PhD Defense : “Compression progressive de maillages surfaciques texturés”, Florian CAILLAUD
|Tuesday, janunary 17th 2017 – 9:30,
Room 337 Building Blaise Pascal,
INSA Lyon, 69100 VILLEURBANNE
|Since several years, 3D models become more and more detailed. This increases substantially the amount of data needed to describe them. However, in the same time, a rising number of applications are constrained in memory and/or in speed (mobile device
visualization, video games, etc.). These difficulties are even more visible within a Web context. This situation can lead to incompatibilities, latency in transmission or rendering,
which is generally an issue.
The progressive compression of these models is a possible solution. The goal is to compress the information (geometry, connectivity and associated attributes) in order to allow a progressive reconstruction of the mesh. Contrary to a single-rate compression,
progressive compression quickly proposes a faithful draft of the 3D model and, then, refines it until the complete mesh is recovered. This allows a better comfort for the user and a real adaptation of the rendered element number in adequacy with the terminal
The existing approaches for progressive compression mainly focus on triangular 2-manifold meshes. Very few methods are able to compress progressively non-manifold surface meshes and, to our knowledge, none can deal with every surface meshes (i.e. nomanifold
and polygonal), in a generic way. So as to suppress these limitations, we present a new generic progressive method allowing the compression of polygonal non-manifold surface meshes. Moreover, our approach takes care of the texture attribute, possibly associated to these meshes, by handling properly potential texture seams.
For that purpose, we progressively decimate the mesh using a new generic simplification operator. This decimation is driven by a local metric which aims to preserve both the geometry and the texture parametrisation. During the simplification, we progressively encode the necessary information for the reconstruction. In order to improve the compression rate, we propose several entropy reduction mechanisms, as well as geometry based prediction strategies for the connectivity and UV coordinates encoding. Finally, the texture map is progressively compressed then multiplexed with mesh data. This multiplexing is achieved using a perceptual metric to provide the best rate-distortion ratio as possible during the decompression.
PhD Defense : “Evaluationg the visibility threshold for a local geometric distorsion on a 3D mesh and its application”, Georges NADER
|Tuesday, november 22th 2016 – 10h00,
Room C4, building Nautibus,
Université Claude Bernard Lyon1, 69100 VILLEURBANNE
|Geometric operations applied to a 3D mesh introduce geometric distortion in the form of vertex displacement that can be visible to a human observer. In this thesis, we have studied the perceptual impact of these geometric distortions. More precisely, our goal is to compute the threshold beyond which a local geometric distortion becomes visible. In order to reach this goal, we start by evaluating perceptually relevant properties on 3D meshes. We have then performed a series of psychophysical experiments in which we measured the visibility threshold relative to various properties of the Human Visual System (contrast sensitivity and visual masking). The results of these experiments allowed us to propose an algorithm that computes the visibility threshold relative to a local geometric distortion. This algorithm is capable of adapting to the different display condition of 3D meshes (resolution, display size, illumination condition and rendering). Finally, we showcase the utility of our work by integrating the developed perceptual method in several geometric operations such as mesh simplification and adaptive subdivision.|
Pacific Graphics 2016 : Best Paper Award
|The paper “Visual Contrast Sensitivity and Discrimination for 3D Meshes and their Applications” from Georges Nader*, Kai Wang, Franck Hetroy-Wheeler and Florent Dupont* (*M2DisCo Team members) received the best paper award of the Pacific Graphics conference held in Okinawa (Japan) (2016 october 11-14).|
PhD Defense : “Contributions to Objective and Subjective Visual Quality Assessment of 3D Models”, Jinjinag GUO
|Thursday, october 6th 2016 – 10h30,
Amphi 337 – 3rd floor, building Blaise Pascal,
INSA Lyon,7 avenue Jean Capelle, 69100 VILLEURBANNE
|In computer graphics realm, three-dimensional graphical data, generally represented by triangular meshes, have become commonplace, and are deployed in a variety of application processes (e.g., smoothing, compression, remeshing, simplification, rendering, etc.). However, these processes inevitably introduce artifacts, altering the visual quality of the rendered 3D data. Thus, in order to perceptually drive the processing algorithms, there is an increasing need for efficient and effective subjective and objective visual quality assessments to evaluate and predict the visual artifacts. In this thesis, we first present a comprehensive survey on different sources of artifacts in digital graphics, and current objective and subjective visual quality assessments of the artifacts. Then, we introduce a newly designed subjective quality study based on evaluations of the local visibility of geometric artifacts, in which observers were asked to mark areas of 3D meshes that contain noticeable distortions. The collected perceived distortion maps are used to illustrate several perceptual functionalities of the human visual system (HVS), and serve as ground-truth to evaluate the performances of well-known geometric attributes and metrics for predicting the local visibility of distortions. Our second study aims to evaluate the visual quality of texture mapped 3D model subjectively and objectively. To achieve these goals, we introduced 116 processed models with both geometric and texture distortions, conducted a paired-comparison subjective experiment, and invited 98 subjects to evaluate the visual qualities of the models under two rendering protocols. Driven by the collected subjective opinions, we propose two objective visual quality metrics for textured meshes, relying on the optimal combinations of geometry and texture quality measures. These proposed perceptual metrics outperform their counterparts in term of the correlation with the human judgment.|
Four papers accepted to Pacific graphics 2016
|Three papers from the M2Disco team have been accepted as Full Papers to Pacific Graphics 2016 and will be published in Computer Graphic Forum.
One short paper has also been accepted.
|The DGtal project (http://dgtal.org) has received the software award at the Symposium on Geometry Processing 2016 (june 20th-24th, Berlin).|
|In the context of a collaboration between LIRIS, CEREMADE (Paris-Dauphine) and Kyoto University, Nicolas Bonneel will present his work on barycentric coordinates for histograms at SIGGRAPH 2016 in Anaheim (CA).|
|SIGGRAPH is a major annual event in computer graphics, organized by the ACM. This conference benefits from between 10 and 20 000 attendees – artists, researchers, companies – and represents every aspect of computer graphics: rendering, photography, 3D printing, animation etc. This year, Nicolas Bonneel has been selected by the AFIG and GDR IGRV to cover this event that will take place in Anaheim in California, from July 24th to 28th, 2016.|