Mobile graphics: SIGGRAPH Asia 2017 course

Peer ReviewedPostprint (published version

View-dependent Exploration of Massive Volumetric Models on Large Scale Light Field Displays

We report on a light-field display based virtual environment enabling multiple naked-eye users to perceive detailed multi-gigavoxel volumetric models as floating in space, responsive to their actions, and delivering different information in different areas of the workspace. Our contributions include a set of specialized interactive illustrative techniques able to provide different contextual information in different areas of the display, as well as an out-of-core CUDA based raycasting engine with a number of improvements over current GPU volume raycasters. The possibilities of the system are demonstrated by the multi-user interactive exploration of 64GVoxels datasets on a 35MPixel light field display driven by a cluster of PCs.1037-1047Pubblicat

Real-time GPU-accelerated Out-of-Core Rendering and Light-field Display Visualization for Improved Massive Volume Understanding

Nowadays huge digital models are becoming increasingly available for a number of different applications ranging from CAD, industrial design to medicine and natural sciences. Particularly, in the field of medicine, data acquisition devices such as MRI or CT scanners routinely produce huge volumetric datasets. Currently, these datasets can easily reach dimensions of 1024^3 voxels and datasets larger than that are not uncommon. This thesis focuses on efficient methods for the interactive exploration of such large volumes using direct volume visualization techniques on commodity platforms. To reach this goal specialized multi-resolution structures and algorithms, which are able to directly render volumes of potentially unlimited size are introduced. The developed techniques are output sensitive and their rendering costs depend only on the complexity of the generated images and not on the complexity of the input datasets. The advanced characteristics of modern GPGPU architectures are exploited and combined with an out-of-core framework in order to provide a more flexible, scalable and efficient implementation of these algorithms and data structures on single GPUs and GPU clusters. To improve visual perception and understanding, the use of novel 3D display technology based on a light-field approach is introduced. This kind of device allows multiple naked-eye users to perceive virtual objects floating inside the display workspace, exploiting the stereo and horizontal parallax. A set of specialized and interactive illustrative techniques capable of providing different contextual information in different areas of the display, as well as an out-of-core CUDA based ray-casting engine with a number of improvements over current GPU volume ray-casters are both reported. The possibilities of the system are demonstrated by the multi-user interactive exploration of 64-GVoxel datasets on a 35-MPixel light-field display driven by a cluster of PCs. ------------------------------------------------------------------------------------------------------ Negli ultimi anni si sta verificando una proliferazione sempre più consistente di modelli digitali di notevoli dimensioni in campi applicativi che variano dal CAD e la progettazione industriale alla medicina e le scienze naturali. In modo particolare, nel settore della medicina, le apparecchiature di acquisizione dei dati come RM o TAC producono comunemente dei dataset volumetrici di grosse dimensioni. Questi dataset possono facilmente raggiungere taglie dell’ordine di 10243 voxels e dataset di dimensioni maggiori possono essere frequenti. Questa tesi si focalizza su metodi efficienti per l’esplorazione di tali grossi volumi utilizzando tecniche di visualizzazione diretta su piattaforme HW di diffusione di massa. Per raggiungere tale obiettivo si introducono strutture specializzate multi-risoluzione e algoritmi in grado di visualizzare volumi di dimensioni potenzialmente infinite. Le tecniche sviluppate sono “ouput sensitive” e la loro complessità di rendering dipende soltanto dalle dimensioni delle immagini generate e non dalle dimensioni dei dataset di input. Le caratteristiche avanzate delle architetture moderne GPGPU vengono inoltre sfruttate e combinate con un framework “out-of-core” in modo da offrire una implementazione di questi algoritmi e strutture dati più flessibile, scalabile ed efficiente su singole GPU o cluster di GPU. Per migliorare la percezione visiva e la comprensione dei dati, viene introdotto inoltre l’uso di tecnologie di display 3D di nuova generazione basate su un approccio di tipo light-field. Questi tipi di dispositivi consentono a diversi utenti di percepire ad occhio nudo oggetti che galleggiano all’interno dello spazio di lavoro del display, sfruttando lo stereo e la parallasse orizzontale. Si descrivono infine un insieme di tecniche illustrative interattive in grado di fornire diverse informazioni contestuali in diverse zone del display, così come un motore di “ray-casting out-of-core” basato su CUDA e contenente una serie di miglioramenti rispetto agli attuali metodi GPU di “ray-casting” di volumi. Le possibilità del sistema sono dimostrate attraverso l’esplorazione interattiva di dataset di 64-GVoxel su un display di tipo light-field da 35-MPixel pilotato da un cluster di PC

Recent results in rendering massive models on horizontal parallax-only light field displays

In this contribution, we report on specialized out-of-core multiresolution real-time rendering systems able to render massive surface and volume models on a special class of horizontal parallax-only light field displays. The displays are based on a specially arranged array of projectors emitting light beams onto a holographic screen, which then makes the necessary optical transformation to compose these beams into a continuous 3D view. The rendering methods employ state-of-the-art out-of-core multiresolution techniques able to correctly project geometries onto the display and to dynamically adapt model resolution by taking into account the particular spatial accuracy characteristics of the display. The programmability of latest generation graphics architectures is exploited to achieve interactive performance. As a result, multiple freely moving naked-eye viewers can inspect and manipulate virtual 3D objects that appear to them floating at fixed physical locations. The approach provides rapid visual understanding of complex multi-gigabyte surface models and volumetric data sets.304-30

Hybrid Sample-based Surface Rendering

The performance of rasterization-based rendering on current GPUs strongly depends on the abilities to avoid overdraw and to prevent rendering triangles smaller than the pixel size. Otherwise, the rates at which highresolution polygon models can be displayed are affected significantly. Instead of trying to build these abilities into the rasterization-based rendering pipeline, we propose an alternative rendering pipeline implementation that uses rasterization and ray-casting in every frame simultaneously to determine eye-ray intersections. To make ray-casting competitive with rasterization, we introduce a memory-efficient sample-based data structure which gives rise to an efficient ray traversal procedure. In combination with a regular model subdivision, the most optimal rendering technique can be selected at run-time for each part. For very large triangle meshes our method can outperform pure rasterization and requires a considerably smaller memory budget on the GPU. Since the proposed data structure can be constructed from any renderable surface representation, it can also be used to efficiently render isosurfaces in scalar volume fields. The compactness of the data structure allows rendering from GPU memory when alternative techniques already require exhaustive paging

Ubiquitous volume rendering in the web platform

176 p.The main thesis hypothesis is that ubiquitous volume rendering can be achieved using WebGL. The thesis enumerates the challenges that should be met to achieve that goal. The results allow web content developers the integration of interactive volume rendering within standard HTML5 web pages. Content developers only need to declare the X3D nodes that provide the rendering characteristics they desire. In contrast to the systems that provide specific GPU programs, the presented architecture creates automatically the GPU code required by the WebGL graphics pipeline. This code is generated directly from the X3D nodes declared in the virtual scene. Therefore, content developers do not need to know about the GPU.The thesis extends previous research on web compatible volume data structures for WebGL, ray-casting hybrid surface and volumetric rendering, progressive volume rendering and some specific problems related to the visualization of medical datasets. Finally, the thesis contributes to the X3D standard with some proposals to extend and improve the volume rendering component. The proposals are in an advance stage towards their acceptance by the Web3D Consortium

CYBERSAR

The project aims at setting up an advanced cyberinfrastructure based on dedicated optical networks to support collaborative research application. The aim of Cybersar computational infrastructure is to support innovative computational applications by using leading edge hardware and technological solutions and to provide an experimental platform for research on the enabling technologies that will power next generation cyberinfrastructures. In particular, in the Visual Computing Group, we study techniques for processing and rendering very large scale 3D datasets on innovative large scale displays.Completato€ 1.291.50

Advances in massive model visualization in the CYBERSAR project

We provide a survey of the major results obtained within the CYBERSAR project in the area of massive data visualization. Despite the impressive improvements in graphics and computational hardware performance, interactive visualization of massive models still remains a challenging problem. To address this problem, we developed methods that exploit the programmability of latest generation graphics hardware, and combine coarse-grained multiresolution models, chunk-based data management with compression, incremental view-dependent level-of-detail selection, and visibility culling. The models that can be interactively rendered with our methods range from multi-gigabyte-sized datasets for general 3D meshes or scalar volumes, to terabyte-sized datasets in the restricted 2.5D case of digital terrain models. Such a performance enables novel ways of exploring massive datasets. In particular, we have demonstrated the capability of driving innovative light field displays able of giving multiple freely moving naked-eye viewers the illusion of seeing and manipulating massive 3D objects with continuous viewer-independent parallax.233-23