structures composed of variable resolution quad patches whose geometry and texture is stored in a tightly packed texture atlas; we adaptively stream and render variable resolution shape representations using a GPU-accelerated adaptive tessellation algorithm with negligible CPU overhead. Real-time performance is achieved on portable GPU platforms using OpenGL, as well as on exploiting emerging web-based environments based on WebGL. Promising applications of the technology range from the automatic creation of rapidly renderable objects for games to the set-up of browsable 3D models repositories in the web that will be accessible by upcoming generation of WebGL-enabled web browers.

IsoCam: Interactive Visual Exploration of Massive Cultural Heritage Models on Large Projection Setups

We introduce a novel user interface and system for exploring extremely detailed 3D models in a museum setting. Three-dimensional models and associated information are presented on a large projection surface controlled by a touch-enabled surface placed at a suitable distance in front of it. Our indirect user interface, dubbed IsoCam, combines an object-aware interactive camera controller with an interactive point-of-interest selector and is implemented within a scalable implementation based on multiresolution structures shared between the rendering and user interaction subsystems. The collision-free camera controller automatically supports the smooth transition from orbiting to proximal navigation, by exploiting a distance-field representation of the 3D object. The point-of-interest selector exploits a specialized view similarity computation to propose a few nearby easily reachable interesting 3D views from a large database, move the camera to the user-selected point of interest, and provide extra information through overlaid annotations of the target view. The capabilities of our approach have been demonstrated in a public event attended by thousands of people, which were offered the possibility to explore submillimetric reconstructions of 38 stone statues of the Mont’e Prama Nuragic complex, depicting larger-than-life human figures, and small models of prehistoric Nuraghe (cone-shaped stone towers). A follow-up of this work, using 2.5m-high projection screens, is now included in permanent exhibitions at two Archeological Museums. Results of a thorough user evaluation, involving quantitative and subjective measurements, are discussed.

A Survey of Compressed GPU-Based Direct Volume Rendering

Great advancements in commodity graphics hardware have favored GPU-based volume rendering as the main adopted solution for interactive exploration of rectilinear scalar volumes on commodity platforms. Nevertheless, long data transfer times and GPU memory size limitations are often the main limiting factors, especially for massive, time-varying or multi-volume visualization, or for networked visualization on the emerging mobile devices. To address this issue, a variety of level-of-detail data representations and compression techniques have been introduced. In order to improve capabilities and performance over the entire storage, distribution and rendering pipeline, the encoding/decoding process is typically highly asymmetric, and systems should ideally compress at data production time and decompress on demand at rendering time. Compression and level-of-detail pre-computation does not have to adhere to real-time constraints and can be performed off-line for high quality results. In contrast, adaptive real-time rendering from compressed representations requires fast, transient, and spatially independent decompression. In this report, we review the existing compressed GPU volume rendering approaches, covering compact representation models, compression techniques, GPU rendering architectures and fast decoding techniques.

Compression-domain seamless multiresolution visualization of gigantic triangle meshes on mobile devices

We present a software architecture for distributing and rendering gigantic 3D triangle meshes on common handheld devices. Our approach copes with strong bandwidth and hardware capabilities limitations in terms with a compression-domain adaptive multiresolution rendering approach. The method uses a regular conformal hierarchy of tetrahedra to spatially partition the input 3D model and to arrange mesh fragments at different resolution. We create compact GPU-friendly representations of these fragments by constructing cache-coherent strips that index locally quantized vertex data, exploiting the bounding tetrahedron for creating local barycentic parametrization of the geometry. For the first time, this approach supports local quantization in a fully adaptive seamless 3D mesh structure. For web distribution, further compression is obtained by exploiting local data coherence for entropy coding. At run-time, mobile viewer applications adaptively refine a local multiresolution model maintained in a GPU by asynchronously loading from a web server the required fragments. CPU and GPU cooperate for decompression, and a shaded rendering of colored meshes is performed at interactive speed directly from an intermediate compact representation using only 8bytes/vertex, therefore coping with both memory and bandwidth limitations. The quality and performance of the approach is demonstrated with the interactive exploration of gigatriangle-sized models on common mobile platforms.

Practical Volume Rendering in mobile devices

Volume rendering has been a relevant topic in scientific visualization for the last two decades. A decade ago the exploration of reasonably big volume datasets required costly workstations due to the high processing cost of this kind of visualization. In the last years, a high end PC or laptop was enough to be able to handle medium-sized datasets thanks specially to the fast evolution of GPU hardware. New embedded CPUs that sport powerful graphics chipsets make complex 3D applications feasible in such devices. However, besides the much marketed presentations and all its hype, no real empirical data is usually available that makes comparing absolute and relative capabilities possible. In this paper we analyze current graphics hardware in most high-end Android mobile devices and perform a practical comparison of a well-known GPU-intensive task: volume rendering. We analyze different aspects by implementing three different classical algorithms and show how the current state-of-the art mobile GPUs behave in volume rendering.Volume rendering has been a relevant topic in scientific visualization for the last two decades. A decade ago the exploration of reasonably big volume datasets required costly workstations due to the high processing cost of this kind of visualization. In the last years, a high end PC or laptop was enough to be able to handle medium-sized datasets thanks specially to the fast evolution of GPU hardware. New embedded CPUs that sport powerful graphics chipsets make complex 3D applications feasible in such devices. However, besides the much marketed presentations and all its hype, no real empirical data is usually available that makes comparing absolute and relative capabilities possible. In this paper we analyze current graphics hardware in most high-end Android mobile devices and perform a practical comparison of a well-known GPU-intensive task: volume rendering. We analyze different aspects by implementing three different classical algorithms and show how the current state-of-the art mobile GPUs behave in volume rendering.

HuMoRS: huge models mobile rendering system

We present HuMoRS, a networked 3D graphics system for interactively streaming and exploring massive 3D mesh models on mobile devices. The system integrates a networked architecture for adaptive on-device rendering of multiresolution surfaces with a simple and effective interactive camera controller customized for touch-enabled mobile devices. During interaction, knowledge of the currently rendered scene is exploited to automatically center a rotation pivot and to propose context-dependent precomputed viewpoints. Both the object of interest and the viewpoint database are resident on a web server and adaptive transmission is demonstrated over wireless and phone connections in a Cultural Heritage application for the exploration of sub-millimetric colored reconstructions of stone statues. We report also on a preliminary user-study comparing the performances of our camera navigation method with respect to the most popular Virtual TrackBall implementations, with and without pivoting.

Interactive exploration of gigantic point clouds on mobile devices

New embedded CPUs that sport powerful graphics chipsets have the potential to make complex 3D applications feasible on mobile devices. In this paper, we present a scalable architecture and its implementation for mobile exploration of large point clouds, which are nowadays ubiquitous in the cultural heritage domain thanks to the increased performance and availability of 3D scanning techniques. The quality and performance of our approach is demonstrated on gigantic point clouds, interactively explored on Apple iPad and iPhone devices using in variety of network settings. Applications of the technology include on-site exploration during scanning campaigns and promotion of cultural heritage artifacts.

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.

Digital Mont’e Prama: Exploring Large Collections of Detailed 3D Models of Sculptures

We present and evaluate a scalable interactive system for the exploration of large collections of detailed three-dimensional digital models of sculptures. The system has been applied to the valorization of the Mont’e Prama complex, an extraordinary collection of protostoric Mediterranean sculptures, which depict models of cone-shaped stone towers, as well as larger-than-life human figures. The software architecture is based on scalable components for efficient distribution and adaptive rendering of extremely detailed surface meshes with overlaid information. The user interface, based on a simple and effective interactive camera controller tailored for touch interaction, has been designed for targeting both small screens and large display systems. The system components have been integrated in different interactive applications, ranging from large-screen museum setups and low-end mobile devices both with very high visual quality. The large-scale system has been installed in a variety of temporal and permanent exhibitions and has been extensively used by tens of thousands of visitors. We provide an early analysis in this article of the data gathered during a 20-month period in the National Archaeological Museum in Cagliari and a 6-month period in the Civic Museum in Cabras, for a total of over 67,000 exploration sessions.

Coarse-grained multiresolution structures for mobile exploration of gigantic surface models

We discuss our experience in creating scalable systems for distributing and rendering gigantic 3D surfaces on web environments and common handheld devices. Our methods are based on compressed streamable coarse-grained multiresolution structures. By combining CPU and GPU compression technology with our multiresolution data representation, we are able to incrementally transfer, locally store and render with unprecedented performance extremely detailed 3D mesh models on WebGL-enabled browsers, as well as on hardware-constrained mobile devices.