Exploring virtual prototypes using time-critical rendering techniques

Scientists at CRS4, the Center for Advanced Studies, Research and Development in Cagliari, Sardinia, Italy, have developed a time-critical rendering algorithm that relies upon a scene description in which objects are represented as multiresolution meshes. In collaboration with other European partners, this technique has been applied to the visual and collaborative exploration of large digital mock-ups.Pubblicat

Interactive inspection of complex multi-object industrial assemblies

The final publication is available at Springer via http://dx.doi.org/10.1016/j.cad.2016.06.005The use of virtual prototypes and digital models containing thousands of individual objects is commonplace in complex industrial applications like the cooperative design of huge ships. Designers are interested in selecting and editing specific sets of objects during the interactive inspection sessions. This is however not supported by standard visualization systems for huge models. In this paper we discuss in detail the concept of rendering front in multiresolution trees, their properties and the algorithms that construct the hierarchy and efficiently render it, applied to very complex CAD models, so that the model structure and the identities of objects are preserved. We also propose an algorithm for the interactive inspection of huge models which uses a rendering budget and supports selection of individual objects and sets of objects, displacement of the selected objects and real-time collision detection during these displacements. Our solution–based on the analysis of several existing view-dependent visualization schemes–uses a Hybrid Multiresolution Tree that mixes layers of exact geometry, simplified models and impostors, together with a time-critical, view-dependent algorithm and a Constrained Front. The algorithm has been successfully tested in real industrial environments; the models involved are presented and discussed in the paper.Peer ReviewedPostprint (author's final draft

Time-critical multiresolution rendering of large complex models

Very large and geometrically complex scenes, exceeding millions of polygons and hundreds of objects, arise naturally in many areas of interactive computer graphics. Time-critical rendering of such scenes requires the ability to trade visual quality with speed. Previous work has shown that this can be done by representing individual scene components as multiresolution triangle meshes, and performing at each frame a convex constrained optimization to choose the mesh resolutions that maximize image quality while meeting timing constraints. In this paper we demonstrate that the nonlinear optimization problem with linear constraints associated to a large class of quality estimation heuristics is efficiently solved using an active-set strategy. By exploiting the problem structure, Lagrange multipliers estimates and equality constrained problem solutions are computed in linear time. Results show that our algorithms and data structures provide low memory overhead, smooth level-of-detail control, and guarantee, within acceptable limits, a uniform, bounded frame rate even for widely changing viewing conditions. Implementation details are presented along with the results of tests for memory needs, algorithm timing, and efficacy.785-803Pubblicat

TOM: totally ordered mesh. A multiresolution data structure for time-critical graphics applications

Tridimensional interactive applications are confronted to situations where very large databases have to be animated, transmitted and displayed in very short bounded times. As it is generally impossible to handle the complete graphics description while meeting timing constraint, techniques enabling the extraction and manipulation of a significant part of the geometric database have been the focus of many research works in the field of computer graphics. Multiresolution representations of 3D models provide access to 3D objects at arbitrary resolutions while minimizing appearance degradation. Several kinds of data structures have been recently proposed for dealing with polygonal or parametric representations, but where not generally optimized for time-critical applications. We describe the TOM (Totally Ordered Mesh), a multiresolution triangle mesh structure tailored to the support of time-critical adaptive rendering. The structure grants high speed access to the continuous levels of detail of a mesh and allows very fast traversal of the list of triangles at arbitrary resolution so that bottlenecks in the graphic pipeline are avoided. Moreover, and without specific compression, the memory footprint of the TOM is small (about 108% of the single resolution object in face-vertex form) so that large scenes can be effectively handled. The TOM structure also supports storage of per vertex (or per corner of triangle) attributes such as colors, normals, texture coordinates or dynamic properties. Implementation details are presented along with the results of tests for memory needs, approximation quality, timing and efficacy

Multiresolution Foliage Rendering

Ponència presentada en CoSECiVi 2020, VI Congreso de la Sociedad Española para las Ciencias del Videojuego On-line, 7-8 d'octubre de 2020.This work presents a continuous level of detail representation of foliage of trees. Multiresolution modeling allows to adapt the number of polygons to render to the relevance of the object in the scene. However, foliage is represented by isolated polygons, so most of the multiresolution modeling methods do not work properly with this part of the tree. This paper presents a multiresolution model that allows to adapt the number of leaves to the relevance of the foliage in the scene. The criterion to select the appropriate leaves to render is based on a previously performed view-driven simplification. To adapt this parameter in real time, data structures and the necessary algorithms that allow us to extract the appropriate number of polygons are presented. Some tests have been developed to evaluate the proposed solution and results show the good performance of the presented continuous level of detail

Real-time Photorealistic Visualisation of Large-scaleMultiresolution Terrain Models

Height field terrain rendering is an important aspect of GIS, outdoor virtual reality applicationssuch as flight simulation, 3-D games, etc. A polygonal model of very large terrain data requiresa large number of triangles. So, even most high-performance graphics workstations have greatdifficulty to display even moderately sized height fields at interactive frame rates. To bringphotorealism in visualisation, it is required to drape corresponding high-resolution satellite oraerial phototexture over 3-D digital terrain and also to place multiple collections of point-location-based static objects such as buildings, trees, etc and to overlay polyline vector objects suchas roads on top of the terrain surface. It further complicates the requirement of interactive framerates while navigation over the terrain. This paper describes a novel approach for objects andterrain visualisation by combination of two algorithms, one for terrain data and the other forobjects. The terrain rendering is accomplished by an efficient dynamic multiresolution view-dependent level-of-detail mesh simplification algorithm. It is augmented with out-of-corevisualisation of large-height geometry and phototexture terrain data populated with 3-D/2-Dstatic objects as well as vector overlays without extensive memory load. The proposedmethodology provides interactive frame rates on a general-purpose desktop PC with OpenGL-enabled graphics hardware. The software TREND has been successfully tested on different real-world height maps and satellite phototextures of sizes up to 16K*16K coupled with thousandsof static objects and polyline vector overlays

Interactive Out-of-core Visualization of Very Large Landscapes on Commodity Graphics Platforms

We recently introduced an efficient technique for out-of-core rendering and management of large textured landscapes. The technique, called Batched Dynamic Adaptive Meshes (BDAM), is based on a paired tree structure: a tiled quadtree for texture data and a pair of bintrees of small triangular patches for the geometry. These small patches are TINs that are constructed and optimized off-line with high quality simplification and tristripping algorithms. Hierarchical view frustum culling and view-dependendent texture/geometry refinement is performed at each frame with a stateless traversal algorithm that renders a continuous adaptive terrain surface by assembling out of core data. Thanks to the batched CPU/GPU communication model, the proposed technique is not processor intensive and fully harnesses the power of current graphics hardware. This paper summarizes the method and discusses the results obtained in a virtual flythrough over a textured digital landscape derived from aerial imaging.21-2

Distribución y uso de modelos 3D en la web: ¿estamos listos?

[EN] Digital technologies are now mature for producing high quality digital replicas of Cultural Heritage (CH) assets. The research results produced in the last decade ignitedan impressive evolution and consolidation of the technologies for acquiring high-quality digital three-dimensional (3D)models, encompassing both geometry and color. What remains still an open problem is how to deliver those data and related knowledge to our society. The web is nowadays the main channel for the dissemination of knowledge. Emerging commercial solutions for web-publishing of 3D data are consolidating and becoming a de-facto standard for many applications(e-commerce, industrial products, education, etc.).In this framework, CH is a very specific domain, requiring highly flexible solutions. Some recent experiences arepresented, aimed at providing a support to the archival of archaeological3Ddata, supporting web-based publishing of very high-resolution digitization results and finally enabling the documentation of complex restoration actions. All those examples have been recently implemented on the open-source 3D Heritage Online Presenter (3DHOP)platform, developed at CNR-ISTI[ES] Las tecnologías digitales estánahora maduraspara producir réplicas digitales de alta calidad de valores activos del patrimonio cultural (CH). Los resultados de la investigación producidos en la última década han mostrado una evolución impresionante y una consolidación de las tecnologías para la capturade modelos digitales tridimensionales (3D)de alta calidad, que abarcanla geometríay el color.Lo que queda aún por resolver estárelacionado con la forma de distribuirlos datos y el conocimiento relacionado conla sociedad. La web es hoy en día el principal canal utilizado para divulgarel conocimiento. Las soluciones comerciales nuevas relacionadas con la publicación en la red de datos en 3D se están consolidando y convirtiendo en un estándar de facto para muchas aplicaciones(comercio electrónico, productos industriales, educación, etc.). En este escenario, el patrimonio culturales un dominio muy específico, que requiere soluciones muyflexibles.Se presentan algunas experiencias recientes, destinadasa proporcionar un apoyo al archivo de los datos arqueológicos3D, la publicaciónwebde los resultados de digitalización de muy alta resoluciónque permitenfinalmente la documentación de trabajos de restauracióncomplejos. Todos estos ejemplos se han implementado recientemente en la plataforma 3D Heritage Online Presenter(3DHOP)de código abierto, desarrolladaen el CNR-ISTI.The research leading to these results has received funding from the EU 7th Framework Programme (FP7/2007-2013) under grant agreement no. 654119 (EC "PARTHENOS" project) and EU H2020 Programme (“EMOTIVE: EMOTIve Virtual cultural Experiences through personalized storytelling”, H2020-SC6-CULT-COOP-08-2016) under grant agreement no. 727188.Scopigno, R.; Callieri, M.; Dellepiane, M.; Ponchio, F.; Potenziani, M. (2017). Delivering and using 3D models on the web: are we ready?. Virtual Archaeology Review. 8(17):1-9. https://doi.org/10.4995/var.2017.6405SWORD1981