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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<meta name="keywords" content="andreas,vasilakis,professor,phd,postdoc,fudos,uoi,aueb,abasilak,ioannina,athens,corfu,gepap,certh,iti,moustakas,scagja,multi-fragment,multifragment,rendering,depth,peeling,a-buffer,rayground,k-buffer,webrays,s-buffer,csg,opengl,vulkan,think-silicon,glove,phasmatic" />
<meta name="description" content="Andreas A. Vasilakis personal web site" />
<meta http-equiv="refresh" content="0; url=https://graphics.cs.aueb.gr/users/abasilak/">
<title>A.A. Vasilakis Personal Site</title>
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<body>
<!--
<div class="container">
<hr>
<div id="init" class="row">
<div class="col-sm-3">
<a href="https://www.flickr.com/photos/abasilak/"> <img class="shadow fig-rounded center-block" src="images/me.jpg" alt="andreas vasilakis photo" title="abasilak"> </a>
</div>
<div class="col-sm-9">
<h1 class="text-center">Andreas A. Vasilakis</h1>
<h4 class="text-center">Co-founder / Computer Graphics R&D / Adjunct Professor</h4>
<h4 class="text-center">Phasmatic / Athens University of Economics and Business, Greece</h4>
<table style="width:100%" class="text-center">
<tr>
<td><img src="img/email_16.png" alt=""><em><a href="mailto:andreas.alex.vasilakis@gmail.com" target="_top"> andreas.alex.vasilakis[at]gmail.com</a></em></td>
</tr>
</table>
<hr>
<table style="width:100%" class="text-center">
<tr>
<td><img src="img/dblp_16.jpg" alt=""><a href="http://dblp.uni-trier.de/pers/hd/v/Vasilakis:Andreas"> DBLP </a></td>
<td><img src="img/linkedin_16.jpg" alt=""> <a href="https://www.linkedin.com/in/abasilak"> Linkedin</a></td>
<td><img src="img/scholar_16.png" alt=""><a href="https://scholar.google.com/citations?authuser=1&user=6l-6QjMAAAAJ"> Scholar </a></td>
<td><img src="img/pdf_16.png" alt=""><em><a href="resume/cv_vasilakis.pdf"> CV</a></em></td>
<td><img src="img/twitter_16.png" alt=""><em> <a href="https://twitter.com/abasilak"> abasilak</a></em></td>
<td><img src="img/skype_16.png" alt=""><em> abasilak</em></td>
<td><img src="img/github_16.png" alt=""><em> <a href="https://github.com/abasilak"> abasilak</a></em></td>
</tr>
</table>
<hr>
<h4 class="text-center">
<span class="label label-default"><a href="#info">Info</a></span>
<span class="label label-primary"><a href="#news">News</a></span>
<span class="label label-success"><a href="#publications">Publications</a></span>
<span class="label label-info"><a href="#education">Education</a></span>
<span class="label label-danger"><a href="#resources">Resources</a></span>
<span class="label label-warning"><a href="#source">Source Code</a></span>
<span class="label label-info"><a href="#meshes">Meshes</a></span>
</h4>
<p class="text-center"><em> *No triangles were harmed during the implementation of my research work.</em></p>
</div>
</div>
<div id="abstract" class="row">
<div id="info" class="col-sm-12 text-justify">
<hr>
<h3><span class="label label-default">Hi, welcome to my personal web-page</span></h3>
<p>
My name is Andreas-Alexandros Vasilakis and I was born on October 12, 1983, in <a href="https://en.wikipedia.org/wiki/Corfu"> Corfu, Greece</a>. I received my PhD on the field of Computer Graphics from the <a href="http://www.cs.uoi.gr">Department of Computer Science & Engineering</a> of the <a href="htttp://www.uoi.gr">University of Ioannina</a> in Greece, under the supervision of Prof. <a href="http://www.cs.uoi.gr/~fudos">Ioannis Fudos</a>. My <a href="#thesis.phd"> PhD studies</a> were supported by a scholarship from the <a href="http://irakleitos.uoi.gr/">Heraclitus II</a> grant through the operational programme "Education and Lifelong Learning" through the European Social Fund, 2010-2013. I have also received BSc and <a href="#thesis.master"> MSc</a> Degrees from the same institution in 2006 and 2008, respectively.
I am currently a postdoctoral fellow in Athens University of Economics and Business as well as adjunct lecturer in the Department of Computer Science and Engineering of Ioannina University. My research interests include interactive graphics, geometry processing techniques and rendering algorithms.
</p>
<p>
Recently, I cofounded <a href="https://www.phasmatic.com"> Phasmatic</a>, a company which pushes the boundaries of photorealistic 3D graphics on the web.
</p>
</div>
<div id="news" class="col-sm-12 text-justify">
<hr>
<h3>Latest News</h3>
<hr>
<div class="col-sm-7">
<h4><span class="label label-warning">Projects</span></h4>
<dl>
<dd> <span class="glyphicon glyphicon-calendar"></span> <strong>[10.22]</strong> VR cluster rendering, FHW </dd>
<dd> <span class="glyphicon glyphicon-calendar"></span> <strong>[03.22]</strong> VR/AR education content creation, FHW </dd>
<dd> <span class="glyphicon glyphicon-calendar"></span> <strong>[01.22]</strong> Virtual Sculpting, FHW </dd>
<dd> <span class="glyphicon glyphicon-calendar"></span> <strong>[01.21]</strong> <a href="https://www.rayground.com">Epic MegaGrants</a> funding for
<a href="https://www.rayground.com">Rayground</a>, Epic </dd>
<dd> <span class="glyphicon glyphicon-calendar"></span> <strong>[11.20]</strong> <a href="https://www.phasmatic.com">Phasmatic.com</a>, Photorealistic 3D Graphics on the Web</dd>
</dl>
<h4><span class="label label-success">Collaborations</span></h4>
<dl>
<dd> <span class="glyphicon glyphicon-calendar"></span> <strong>[10.22]</strong> Adjunct Professor,
C++ Programming, BSc in Informatics, <a href="http://www.cs.aueb.gr">AUEB</a>
</dd>
<dd> <span class="glyphicon glyphicon-calendar"></span> <strong>[06.22]</strong>
Program Committee, Technical Communications & Posters, <a href="https://sa2022.siggraph.org/en/">ACM SIGGRAPH Asia 2022</a>
</dd>
<dd> <span class="glyphicon glyphicon-calendar"></span> <strong>[04.22]</strong> Adjunct Professor,
Interaction Design & Multimedia, MSc in Digital Humanities, <a href="https://www.dept.aueb.gr/en/infotech-overview-en">AUEB</a>
</dd>
<dd> <span class="glyphicon glyphicon-calendar"></span> <strong>[02.22]</strong> Adjunct Professor,
VR/AR/MR, BSc in CS & Engineering, <a href="http://www.cs.uoi.gr">UOI</a>
</dd>
<dd> <span class="glyphicon glyphicon-calendar"></span> <strong>[10.21]</strong> Adjunct Professor,
Advanced Computer Graphics, BSc in CS & Engineering, <a href="http://www.cs.uoi.gr">UOI</a>
</dd>
</dl>
</div>
<div class="col-sm-5">
<h4><span class="label label-primary">Papers</span></h4>
<dl>
<dd> <span class="glyphicon glyphicon-calendar"></span> <strong>[06.22]</strong> Full Paper accepted @<a href="#vc2022">CGI2022</a> </dd>
<dd> <span class="glyphicon glyphicon-calendar"></span> <strong>[06.21]</strong> Full Paper accepted @<a href="#cga2021">CG&A2021</a> </dd>
<dd> <span class="glyphicon glyphicon-calendar"></span> <strong>[05.21]</strong> Best Poster Award @<a href="#eg2021">EG2021</a> </dd>
<dd> <span class="glyphicon glyphicon-calendar"></span> <strong>[03.21]</strong> Book Chapter accepted @<a href="#rtgii2021">RTGII</a> </dd>
<dd> <span class="glyphicon glyphicon-calendar"></span> <strong>[03.21]</strong> Poster accepted @<a href="#eg2021">EG2021</a> </dd>
<dd> <span class="glyphicon glyphicon-calendar"></span> <strong>[11.20]</strong> Full Paper accepted @<a href="#jcgt2021">JCGT2021</a> </dd>
</dl>
<h4><span class="label label-danger">Meetings</span></h4>
<dl>
<dd> <span class="glyphicon glyphicon-calendar"></span> <strong>[10.22]</strong> Researcher Night </dd>
<dd> <span class="glyphicon glyphicon-calendar"></span> <strong>[06.22]</strong> XR Cosmos, @FHW </dd>
<dd> <span class="glyphicon glyphicon-calendar"></span> <strong>[05.21]</strong> <a href="https://conferences.eg.org/eg2021/">Eurographics 2021</a>, Virtual </dd>
</dl>
</div>
</div>
</div>
<hr>
<div id="publications">
<h3>Publications (complete list)
<a href="resume/publications_list_vasilakis.pdf"> <img src="img/pdf_32.png" alt="publications list" title="publications list"> </a>
</h3>
<hr>
</div>
<div id="journals">
<h4><b>Journals/Book Chapters</b></h4>
<hr>
<div id="vc2022" class="row col-xs-12">
<div class="row text-center">
<div class="col-sm-7">
<h4>
<span class="label label-default">G. Tsopouridis</span>
<span class="label label-default">I. Fudos</span>
<span class="label label-danger">A. A. Vasilakis</span>
</h4>
<h4><span class="label label-info">Deep Hybrid Order-Independent Transparency</span></h4>
<h4>
<span class="label label-warning">multifragment rendering</span>
<span class="label label-warning">k-buffer</span>
<span class="label label-warning">order independent transparency</span>
<span class="label label-warning">deep learning</span>
</h4>
</div>
<div class="col-sm-5">
<h4><span class="label label-success">VC (CGI'22)</span></h4>
<h5><span class="glyphicon glyphicon-calendar" aria-hidden="true"></span>July 2022</h5>
<h4>
<a href="papers/journals/vc2022/paper.pdf"> <img src="img/pdf_32.png" alt="author-prepared version" title="author-prepared version"> </a>
<a href="papers/journals/vc2022/paper.ris"> <img src="img/bibtex_32.png" alt="bibtex" title="bibtex"> </a>
<a href="https://github.com/gtsopus/dhoit"> <img src="img/github_32.png" alt="github" width="30" height="30" title="github"> </a>
<a href="https://rdcu.be/cQO4O "> <img src="img/springer_32.png" alt="visual computer" title="visual computer link"> </a>
</h4> </div>
</div>
<div class="row">
<div class="col-sm-3"> <img src="papers/journals/vc2022/teaser.png" alt="..." class="shadow img-rounded center-block" title="teaser"> </div>
<div class="col-sm-9 text-justify">
<p> Correctly compositing transparent fragments is an important and long-standing open problem in real-time computer graphics.
Multifragment rendering is considered a key solution to providing high-quality order-independent transparency at interactive frame rates.
To achieve that, practical implementations severely constrain the overall memory budget by adopting bounded fragment configurations such as the k-buffer.
Relying on an iterative trial-and-error procedure, however, where the value of k is manually configured per case scenario, can inevitably result in bad
memory utilization and view-dependent artifacts. To this end, we introduce a novel intelligent k-buffer approach that performs a non-uniform per pixel
fragment allocation guided by a deep learning prediction mechanism. A hybrid scheme is further employed to facilitate the approximate blending of
non-significant (remaining) fragments and thus contribute to a better overall final color estimation. An experimental evaluation substantiates that our
method outperforms previous approaches when evaluating transparency in various high depth-complexity scenes.
</p>
</div>
<div class="col-xs-12">
<hr> </div>
</div>
</div>
<div id="rtgii2021" class="row col-xs-12">
<div class="row text-center">
<div class="col-sm-7">
<h4>
<span class="label label-default">N. Vitsas</span>
<span class="label label-default">A. Gkaravelis</span>
<span class="label label-danger">A. A. Vasilakis</span>
<span class="label label-default">G. Papaioannou</span>
</h4>
<h4><span class="label label-info">WebRays: Ray Tracing on the Web</span></h4>
<h4>
<span class="label label-warning">ray tracing</span>
<span class="label label-warning">WebGL</span>
<span class="label label-warning">API</span>
</h4> </div>
<div class="col-sm-5">
<h4><span class="label label-success">RTG II, ch. 18, pp. 281-299</span></h4>
<h5><span class="glyphicon glyphicon-calendar" aria-hidden="true"></span> August, 2021</h5>
<h4>
<a href="papers/journals/rtgii2021/paper.pdf"> <img src="img/pdf_32.png" alt="author-prepared version" title="author-prepared version"> </a>
<a href="papers/journals/rtgii2021/paper.bib"> <img src="img/bibtex_32.png" alt="bibtex" title="bibtex"> </a>
<a href="https://github.com/phasmatic3d/webrays"> <img src="img/github_32.png" alt="github" width="30" height="30" title="github"> </a>
<a href="https://cgaueb.github.io/publications/webrays/"> <img src="img/demo_32.png" alt="demo" title="demo"> </a>
<a href="https://link.springer.com/chapter/10.1007%2F978-1-4842-7185-8_18"> <img src="img/springer_32.png" alt="visual computer" title="visual computer link"> </a>
</h4>
</div>
</div>
<div class="row">
<div class="col-sm-3"> <img src="papers/journals/rtgii2021/teaser.jpg" alt="..." class="shadow img-rounded center-block" title="rtgii2021 teaser"> </div>
<div class="col-sm-9 text-justify">
<p>
This chapter introduces us to a new API built for doing ray tracing in a web browser, expanding hardware accelerated ray tracing access to web applications.
WebRays is currently powering the web site Rayground, which allows people to both develop and run ray tracing applications in their web browser.
WebRays support shaders written in glsl via WebGL, and provides a JavaScript host-side API, and glsl device-side API to enable hardware accelerated ray-triangle intersections.
This ray-casting API has been designed to allow both wavefront and megakernel style architectures, and tries to make room for any style of ray tracing pipeline the user wants.
<br>
</p>
</div>
<div class="col-xs-12">
<hr> </div>
</div>
</div>
<div id="cga2021" class="row col-xs-12">
<div class="row text-center">
<div class="col-sm-7">
<h4>
<span class="label label-danger">A. A. Vasilakis</span>
<span class="label label-default">G. Papaioannou</span>
<span class="label label-default">N. Vitsas</span>
<span class="label label-default">A. Gkaravelis</span>
</h4>
<h4><span class="label label-info">Remote Teaching Advanced Rendering Topics using the Rayground Platform</span></h4>
<h4>
<span class="label label-warning">remote teaching</span>
<span class="label label-warning">computer graphics course</span>
<span class="label label-warning">prototyping</span>
<span class="label label-warning">ray tracing</span>
</h4> </div>
<div class="col-sm-5">
<h4><span class="label label-success">IEEE CG&A, vol. 41, issue 5, pp. 99-103</span></h4>
<h5><span class="glyphicon glyphicon-calendar" aria-hidden="true"></span> September, 2021</h5>
<h4>
<a href="papers/journals/cga2021/paper.pdf"> <img src="img/pdf_32.png" alt="author-prepared version" title="author-prepared version"> </a>
<a href="papers/journals/cga2021/paper.bib"> <img src="img/bibtex_32.png" alt="bibtex" title="bibtex"> </a>
<a href="https://www.rayground.com"> <img src="img/rg.png" alt="rg" width="40" height="20" title="rayground site"> </a>
<a href="https://github.com/cgaueb/rayground"> <img src="img/github_32.png" alt="github" width="30" height="30" title="github"> </a>
<a href="https://doi.ieeecomputersociety.org/10.1109/MCG.2021.3093734"> <img src="img/ieee_32.jpg" alt="ieee" title="ieee link"> </a>
</h4>
</div>
</div>
<div class="row">
<div class="col-sm-3"> <img src="papers/journals/cga2021/teaser.jpg" alt="..." class="shadow img-rounded center-block" title="cga2021 teaser"> </div>
<div class="col-sm-9 text-justify">
<p>
Rayground is a novel online framework for fast prototyping and interactive demonstration of ray tracing algorithms. It aims to set the ground for the online development of
ray-traced visualization algorithms in an accessible manner for everyone, stripping off the mechanics that get in the way of creativity and the understanding of the core concepts.
Due to the COVID-19 pandemic, remote teaching and online coursework have taken center stage. In this work, we demonstrate how Rayground can incorporate advanced instructive rendering media
during online lectures as well as offer attractive student assignments in an engaging, hands-on manner. We cover things to consider when building or porting methods to this new development
platform, best practices in remote teaching and learning activities and time-tested assessment and grading strategies suitable for fully online university courses.
<br>
</p>
</div>
<div class="col-xs-12">
<hr> </div>
</div>
</div>
<div id="jcgt2021" class="row col-xs-12">
<div class="row text-center">
<div class="col-sm-7">
<h4>
<span class="label label-default">I. Evangelou</span>
<span class="label label-default">G. Papaioannou</span>
<span class="label label-default">K. Vardis</span>
<span class="label label-danger">A. A. Vasilakis</span>
</h4>
<h4><span class="label label-info">Fast Radius Search Exploiting Ray Tracing Frameworks</span></h4>
<h4>
<span class="label label-warning">ray tracing</span>
<span class="label label-warning">photon mapping</span>
<span class="label label-warning">point cloud registration</span>
<span class="label label-warning">k-nearest neighbors</span>
</h4>
</div>
<div class="col-sm-5">
<h4><span class="label label-success">JCGT, vol. 10, no. 1, pp. 25-48</span></h4>
<h5><span class="glyphicon glyphicon-calendar" aria-hidden="true"></span>February 2021</h5>
<h4>
<a href="papers/journals/jcgt2021/paper.pdf"> <img src="img/pdf_32.png" alt="author-prepared version" title="author-prepared version"> </a>
<a href="http://www.jcgt.org/published/0010/01/02/"> <img src="img/jcgt_32.png" alt="jcgt" title="jcgt link"> </a>
<a href="papers/journals/jcgt2021/paper.bib"> <img src="img/bibtex_32.png" alt="bibtex" title="bibtex"> </a>
<a href="https://github.com/cgaueb/fast_radius_search"> <img src="img/github_32.png" alt="github" width="30" height="30" title="github"> </a>
</h4> </div>
</div>
<div class="row">
<div class="col-sm-3"> <img src="papers/journals/jcgt2021/teaser.png" alt="..." class="shadow img-rounded center-block" title="jcgt2021 teaser"> </div>
<div class="col-sm-9 text-justify">
<p> Spatial queries to infer information from the neighborhood of a set of points are very frequently performed in rendering and geometry processing algorithms.
Traditionally, these are accomplished using radius and k-nearest neighbors search operations, which utilize kd-trees and other specialized spatial data structures that fall short of delivering high performance.
Recently, advances in ray tracing performance, with respect to both acceleration data structure construction and ray traversal times, have resulted in a wide adoption of the ray tracing paradigm for graphics-related
tasks that spread beyond typical image synthesis. In this work, we propose an alternative formulation of the radius search operation that maps the problem to the ray tracing paradigm, in order to take advantage of the
available GPU-accelerated solutions for it. We demonstrate the performance gain relative to traditional spatial search methods, especially on dynamically updated sample sets, using two representative applications:
geometry processing point-wise operations on scanned point clouds and global illumination via progressive photon mapping.
</p>
</div>
<div class="col-xs-12">
<hr> </div>
</div>
</div>
<div id="vc2020" class="row col-xs-12">
<div class="row text-center">
<div class="col-sm-7">
<h4>
<span class="label label-default">I. Evangelou</span>
<span class="label label-default">G. Papaioannou</span>
<span class="label label-default">K. Vardis</span>
<span class="label label-danger">A. A. Vasilakis</span>
</h4>
<h4><span class="label label-info">Rasterization-based Progressive Photon Mapping</span></h4>
<h4>
<span class="label label-warning">photon mapping</span>
<span class="label label-warning">rasterization</span>
<span class="label label-warning">ray tracing</span>
</h4>
</div>
<div class="col-sm-5">
<h4><span class="label label-success">VC (CGI'20), vol. 36 , no. 10, pp. 1993-2004</span></h4>
<h5><span class="glyphicon glyphicon-calendar" aria-hidden="true"></span>July 2020</h5>
<h4>
<a href="papers/journals/vc2020/paper.pdf"> <img src="img/pdf_32.png" alt="author-prepared version" title="author-prepared version"> </a>
<a href="papers/journals/vc2020/paper.bib"> <img src="img/bibtex_32.png" alt="bibtex" title="bibtex"> </a>
<a href="https://github.com/cgaueb/MFR/blob/master/Multimedia/CGI2020_presentation.pptx"> <img src="img/ppt_32.jpg" alt="presentation" title="presentation"> </a>
<a href="https://youtu.be/csEpdbZjTfY"> <img src="img/youtube_26.png" alt="video" title="youtube video"> </a>
<a href="https://link.springer.com/article/10.1007%2Fs00371-020-01897-3"> <img src="img/springer_32.png" alt="visual computer" title="visual computer link"> </a>
</h4> </div>
</div>
<div class="row">
<div class="col-sm-3"> <img src="papers/journals/vc2020/teaser.png" alt="..." class="shadow img-rounded center-block" title="eg2020star teaser"> </div>
<div class="col-sm-9 text-justify">
<p> Ray tracing on the GPU has been synergistically operating alongside rasterization in interactive rendering engines for some time now, in order to
accurately capture certain illumination effects. In the same spirit, in this paper, we propose an implementation of Progressive Photon Mapping entirely on the
rasterization pipeline, which is agnostic to the specific GPU architecture, in order to synthesise images at interactive rates. While any GPU ray tracing architecture
can be used for photon mapping, performing ray traversal in image space minimises acceleration data structure construction time and supports arbitrarily complex
and fully dynamic geometry. Furthermore, this strategy maximises data structure reuse by encompassing rasterization, ray tracing and photon gathering tasks in a
single data structure. Both eye and light paths of arbitrary depth are traced on multi-view deep G-buffers and photon flux is gathered by a properly adapted multi-view
photon splatting. In contrast to previous methods exploiting rasterization to some extent, due to our novel indirect photon splatting approach, any event combination
present in photon mapping is captured. We evaluate our method using typical test scenes and scenarios for photon mapping methods and show how our approach outperforms
typical GPU-based progressive photon mapping.
</p>
</div>
<div class="col-xs-12">
<hr> </div>
</div>
</div>
<div id="cgf2020star" class="row col-xs-12">
<div class="row text-center">
<div class="col-sm-7">
<h4>
<span class="label label-danger">A. A. Vasilakis✝</span>
<span class="label label-default">K. Vardis✝</span>
<span class="label label-default">G. Papaioannou</span>
</h4>
<h4><span class="label label-info">A Survey of Multifragment Rendering</span></h4>
<h4>
<span class="label label-warning">rasterization</span>
<span class="label label-warning">interactive rendering</span>
<span class="label label-warning">visibility determination</span>
</h4>
</div>
<div class="col-sm-5">
<h4><span class="label label-success">CGF (EG'20), vol. 39 , no. 2, pp. 623-642</span></h4>
<h5><span class="glyphicon glyphicon-calendar" aria-hidden="true"></span>May 2020</h5>
<h4>
<a href="papers/journals/eg2020star/paper.pdf"> <img src="img/pdf_32.png" alt="author-prepared version" title="author-prepared version"> </a>
<a href="papers/journals/eg2020star/presentation.pptx"> <img src="img/ppt_32.jpg" alt="presentation" title="presentation"> </a>
<a href="papers/journals/eg2020star/paper.bib"> <img src="img/bibtex_32.png" alt="bibtex" title="bibtex"> </a>
<a href="https://youtu.be/bxX8BVxfbYA"> <img src="img/youtube_26.png" alt="video" title="youtube video"> </a>
<a href="https://github.com/cgaueb/MFR"> <img src="img/github_32.png" alt="github" width="30" height="30" title="github"> </a>
<a href="https://diglib.eg.org/handle/10.1111/cgf14019"> <img src="img/eg.png" alt="cgf" width="31" height="20" title="cgf link"> </a>
</h4> </div>
</div>
<div class="row">
<div class="col-sm-3"> <img src="papers/journals/eg2020star/teaser.png" alt="..." class="shadow img-rounded center-block" title="vc2020star teaser"> </div>
<div class="col-sm-9 text-justify">
<p>
In the past few years, advances in graphics hardware have fuelled an explosion of research and development in the field of interactive and real-time rendering in screen space.
Following this trend, a rapidly increasing number of applications rely on multifragment rendering
solutions to develop visually convincing graphics applications with dynamic content.
The main advantage of these approaches is that they encompass additional rasterised geometry, by
retaining more information from the fragment sampling domain,
thus augmenting the visibility determination stage.
With this survey, we provide an overview of and insight into the extensive, yet active research and respective literature on multifragment rendering.
We formally present the multifragment rendering pipeline, clearly identifying the construction strategies, the core image operation categories and
their mapping to the respective applications. We describe features and trade-offs for each class of techniques, pointing out GPU optimisations and
limitations and provide practical recommendations for choosing an appropriate method for each application.
Finally, we offer fruitful context for discussion by outlining some existing problems and challenges as well as by presenting opportunities for impactful future research directions.
</p>
<br> ✝ <em>These authors contributed equally to this work.</em>
</div>
<div class="col-xs-12">
<hr> </div>
</div>
</div>
<div id="cgf2020fp" class="row col-xs-12">
<div class="row text-center">
<div class="col-sm-7">
<h4><span class="label label-default">N. Vitsas</span> <span class="label label-default">G. Papaioannou</span>
<span class="label label-default">A. Gkaravelis</span> <span class="label label-danger">A. A. Vasilakis</span>
</h4>
<h4><span class="label label-info">Illumination-Guided Furniture Layout Optimization</span></h4>
<h4>
<span class="label label-warning">inverse geometry</span>
<span class="label label-warning">layout optimization </span>
</h4>
</div>
<div class="col-sm-5">
<h4><span class="label label-success">CGF (EG'20), vol. 39, no. 2, pp. 291-301</span></h4>
<h5><span class="glyphicon glyphicon-calendar" aria-hidden="true"></span>May 2020</h5>
<h4>
<a href="papers/journals/eg2020fp/paper.pdf"> <img src="img/pdf_32.png" alt="author-prepared version" title="author-prepared version"> </a>
<a href="papers/journals/eg2020fp/paper.bib"> <img src="img/bibtex_32.png" alt="bibtex" title="bibtex"> </a>
<a href="https://youtu.be/d8yRxoVStXs"> <img src="img/youtube_26.png" alt="video" title="youtube video"> </a>
<a href="https://youtu.be/duNoZt7MFnc"> <img src="img/youtube_26.png" alt="FF video" title="youtube FF video"> </a>
<a href="https://diglib.eg.org/handle/10.1111/cgf13930"> <img src="img/eg.png" alt="cgf" width="31" height="20" title="cgf link"> </a>
</h4> </div>
</div>
<div class="row">
<div class="col-sm-3"> <img src="papers/journals/eg2020fp/teaser.png" alt="..." class="shadow img-rounded center-block" title="eg2020fp teaser"> </div>
<div class="col-sm-9 text-justify">
<p>
Lighting plays a very important role in interior design.
However, in the specific problem of furniture layout recommendation,
illumination has been either neglected or addressed with empirical or very simplified solutions.
The effectiveness of a particular layout in its expected task performance can be greatly affected by daylighting
and artificial illumination in a non-trivial manner. In this paper, we introduce a robust method for furniture
layout optimization guided by illumination constraints. The method takes into account all dominant light sources,
such as sun light, skylighting and fixtures, while also being able to handle movable light emitters.
For this task, the method introduces multiple generic illumination constraints and physically-based light transport estimators,
operating alongside typical geometric design guidelines, in a unified manner.
We demonstrate how to produce furniture arrangements that comply with important safety, comfort and efficiency illumination criteria,
such as glare suppression, under complex light-environment interactions, which are very hard to handle using empirical or simplified models.
</p>
</div>
<div class="col-xs-12">
<hr> </div>
</div>
</div>
<div id="vc2017" class="row col-xs-12">
<div class="row text-center">
<div class="col-sm-7">
<h4><span class="label label-default">A. Lalos</span> <span class="label label-danger">A. A. Vasilakis</span> <span class="label label-default">A. Dimas</span>
<span class="label label-default">K. Moustakas</span>
</h4>
<h4><span class="label label-info">Adaptive Compression of Animated Meshes by Exploiting Orthogonal Iterations</span></h4>
<h4>
<span class="label label-warning">animation</span>
<span class="label label-warning">compression</span>
<span class="label label-warning">subspace tracking</span>
<span class="label label-warning">orthogonal iterations</span>
</h4>
</div>
<div class="col-sm-5">
<h4><span class="label label-success">Visual Computer (CGI'17), vol. 33, no. 6, pp. 811-821</span></h4>
<h5><span class="glyphicon glyphicon-calendar" aria-hidden="true"></span>Jun 2017</h5>
<h4>
<a href="papers/journals/vc2017/paper.pdf"> <img src="img/pdf_32.png" alt="author-prepared version" title="author-prepared version"> </a>
<a href="papers/journals/vc2017/presentation.pdf"> <img src="img/ppt_32.jpg" alt="presentation" title="presentation"> </a>
<a href="papers/journals/vc2017/paper.bib"> <img src="img/bibtex_32.png" alt="bibtex" title="bibtex"> </a>
<a href="https://www.dropbox.com/s/dfg6g4e851bxhpo/2017%20-%20Adaptive%20Compression%20of%20Animated%20Meshes%20by%20Exploiting%20Orthogonal%20Iterations.mp4?dl=0"> <img src="img/video_26.png" alt="video" title="download video"> </a>
<a href="https://link.springer.com/article/10.1007%2Fs00371-017-1395-4"> <img src="img/springer_32.png" alt="visual computer" title="visual computer link"> </a>
</h4> </div>
</div>
<div class="row">
<div class="col-sm-3"> <img src="papers/journals/vc2017/teaser.png" alt="..." class="shadow img-rounded center-block" title="vc2017 teaser"> </div>
<div class="col-sm-9 text-justify">
<p>
We introduce a novel approach to support fast and efficient lossy compression of arbitrary animation sequences ideally suited for real-time scenarios, such as streaming and content creation applications, where input is not known a-priori and is dynamically generated. The presented method exploits temporal coherence by altering the principal component analysis (PCA) procedure from a batch- to an adaptive-basis aiming to simultaneously support three important, generally conflicting in prior art, objectives: fast compression times, reduced memory requirements and high quality reproduction results. To that end, we show how the problem of tracking subspaces via adaptive orthogonal iterations can be successfully applied to support bandwidth- as well as error-consistent encoding of sequentially processed animated data. A dynamic compression pipeline is presented that can efficiently approximate the k-largest PCA bases based on the previous iteration (frame block) at a significantly lower complexity than directly computing the singular value decomposition. To avoid under-fitting when a fixed number of basis vectors is used for all frame blocks, a flexible solution that automatically identifies the optimal subspace size for each one is also offered. An extensive experimental study is finally offered showing that our method is superior in terms of performance as compared to several direct PCA-based schemes while, at the same time, achieves plausible reconstruction output despite the constraints posed by arbitrarily complex animated scenarios.
</p>
</div>
<div class="col-xs-12">
<hr> </div>
</div>
</div>
<div id="tvcg2015" class="row col-xs-12">
<div class="row text-center">
<div class="col-sm-7">
<h4><span class="label label-danger">A. A. Vasilakis</span> <span class="label label-default">G. Papaioannou</span> <span class="label label-default">I. Fudos</span> </h4>
<h4><span class="label label-info">k+-buffer: An Efficient, Memory-Friendly and Dynamic k-buffer Framework</span></h4>
<h4>
<span class="label label-warning">depth peeling</span>
<span class="label label-warning">k-buffer</span>
<span class="label label-warning">A-buffer</span>
<span class="label label-warning">pixel sync</span>
<span class="label label-warning">depth complexity histogram</span>
<span class="label label-warning">animation</span>
</h4> </div>
<div class="col-sm-5">
<h4><span class="label label-success">TVCG, vol. 21, no. 6, pp. 688-700</span></h4>
<h5><span class="glyphicon glyphicon-calendar" aria-hidden="true"></span>Jun 2015</h5>
<h4>
<a href="papers/journals/tvcg2015/paper.pdf"> <img src="img/pdf_32.png" alt="author-prepared version" title="author-prepared version"> </a>
<a href="papers/journals/tvcg2015/shaders.zip"> <img src="img/source_32.png" alt="shader source code" title="shader source code"> </a>
<a href="papers/journals/tvcg2015/paper.bib"> <img src="img/bibtex_32.png" alt="bibtex" title="bibtex"> </a>
<a href="http://doi.ieeecomputersociety.org/10.1109/TVCG.2015.2417581"> <img src="img/ieee_32.jpg" alt="ieee" title="ieee link"> </a>
</h4> </div>
</div>
<div class="row">
<div class="col-sm-3"> <img src="papers/journals/tvcg2015/teaser.png" alt="..." class="shadow img-rounded center-block" title="tvcg2015 teaser"> </div>
<div class="col-sm-9 text-justify">
<p> Depth-sorted fragment determination is fundamental for a host of image-based techniques which simulates complex rendering effects. It is also a challenging task in terms of time and space required when rasterizing scenes with high depth complexity. When low graphics memory requirements are of utmost importance, k-buffer can objectively be considered as the most preferred framework which advantageously ensures the correct depth order on a subset of all generated fragments. Although various alternatives have been introduced to partially or completely alleviate the noticeable quality artifacts produced by the initial k-buffer algorithm in the expense of memory increase or performance downgrade, appropriate tools to automatically and dynamically compute the most suitable value of k are still missing. To this end, we introduce k+-buffer, a fast framework that accurately simulates the behavior of k-buffer in a single rendering pass. Two memory-bounded data structures: (i) the max-array and (ii) the max-heap are developed on the GPU to concurrently maintain the k-foremost fragments per pixel by exploring pixel synchronization and fragment culling. Memory-friendly strategies are further introduced to dynamically (a) lessen the wasteful memory allocation of individual pixels with low depth complexity frequencies, (b) minimize the allocated size of k-buffer according to different application goals and hardware limitations via a straightforward depth histogram analysis and (c) manage local GPU cache with a fixed-memory depth-sorting mechanism. Finally, an extensive experimental evaluation is provided demonstrating the advantages of our work over all prior k-buffer variants in terms of memory usage, performance cost and image quality. </p>
</div>
<div class="col-xs-12">
<hr> </div>
</div>
</div>
<div id="cgf2014" class="row col-xs-12">
<div class="row text-center">
<div class="col-sm-7">
<h4><span class="label label-danger">A. A. Vasilakis</span> <span class="label label-default">I. Fudos</span> </h4>
<h4><span class="label label-info">Pose Partitioning for Multi-resolution Segmentation of Arbitrary Mesh Animations</span>
</h4>
<h4>
<span class="label label-warning">multi-resolution</span>
<span class="label label-warning">variable</span>
<span class="label label-warning">global</span>
<span class="label label-warning">segmentation</span>
<span class="label label-warning">skinning</span>
<span class="label label-warning">animation</span>
</h4> </div>
<div class="col-sm-5">
<h4><span class="label label-success">CGF (EG'14), vol. 33, no. 2, pp. 293-302</span></h4>
<h5><span class="glyphicon glyphicon-calendar" aria-hidden="true"></span>Strasbourg, France, April 2014</h5>
<h4>
<a href="papers/journals/cgf2014/paper.pdf"> <img src="img/pdf_32.png" alt="author-prepared version" title="author-prepared version"> </a>
<a href="papers/journals/cgf2014/presentation.pptx"> <img src="img/ppt_32.jpg" alt="presentation" title="presentation"> </a>
<a href="papers/journals/cgf2014/presentation_ff.pptx"> <img src="img/ppt_32.jpg" alt="FF presentation" title="FF presentation"> </a>
<a href="papers/journals/cgf2014/paper.bib"> <img src="img/bibtex_32.png" alt="bibtex" title="bibtex"> </a>
<a href="http://www.cgrg.cs.uoi.gr/wp-content/uploads/bezier/publications/vasilakis-fudos-eg2014/video.mp4"> <img src="img/video_26.png" alt="video" title="download video"> </a>
<a href="https://www.youtube.com/watch?v=uBE6pDV1e5A"> <img src="img/youtube_26.png" alt="video" title="youtube video"> </a>
<a href="http://onlinelibrary.wiley.com/doi/10.1111/cgf.12327/abstract"> <img src="img/eg.png" alt="cgf" width="31" height="20" title="cgf link"> </a>
</h4> </div>
</div>
<div class="row">
<div class="col-sm-3"> <img src="papers/journals/cgf2014/teaser.png" alt="..." class="shadow img-rounded center-block" title="cgf2014 teaser"> </div>
<div class="col-sm-9 text-justify"> We present a complete approach to efficiently deriving a varying level-of-detail segmentation of arbitrary animated objects. An over-segmentation is built by combining sets of initial segments computed for each input pose, followed by a fast progressive simplification which aims at preserving rigid segments. The final segmentation result can be efficiently adjusted for cases where pose editing is performed or new poses are added at arbitrary positions in the mesh animation sequence. A smooth view of pose-to-pose segmentation transitions is offered by merging the partitioning of the current pose with that of the next pose. A perceptually friendly visualization scheme is also introduced for propagating segment colors between consecutive poses.We report on the efficiency and quality of our framework as compared to previous methods under a variety of skeletal and highly deformable mesh animations. </div>
</div>
<div class="col-xs-12">
<hr> </div>
</div>
<div id="tvcg2013" class="row col-xs-12">
<div class="row text-center">
<div class="col-sm-7">
<h4><span class="label label-danger">A. A. Vasilakis</span> <span class="label label-default">I. Fudos</span> </h4>
<h4><span class="label label-info">Depth-fighting Aware Methods for Multifragment Rendering</span></h4>
<h4>
<span class="label label-warning">A-buffer</span>
<span class="label label-warning">z-fighting</span>
<span class="label label-warning">depth peeling</span>
<span class="label label-warning">visibility ordering</span>
<span class="label label-warning">multifragment rendering</span>
</h4> </div>
<div class="col-sm-5">
<h4><span class="label label-success">TVCG (I3D'13), vol. 19, no. 6, pp. 967-977</span></h4>
<h5><span class="glyphicon glyphicon-calendar" aria-hidden="true"></span> Orlando, FL, USA, Mar 2013</h5>
<h4>
<a href="papers/journals/tvcg2013/paper.pdf"> <img src="img/pdf_32.png" alt="author-prepared version" title="author-prepared version"> </a>
<a href="papers/journals/tvcg2013/presentation_i3d.ppsx"> <img src="img/ppt_32.jpg" alt="presentation" title="presentation"> </a>
<a href="papers/journals/tvcg2013/shaders.tar"> <img src="img/source_32.png" alt="shader source code" title="shader source code"> </a>
<a href="papers/journals/tvcg2013/paper.bib"> <img src="img/bibtex_32.png" alt="bibtex" title="bibtex"> </a>
<a href="https://youtu.be/NB2AevIrbhQ"> <img src="img/youtube_26.png" alt="video" title="youtube video"> </a>
<a href="http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6331487"> <img src="img/ieee_32.jpg" alt="ieee" title="ieee link"> </a>
</h4> </div>
</div>
<div class="row">
<div class="col-sm-3"> <img src="papers/journals/tvcg2013/teaser.png" alt="tvcg2013 teaser" class="shadow img-rounded center-block" title="tvcg2013 teaser"> </div>
<div class="col-sm-9 text-justify">
<p> Many applications require operations on multiple fragments that result from ray casting at the same pixel location. To this end, several approaches have been introduced that process for each pixel one or more fragments per rendering pass, so as to produce a multifragment effect. However, multifragment rasterization is susceptible to flickering artifacts when two or more visible fragments of the scene have identical depth values. This phenomenon is called coplanarity or Z-fighting and incurs various unpleasant and unintuitive results when rendering complex multilayer scenes. In this work, we develop depth-fighting aware algorithms for reducing, eliminating and/or detecting related flaws in scenes suffering from duplicate geometry. We adapt previously presented single and multipass rendering methods, providing alternatives for both commodity and modern graphics hardware. We report on the efficiency and robustness of all these alternatives and provide comprehensive comparison results. Finally, visual results are offered illustrating the effectiveness of our variants for a number of applications where depth accuracy and order are of critical importance. </p>
</div>
<div class="col-xs-12">
<hr> </div>
</div>
</div>
<div id="cad2013" class="row col-xs-12">
<div class="row text-center">
<div class="col-sm-7">
<h4> <span class="label label-default">J. Rossignac</span> <span class="label label-default">I. Fudos</span> <span class="label label-danger">A. A. Vasilakis</span>
</h4>
<h4><span class="label label-info">Direct Rendering of Boolean Combinations of Self-Trimmed Surfaces</span>
</h4>
<h4>
<span class="label label-warning">classification rules</span>
<span class="label label-warning">trimming</span>
<span class="label label-warning">capping</span>
<span class="label label-warning">clipping</span>
<span class="label label-warning">CSG</span>
<span class="label label-warning">multifragment rendering</span>
</h4> </div>
<div class="col-sm-5">
<h4><span class="label label-success">CAD (SPM'12), vol. 45, no. 2, pp. 288-300</span>
</h4>
<h5><span class="glyphicon glyphicon-calendar" aria-hidden="true"></span> Dijon, France, Oct 2012</h5>
<h4>
<a href="papers/journals/cad2013/paper.pdf"> <img src="img/pdf_32.png" alt="author-prepared version" title="author-prepared version"> </a>
<a href="papers/journals/cad2013/presentation.ppt"> <img src="img/ppt_32.jpg" alt="presentation" title="presentation"> </a>
<a href="papers/journals/cad2013/shaders.zip"> <img src="img/source_32.png" alt="shader source code" title="shader source code"> </a>
<a href="papers/journals/cad2013/paper.bib"> <img src="img/bibtex_32.png" alt="bibtex" title="bibtex"> </a>
<a href="http://www.cgrg.cs.uoi.gr/wp-content/uploads/bezier/publications/trimming/trimming-videos.zip"> <img src="img/video_26.png" alt="video" title="download video"> </a>
<a href="https://youtu.be/InTUU7MRKcM"> <img src="img/youtube_26.png" alt="video" title="youtube video 1"> </a>
<a href="https://youtu.be/r6Yi6wR4b0Q"> <img src="img/youtube_26.png" alt="video" title="youtube video 2"> </a>
<a href="http://www.sciencedirect.com/science/article/pii/S0010448512002175"> <img src="img/elsevier.png" alt="cad" width="26" height="30" title="cad link"> </a>
</h4> </div>
</div>
<div class="row">
<div class="col-sm-3"> <img src="papers/journals/cad2013/teaser.png" alt="cad2013 teaser" class="shadow img-rounded center-block" title="cad2013 teaser"> </div>
<div class="col-sm-9 text-justify">
<p> We explore different semantics for the solid defined by a self-crossing surface (immersed sub-manifold). Specifically, we introduce rules for the interior/exterior classification of the connected components of the complement of a self-crossing surface produced through a continuous deformation process of an initial embedded manifold. We propose efficient GPU algorithms for rendering the boundary of the regularized union of the interior components, which is a subset of the initial surface and is called the trimmed boundary or simply the trim. This classification and rendering process is accomplished in realtime through a rasterization process without computing any self-intersection curve, and hence is suited to support animations of self-crossing surfaces. The solid bounded by the trim can be combined with other solids and with half-spaces using Boolean operations and hence may be capped (trimmed by a half-space) or used as a primitive in direct CSG rendering. Being able to render the trim in realtime makes it possible to adapt the tessellation of the trim in realtime by using view-dependent levels-of-details or adaptive subdivision. </p>
</div>
<div class="col-xs-12">
<hr> </div>
</div>
</div>
<div id="cavw2011" class="row col-xs-12">
<div class="row text-center">
<div class="col-sm-7">
<h4><span class="label label-danger">A. A. Vasilakis</span> <span class="label label-default">I. Fudos</span> </h4>
<h4><span class="label label-info">GPU rigid skinning based on a refined skeletonization method</span></h4>
<h4>
<span class="label label-warning">skeletonization</span>
<span class="label label-warning">skinning</span>
<span class="label label-warning">re-meshing</span>
<span class="label label-warning">GPU</span>
<span class="label label-warning">character</span>
<span class="label label-warning">animation</span>
</h4> </div>
<div class="col-sm-5">
<h4><span class="label label-success">CAVW, vol. 22, no. 1, pp. 27-46</span></h4>
<h5><span class="glyphicon glyphicon-calendar" aria-hidden="true"></span> Jan 2011</h5>
<h4>
<a href="papers/journals/cavw2011/paper.pdf"> <img src="img/pdf_32.png" alt="author-prepared version" title="author-prepared version"> </a>
<a href="papers/journals/cavw2011/paper.bib"> <img src="img/bibtex_32.png" alt="bibtex" title="bibtex"> </a>
<a href="http://onlinelibrary.wiley.com/doi/10.1002/cav.382/abstract"> <img src="img/cavw.png" alt="cavw" width="75" height="26" title="cavw link"> </a>
</h4> </div>
</div>
<div class="row">
<div class="col-sm-3"> <img src="papers/journals/cavw2011/teaser.png" alt="cavw2011 teaser" class="shadow img-rounded center-block" title="cavw2011 teaser"> </div>
<div class="col-sm-9 text-justify">
<p> In this paper, we present a skeletal rigid skinning approach. First, we describe a skeleton extraction technique that produces refined skeletons appropriate for animation from decomposed character models. Then, to avoid the artifacts generated in previous skinning approaches and the associated high training costs, we develop an efficient and robust rigid skinning technique that applies blending patches around joints. To achieve real time animation, we have adapted all steps of our rigid skinning algorithm so that they are performed efficiently on the GPU. Finally, we present an evaluation of our methods against four criteria: efficiency, quality, scope, and robustness. </p>
</div>
<div class="col-xs-12">
<hr> </div>
</div>
</div>
</div>
<div id="conferences">
<h4><b>Conferences (Papers: Full, Short, Posters)</b></h4>
<hr>
<div id="eg2021" class="row col-xs-12">
<div class="row text-center">
<div class="col-sm-7">
<h4>
<span class="label label-default">K. Vardis✝</span>
<span class="label label-danger">A. A. Vasilakis✝</span>
<span class="label label-default">G. Papaioannou</span>
</h4>
<h4><span class="label label-info">Illumination-driven Light Probe Placement</span>
<a href="https://pbs.twimg.com/media/E0zAwwaWYAAhlgn?format=jpg&name=medium">★</a>
</h4>
<h4>
<span class="label label-warning">light probes</span>
<span class="label label-warning">interactive rendering</span>
<span class="label label-warning">simplification </span>
</h4>
</div>
<div class="col-sm-5">
<h4><span class="label label-success">EG (Posters), 2021, pp. 1-1</span></h4>
<h5><span class="glyphicon glyphicon-calendar" aria-hidden="true"></span>Vienna, Austria, May 2021</h5>
<h4>
<a href="papers/conferences/eg2021/paper.pdf"> <img src="img/pdf_32.png" alt="author-prepared version" title="author-prepared version"> </a>
<a href="papers/conferences/eg2021/poster.pdf"> <img src="img/ppt_32.jpg" alt="presentation" title="presentation"> </a>
<a href="papers/conferences/eg2021/paper.bib"> <img src="img/bibtex_32.png" alt="bibtex" title="bibtex"> </a>
<a href="https://youtu.be/n3ACAjlhgJQ"> <img src="img/youtube_26.png" alt="video" title="youtube video"> </a>
<a href="https://github.com/cgaueb/light_probe_placement"> <img src="img/github_32.png" alt="github" width="30" height="30" title="github"> </a>
<a href="https://diglib.eg.org/handle/10.2312/egp20211026"> <img src="img/eg.png" alt="cgf" width="31" height="20" title="cgf link"> </a>
</h4> </div>
</div>
<div class="row">
<div class="col-sm-3"> <img src="papers/conferences/eg2021/teaser.png" alt="..." class="shadow img-rounded center-block" title="eg2021 teaser"> </div>
<div class="col-sm-9 text-justify">
<p>
We introduce a simplification method for light probe configurations that preserves the indirect illumination distribution in
scenes with diverse lighting conditions. An iterative graph simplification algorithm discards the probes that, according to a set
of evaluation points, have the least impact on the global light field. Our approach is simple, generic and aims at improving the
repetitive and often non-intuitive and tedious task of placing light probes on complex virtual environments.
</p>
<br> ✝ <em>These authors contributed equally to this work.</em>
</div>
<div class="col-xs-12">
<hr> </div>
</div>
</div>
<div id="eg2020edu" class="row col-xs-12">
<div class="row text-center">
<div class="col-sm-7">
<h4>
<span class="label label-default">N. Vitsas</span>
<span class="label label-default">A. Gkaravelis</span>
<span class="label label-danger">A. A. Vasilakis</span>
<span class="label label-default">K. Vardis</span>
<span class="label label-default">G. Papaioannou</span>
</h4>
<h4><span class="label label-info">Rayground: An Online Educational Tool for Ray Tracing</span></h4>
<h4>
<span class="label label-warning">prototyping</span>
<span class="label label-warning">ray tracing</span>
<span class="label label-warning">teaching</span>
<span class="label label-warning">WebGL</span>
</h4> </div>
<div class="col-sm-5">
<h4><span class="label label-success">EG (Education), 2020, pp. 01-08</span></h4>
<h5><span class="glyphicon glyphicon-calendar" aria-hidden="true"></span> Norrköping, Sweden, May 2020</h5>
<h4>
<a href="https://www.rayground.com"> <img src="img/rg.png" alt="rg" width="40" height="20" title="rayground site"> </a>
<a href="papers/conferences/eg2020edu/paper.pdf"> <img src="img/pdf_32.png" alt="author-prepared version" title="author-prepared version"> </a>
<a href="papers/conferences/eg2020edu/paper.bib"> <img src="img/bibtex_32.png" alt="bibtex" title="bibtex"> </a>
<a href="https://youtu.be/isLY6yUIMMA"> <img src="img/youtube_26.png" alt="video" title="youtube video"> </a>
<a href="https://github.com/cgaueb/rayground"> <img src="img/github_32.png" alt="github" width="30" height="30" title="github"> </a>
<a href="https://diglib.eg.org/handle/10.2312/eged20201027"> <img src="img/eg.png" alt="cgf" width="31" height="20" title="cgf link"> </a>
</h4>
</div>
</div>
<div class="row">
<div class="col-sm-3">
<iframe src="https://www.rayground.com/embed/jLH9mQIOwyY?paused=true&spp=500" width="220" height="220" scrolling="no" class="shadow img-rounded center-block">
</iframe>
</div>
<div class="col-sm-9 text-justify">
<p>
In this paper, we present Rayground; an online, interactive education tool for richer in-class teaching and gradual self-study, which provides a convenient introduction into practical ray tracing through a standard shader-based programming interface. Setting up a basic ray tracing framework via modern graphics APIs, such as DirectX 12 and Vulkan, results in complex and verbose code that can be intimidating even for very competent students. On the other hand, Rayground aims to demystify ray tracing fundamentals, by providing a well-defined WebGL-based programmable graphics pipeline of configurable distinct ray tracing stages coupled with a simple scene description format. An extensive discussion is further offered describing how both undergraduate and postgraduate computer graphics theoretical lectures and laboratory sessions can be enhanced by our work, to achieve a broad understanding of the underlying concepts. Rayground is open, cross-platform, and available to everyone.
<br>
</p>
</div>
<div class="col-xs-12">
<hr> </div>
</div>
</div>
<div id="eg2017" class="row col-xs-12">
<div class="row text-center">
<div class="col-sm-7">
<h4>
<span class="label label-danger">A. A. Vasilakis✝</span> <span class="label label-default">K. Vardis✝</span> <span class="label label-default">G. Papaioannou✝</span> <span class="label label-default">K. Moustakas</span>
</h4>
<h4><span class="label label-info">Variable k-buffer using Importance Maps</span></h4>
<h4>
<span class="label label-warning">k-buffer</span>
<span class="label label-warning">perceptual metrics</span>
<span class="label label-warning">selective rendering</span>
<span class="label label-warning">multi-fragment rendering</span>
</h4> </div>
<div class="col-sm-5">
<h4><span class="label label-success">EG (Short), 2017, pp. 21-24</span></h4>
<h5><span class="glyphicon glyphicon-calendar" aria-hidden="true"></span> Lyon, France, Apr 2017</h5>
<h4>
<a href="papers/conferences/eg2017/paper.pdf"> <img src="img/pdf_32.png" alt="author-prepared version" title="author-prepared version"> </a>
<a href="papers/conferences/eg2017/presentation.pptx"> <img src="img/ppt_32.jpg" alt="presentation" title="presentation"> </a>
<a href="papers/conferences/eg2017/shaders.zip"> <img src="img/source_32.png" alt="shader source code" title="shader source code"> </a>
<a href="papers/conferences/eg2017/paper.bib"> <img src="img/bibtex_32.png" alt="bibtex" title="bibtex"> </a>
<a href="https://diglib.eg.org/handle/10.2312/egsh20171005"> <img src="img/eg.png" alt="cgf" width="31" height="20" title="cgf link"> </a>
</h4> </div>
</div>
<div class="row">
<div class="col-sm-3"> <img src="papers/conferences/eg2017/teaser.png" alt="eg2017 teaser" class="shadow img-rounded center-block" title="eg2017 teaser"> </div>
<div class="col-sm-9 text-justify">
<p> Successfully predicting visual attention can significantly improve many aspects of computer graphics and games. Despite the thorough investigation in this area, selective rendering has not addressed so far fragment visibility determination problems. To this end, we present the first ''selective multi-fragment rendering'' solution that alters the classic k-buffer construction procedure from a fixed-k to a variable-k per-pixel fragment allocation guided by an importance-driven model. Given a fixed memory budget, the idea is to allocate more fragment layers in parts of the image that need them most or contribute more significantly to the visual result. An importance map, dynamically estimated per frame based on several criteria, is used for the distribution of the fragment layers across the image. We illustrate the effectiveness and quality superiority of our approach in comparison to previous methods when performing order-independent transparency rendering in various, high depth-complexity, scenarios.
<br>
<br> ✝ <em>These authors contributed equally to this work.</em>
</p>
</div>
<div class="col-xs-12">
<hr> </div>
</div>
</div>
<div id="cgi2016" class="row col-xs-12">
<div class="row text-center">
<div class="col-sm-7">
<h4>
<span class="label label-danger">A. A. Vasilakis</span> <span class="label label-default">I. Fudos</span> <span class="label label-default">G. Antonopoulos</span>
</h4>
<h4><span class="label label-info">PPS: Pose-to-Pose Skinning of Animated Meshes</span></h4>
<h4>
<span class="label label-warning">skinning</span>
<span class="label label-warning">compression</span>
<span class="label label-warning">editing</span>
<span class="label label-warning">character</span>
<span class="label label-warning">animation</span>
</h4> </div>
<div class="col-sm-5">
<h4><span class="label label-success">CGI (Short), 2016, pp. 53-56</span></h4>
<h5><span class="glyphicon glyphicon-calendar" aria-hidden="true"></span> Heraklion, Crete, Greece, Jul 2016</h5>
<h4>
<a href="papers/conferences/cgi2016/paper.pdf"> <img src="img/pdf_32.png" alt="author-prepared version" title="author-prepared version"> </a>
<a href="papers/conferences/cgi2016/presentation.pptx"> <img src="img/ppt_32.jpg" alt="presentation" title="presentation"> </a>
<a href="papers/conferences/cgi2016/paper.bib"> <img src="img/bibtex_32.png" alt="bibtex" title="bibtex"> </a>
<a href="http://dl.acm.org/citation.cfm?id=2949049"> <img src="img/acm.png" alt="acm" width="26" height="27" title="acm portal link"> </a>
</h4> </div>
</div>
<div class="row">
<div class="col-sm-3"> <img src="papers/conferences/cgi2016/teaser.png" alt="cgi2016 teaser" class="shadow img-rounded center-block" title="cgi2016 teaser"> </div>
<div class="col-sm-9 text-justify">
<p> In computer graphics, animation compression is essential for efficient storage, streaming and reproduction of animated meshes. Previous work has presented efficient techniques for compression using skinning transformations to derive the animated mesh from a reference pose. We present a pose-to-pose approach to skinning animated meshes by observing that only small deformation variations will normally occur between consecutive poses. The transformations are applied so that a new pose is derived by deforming the geometry of the previous pose, thus maintaining temporal coherence in the parameter space, reducing approximation error and facilitating forward propagated editing of arbitrary poses. </p>
</div>
<div class="col-xs-12">
<hr> </div>
</div>
</div>
<div id="hpg2016" class="row col-xs-12">
<div class="row text-center">
<div class="col-sm-7">
<h4><span class="label label-default">K. Vardis</span> <span class="label label-danger">A. A. Vasilakis</span> <span class="label label-default">G. Papaioannou</span>
</h4>
<h4><span class="label label-info">DIRT : Deferred Image-based Ray Tracing</span></h4>
<h4>
<span class="label label-warning">rasterization</span>
<span class="label label-warning">analytic ray tracing</span>
<span class="label label-warning">deferred rendering</span>
<span class="label label-warning">memory-aware</span>
</h4> </div>
<div class="col-sm-5">
<h4><span class="label label-success">HPG, 2016, pp. 1-11</span></h4>
<h5><span class="glyphicon glyphicon-calendar" aria-hidden="true"></span> Dublin, Ireland, Jun 2016</h5>
<h4>
<a href="http://kostasvardis.com/files/research/dirt_hpg2016_author_version.pdf"> <img src="img/pdf_32.png" alt="author-prepared version" title="author-prepared version"> </a>
<a href="http://www.kostasvardis.com/files/research/dirt_hpg2016.pptx"> <img src="img/ppt_32.jpg" alt="presentation" title="presentation"> </a>
<a href="http://graphics.cs.aueb.gr/graphics/downloads/DIRTDemo.zip"> <img src="img/demo_32.png" alt="demo" title="demo"> </a>
<a href="http://kostasvardis.com/files/research/dirt_hpg2016_shader_source.zip"> <img src="img/source_32.png" alt="shader source code" title="shader source code"> </a>
<a href="papers/conferences/hpg2016/paper.bib"> <img src="img/bibtex_32.png" alt="bibtex" title="bibtex"> </a>
<a href="https://diglib.eg.org/handle/10.2312/hpg20161193"> <img src="img/eg.png" alt="eg" width="26" height="20" title="eg link"> </a>
</h4> </div>
</div>
<div class="row">
<div class="col-sm-3"> <img src="papers/conferences/hpg2016/teaser.jpg" alt="hpg2016 teaser" class="shadow img-rounded center-block" title="hpg2016 teaser"> </div>
<div class="col-sm-9 text-justify">
<p> We introduce a novel approach to image-space ray tracing ideally suited for the photorealistic synthesis of fully dynamic environments at interactive frame rates. Our method, designed entirely on the rasterization pipeline, alters the acceleration data structure construction from a per-fragment to a per-primitive basis in order to simultaneously support three important, generally conflicting in prior art, objectives: fast construction times, analytic intersection tests and reduced memory requirements. In every frame, our algorithm operates in two stages: A compact representation of the scene geometry is built based on primitive linked-lists, followed by a traversal step that decouples the ray-primitive intersection tests from the illumination calculations; a process inspired by deferred rendering and the path integral formulation of light transport. Efficient empty space skipping is achieved by exploiting several culling optimizations both in xy- and z-space, such as pixel frustum clipping, depth subdivision and lossless buffer down-scaling. An extensive experimental study is finally offered showing that our method advances the area of image-based ray tracing under the constraints posed by arbitrarily complex and animated scenarios. </p>
</div>
<div class="col-xs-12">
<hr> </div>
</div>
</div>
<div id="i3d2016" class="row col-xs-12">
<div class="row text-center">
<div class="col-sm-7">
<h4><span class="label label-default">K. Vardis</span> <span class="label label-danger">A. A. Vasilakis</span> <span class="label label-default">G. Papaioannou</span> </h4>
<h4><span class="label label-info">A Multiview and Multilayer Approach for Interactive Ray Tracing</span></h4>
<h4>
<span class="label label-warning">A-buffer</span>
<span class="label label-warning">rasterization</span>
<span class="label label-warning">cubemap</span>
<span class="label label-warning">ray tracing</span>
<span class="label label-warning">path tracing</span>
<span class="label label-warning">ambient occlusion</span>
</h4> </div>
<div class="col-sm-5">
<h4><span class="label label-success">I3D, 2016, pp. 171-178</span></h4>
<h5><span class="glyphicon glyphicon-calendar" aria-hidden="true"></span> Redmond, WA, USA, Feb 2016</h5>
<h4>
<a href="http://graphics.cs.aueb.gr/graphics/docs/papers/IRT-i3D2016-av.pdf"> <img src="img/pdf_32.png" alt="author-prepared version" title="author-prepared version"> </a>
<a href="http://www.kostasvardis.com/files/research/mmrt_i3d2016.pptx"> <img src="img/ppt_32.jpg" alt="presentation" title="presentation"> </a>
<a href="http://kostasvardis.com/files/research/i3d2016-demo.7z"> <img src="img/demo_32.png" alt="demo" title="demo"> </a>
<a href="http://graphics.cs.aueb.gr/graphics/downloads/i3d2016-source_code-cr.zip"> <img src="img/source_32.png" alt="shader source code" title="shader source code"> </a>
<a href="papers/conferences/i3d2016/paper.bib"> <img src="img/bibtex_32.png" alt="bibtex" title="bibtex"> </a>
<a href="http://graphics.cs.aueb.gr/graphics/media/i3d2016-paper102.mp4"> <img src="img/video_26.png" alt="video" title="download video"> </a>
<a href="https://www.youtube.com/watch?v=0yLrVZGNFlA"> <img src="img/youtube_26.png" alt="video" title="youtube video"> </a>
<a href="https://dx.doi.org/10.1145/2856400.2856401"> <img src="img/acm.png" alt="acm" width="26" height="27" title="acm portal link"> </a>
</h4> </div>
</div>
<div class="row">
<div class="col-sm-3"> <img src="papers/conferences/i3d2016/teaser.jpg" alt="i3d2016 teaser" class="shadow img-rounded center-block" title="i3d2016 teaser"> </div>
<div class="col-sm-9 text-justify">
<p> We introduce a generic method for interactive ray tracing, able to support complex and dynamic environments, without the need for precomputations or the maintenance of additional spatial data structures. Our method, which relies entirely on the rasterization pipeline, stores fragment information for the entire scene on a multiview and multilayer structure and marches through depth layers to capture both near and distant information for illumination computations. Ray tracing is efficiently achieved by concurrently traversing a novel cube-mapped A-buffer variant in image space that exploits GPU-accelerated double linked lists, decoupled storage, uniform depth subdivision and empty space skipping on a per-fragment basis. We illustrate the effectiveness and quality of our approach on path tracing and ambient occlusion implementations in scenarios, where full scene coverage is of major importance. Finally, we report on the performance and memory usage of our pipeline and compare it against GPGPU ray tracing approaches. </p>
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<div id="eg2015" class="row col-xs-12">
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<h4><span class="label label-danger">A. A. Vasilakis</span> <span class="label label-default">G. Papaioannou</span> </h4>
<h4><span class="label label-info">Improving k-buffer methods via Occupancy Maps</span></h4>
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<span class="label label-warning">k-buffer</span>
<span class="label label-warning">occupancy maps</span>
<span class="label label-warning">culling</span>
<span class="label label-warning">multi-fragment rendering</span>
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<h4><span class="label label-success">EG (Short), 2015, pp. 69-72</span></h4>
<h5><span class="glyphicon glyphicon-calendar" aria-hidden="true"></span> Zurich, Switzerland, May 2015</h5>
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<a href="papers/conferences/eg2015/paper.pdf"> <img src="img/pdf_32.png" alt="author-prepared version" title="author-prepared version"> </a>
<a href="papers/conferences/eg2015/presentation.pptx"> <img src="img/ppt_32.jpg" alt="presentation" title="presentation"> </a>
<a href="papers/conferences/eg2015/presentation_ff.pptx"> <img src="img/ppt_32.jpg" alt="FF presentation" title="FF presentation"> </a>
<a href="papers/conferences/eg2015/shaders.zip"> <img src="img/source_32.png" alt="shader source code" title="shader source code"> </a>
<a href="papers/conferences/eg2015/paper.bib"> <img src="img/bibtex_32.png" alt="bibtex" title="bibtex"> </a>
<a href="https://diglib.eg.org/handle/10.2312/egsh.20151017.069-072"> <img src="img/eg.png" alt="eg" width="26" height="20" title="eg link"> </a>
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<div class="col-sm-3"> <img src="papers/conferences/eg2015/teaser.png" alt="eg2015 teaser" class="shadow img-rounded center-block" title="eg2015 teaser"> </div>
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<p> In this work, we investigate an efficient approach to treat fragment racing when computing k-nearest fragments. Based on the observation that knowing the depth position of the k-th fragment we can optimally find the k-closest fragments, we introduce a novel fragment culling component by employing occupancy maps. Without any software redesign, the proposed scheme can easily be attached at any k-buffer pipeline to efficiently perform early-z culling. Finally, we report on the efficiency, memory space, and robustness of the upgraded k-buffer alternatives providing comprehensive comparison results. </p>
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<div id="i3d2015" class="row col-xs-12">
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<h4><span class="label label-danger">A. A. Vasilakis</span> <span class="label label-default">G. Papaioannou</span> </h4>
<h4><span class="label label-info">Αccelerating k+-buffer using Efficient Fragment Culling</span></h4>
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<span class="label label-warning">k-buffer</span>
<span class="label label-warning">occupancy maps</span>
<span class="label label-warning">culling</span>
<span class="label label-warning">multifragment rendering</span>
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<h4><span class="label label-success">I3D (Posters), 2015, pp. 129-129</span></h4>
<h5><span class="glyphicon glyphicon-calendar" aria-hidden="true"></span> San Francisco, CA, USA, Feb-Mar 2015</h5>
<h4>
<a href="papers/conferences/i3d2015/paper.pdf"> <img src="img/pdf_32.png" alt="author-prepared version" title="author-prepared version"> </a>
<a href="papers/conferences/i3d2015/presentation_ff.pptx"> <img src="img/ppt_32.jpg" alt="FF presentation" title="FF presentation"> </a>
<a href="papers/conferences/i3d2015/poster.pdf"> <img src="img/poster_32.png" alt="poster" title="poster"> </a>
<a href="papers/conferences/i3d2015/paper.bib"> <img src="img/bibtex_32.png" alt="bibtex" title="bibtex"> </a>
<a href="https://dl.acm.org/citation.cfm?doid=2699276.2721402"> <img src="img/acm.png" alt="acm" width="26" height="27" title="acm portal link"> </a>
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<div class="col-sm-3"> <img src="papers/conferences/i3d2015/teaser.png" alt="i3d2015 teaser" class="shadow img-rounded center-block" title="i3d2015 teaser"> </div>
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<p> In this work, we investigate an efficient approach to treat fragment racing when computing k-nearest fragments. Based on the observation that knowing the depth position of the k-th fragment we can optimally find the k-closest ones, we introduce a novel orderindependent fragment culling component, easily attached to the k+ buffer pipeline. An additional rendering pass of the scene’s geometry is initially employed to construct a per pixel binary fragment occupancy discretization. Then, the nearest depth of the k-th per pixel fragment is concurrently computed by performing bit counting operations and subsequently utilized to perform early-z rejection for the k+ buffer construction process that follows. Any fragment with depth larger than this value will fail the depth test, avoiding the cost of its pixel shading execution. Note that no software modifications are required to the actual k+ buffer implementation. </p>
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<div id="eg2014" class="row col-xs-12">
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<h4><span class="label label-default">E. Eftaxopoulos</span> <span class="label label-danger">A. A. Vasilakis</span> <span class="label label-default">I. Fudos</span> </h4>
<h4><span class="label label-info">AR-TagBrowse: Annotating and Browsing 3D models on Mobile Devices</span></h4>
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<span class="label label-warning">augmented reality</span>
<span class="label label-warning">annotation</span>
<span class="label label-warning">mobile</span>
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<h4><span class="label label-success">EG (Posters), 2014, pp. 1-1</span></h4>
<h5><span class="glyphicon glyphicon-calendar" aria-hidden="true"></span> Strasbourg, France, May 2014</h5>
<h4>
<a href="papers/conferences/eg2014/paper.pdf"> <img src="img/pdf_32.png" alt="author-prepared version" title="author-prepared version"> </a>
<a href="papers/conferences/eg2014/poster.pdf"> <img src="img/poster_32.png" alt="poster" title="poster"> </a>
<a href="papers/conferences/eg2014/paper.bib"> <img src="img/bibtex_32.png" alt="bibtex" title="bibtex"> </a>
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<div class="col-sm-3"> <img src="papers/conferences/eg2014/teaser.png" alt="eg2014 teaser" class="shadow img-rounded center-block" title="eg2014 teaser"> </div>
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<p> We report on the development of a novel interactive augmented reality app called AR-TagBrowse, built on Unity 3D that enables users to tag and browse 3D objects. Users upload 3D objects (polygonal representation and diffuse maps) through a web server. 3D objects are then linked to real world information such as images and GPS location. Users may optionally segment the objects into areas of interest. Such objects will subsequently pop up in the AR-TagBrowse app when one of these events is detected (visible location or image). The user is then capable of interactively viewing the 3D object, browsing tags or entering new tags providing comments or information for specific parts of the object. </p>
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<h4><span class="label label-danger">A. A. Vasilakis</span> <span class="label label-default">I. Fudos</span> </h4>
<h4 class="text-danger"><span class="label label-info ">k+-buffer: Fragment Synchronized k-buffer</span>
<a href="https://www.flickr.com/photos/mvives/13387936565/in/set-72157642866815403">★</a>
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<span class="label label-warning">k-buffer</span>
<span class="label label-warning">A-buffer</span>