% $Id: template.tex 11 2007-04-03 22:25:53Z jpeltier $

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\title{GPU-Based Volume Ray-Casting with Advanced Illumination}

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%%\author{Roy G. Biv\thanks{e-mail: roy.g.biv@aol.com}}
%%\affiliation{\scriptsize Allied Widgets Research}

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%%\author{Roy G. Biv\thanks{e-mail: roy.g.biv@aol.com} %
%%\and Ed Grimley\thanks{e-mail:ed.grimley@aol.com} %
%%\and Martha Stewart\thanks{e-mail:martha.stewart@marthastewart.com}}
%%\affiliation{\scriptsize Martha Stewart Enterprises \\ Microsoft Research}

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\author{}

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%% Abstract section.
\abstract{GPU-based ray-casting techniques are becoming more and more important
for the visualization of volume data in medicine and engineering. Thanks to their
flexibility and accuracy, they will likely replace existing slice-based techniques in the
near future. The tutorial targets the growing number of developers who work on specialized
implementations of volume rendering algorithms on state-of-the-art graphics hardware.

The tutorial begins with a detailed introduction to the concepts behind
GPU-based ray-casting. Major focus of this tutorial are advanced illumination effects, which
are important to improve the spatial perception. Such effects include soft and hard shadows,
advanced illumination effects such as translucency and multiple scattering. The tutorial focuses strongly upon
aspects relevant for scientific visualization, but also covers topics more related to visual arts.
} % end of abstract

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{Project and People Management}{Life Cycle};
  \CCScat{K.7.m}{The Computing Profession}{Miscellaneous}{Ethics}
}

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%%%%%%%%%%%%%%%%%%%%%% START OF THE PAPER %%%%%%%%%%%%%%%%%%%%%%
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\begin{document}

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\firstsection{Tutorial Duration}

\maketitle

\textbf{1/2 day} tutorial.



\section{Level of the Tutorial}

\textbf{Intermediate to advanced}. The tutorial is aimed at scientific researchers and developers of
visualization tools. Course participants should have basic programming skills and should be familiar with graphics hardware
and shading languages. We will assume a basic knowledge regarding volume data as well as interactive volume rendering techniques. Furthermore, a basic understanding of GPU techniques is required.



\section{Tutorial Description}

We will present an in-depth tutorial to GPU-based ray-casting
approaches to volume visualization supporting advanced illumination
models. Participants will learn how to leverage the new features of
modern commodity graphics hardware to implement advanced illumination
techniques for high-quality volume rendering applications. Thus they
should be able to target new research directions towards visualization
techniques exploiting advanced shading models as well as to improve
the existing shading models, which can be applied interactively.

The tutorial starts with an introduction to the basic principles of
GPU-based volume ray-casting, including useful optimization
techniques, which are necessary to support advanced illumination
models. After these issues have been discussed existing interactive
illumination models for GPU-based volume ray-casting are explained in
detail.

Thus, besides the basic implementation details, the following topics
are covered:
\begin{itemize}
\item Memory Management
\item Space Leaping and Early Ray Termination
\item Soft and Hard Shadows, Semitransparent Shadows
\item Diffuse and Specular Light Interactions
\item Translucency and Multiple Scattering Effects
\item Monte-Carlo based Illumination Techniques
\end{itemize}

Participants are provided with implementation details often omitted in scientific publications.

We feel that it is important to demonstrate these ideas since the reality of implementation can be quite different from
the theory presented in the scientific literature. Since the content of the tutorial can be quite challenging, we intend to answer questions on the fly.

\section{Instructors Background and Contact Information}


\noindent\begin{minipage}{\linewidth}
\noindent{\bfseries Markus Hadwiger}\\
VRVis Research Center for Virtual Reality and Visualization\\
Donau-City-Stra\ss{}e 1\\
A-1220 Vienna, Austria\\
Email: {\tt msh@vrvis.at}\\
\end{minipage}\\
\smallskip

\noindent {\bfseries Markus Hadwiger} is a senior researcher at the VRVis Research Center in Vienna, Austria. He received his Ph.D. in computer science from the Vienna University of Technology in 2004, and has been a researcher at VRVis since 2000, working in the Basic Research on Visualization group and the Medical Visualization group (since 2004). He has been involved in several courses and tutorials about volume rendering and visualization at ACM SIGGRAPH, IEEE Visualization, and Eurographics. He is a co-author of the book {\em Real-Time Volume Graphics} published by A K Peters.

\bigskip

\noindent\begin{minipage}{\linewidth}
\noindent{\bfseries Christof Rezk-Salama}\\
Computer Graphics Group\\
University of Siegen\\
Hoelderlinstr. 3\\
57066 Siegen, Germany\\
Email: {\tt rezk@fb12.uni-siegen.de}\\
\end{minipage}\\
\smallskip

\noindent{\bfseries Christof Rezk-Salama} has received a PhD from the University of
Erlangen-Nuremberg as a scholarship holder of the graduate college
{\em 3D Image Analysis and Synthesis}. He has worked as a research
engineer for the R\&D department of Siemens Medical Solutions. Since
October 2003 he is working as an assistant professor at the Computer
Graphics Group of the University of Siegen, Germany.

The results of his research have been presented at international
conferences, including ACM SIGGRAPH, IEEE Visualization,
Eurographics, MICCAI and Graphics Hardware. He is regularly holding
lectures, courses and seminars on computer graphics, scientific
visualization, character animation and graphics programming.

He has gained practical experience in applying computer graphics to
several scientific projects in medicine, geology and archaeology.
Christof Rezk-Salama has released the award winning open-source
project {\em OpenQVis} and is a co-author of the book {\em Real-Time
Volume Graphics}.

\bigskip

\noindent\begin{minipage}{\linewidth}
\noindent{\bfseries Patric Ljung} \\
Department of Imaging and Visualization\\
Siemens Corporate Research\\
755 College Road East\\
Princeton, NJ 08540, U.S.A.\\
Email: {\tt patric.ljung@siemens.com}
\end{minipage}\\

\smallskip

\noindent{\bfseries Patric Ljung} joined in 2007 Siemens Corporate Research in
Princeton, NJ, where he works as a Research Scientist in the Imaging
Architectures group.  He received 2006 his PhD in Scientific
Visualization from Link\"oping University, Sweden and graduated with
honors in 2000 his MS in Information Technology from Link\"oping
University.  Between 1989 and 1995 he worked as a software engineer
with embedded and telecom systems involving software architectures,
graphical user interfaces, voice-mail systems, communication
protocols, network and interprocess communication, compilers.

Dr. Ljung has published several papers in international conferences
and journals including IEEE Visualization, Eurographics conferences,
IEEE TVCG and others, on volume rendering of large medical data sets,
GPU-based raycasting of multiresolution data sets.  One important
focus area has been Virtual Autopsies for forensic pathology.  His
current research interest is in advanced illumination and shading
techniques, software architectures for extensible graphics, and
management and rendering of large medical data sets.

\onecolumn
\renewcommand{\arraystretch}{1.0}
\section{Contents and Schedule}
The half-day tutorial will consist of four different blocks, each of about 45 minute length. From a didactic point of view, each block will loosely build upon the 
information conveyes in previous blocks with growing complexity and increasing level of difficulty.

\smallskip

\noindent\begin{minipage}[t]{0.50\linewidth}

\noindent\textbf{ \large 8:30 -- 9.15: Introduction and Basics}\\[1mm]
{\it Speaker: Markus Hadwiger}

\begin{itemize}
\item Application Areas for Volume Rendering %(Medical, Seismic, CFD)
\item Benefits and Drawbacks of Ray-Casting
\item GPU-based Volume Ray-Casting %[Markus]
\item Space Leaping and Early Ray Termination %[Markus]
\item Memory Management %[Markus]
\item Multiresolution LOD and Adaptive sampling %[Patric]
\end{itemize}

GPU-based ray-casting is a volume rendering technique with a steadily growing popularity in scientific visualization. 
The first part of the tutorial gives an introduction to GPU-based ray-casting discussing the benefits and drawbacks compared to
previous real-time volume rendering approaches like 3D texture slicing. After this introductory part, the attendees should have a thorough 
understanding of how GPU-based ray-casting approaches work, and how they must be employed in practice to achieve optimal performance
This section covers optimization techniques such as empty space leaping, level-of-detail and adaptive sampling.
The implementation of spatial partitioning techniques, hierarchical data structures and memory management strategies for 
the handling of large volumes are explained in detail.

\end{minipage}
\hfill 
\begin{minipage}[t]{0.47\linewidth} 
\phantom{MMM}
\includegraphics[width=0.49\linewidth]{009.eps}
\includegraphics[width=0.49\linewidth]{011.eps}
\includegraphics[width=0.49\linewidth]{012.eps} 
\includegraphics[width=0.49\linewidth]{plg-slide2.eps}
\includegraphics[width=0.49\linewidth]{plg-slide3.eps}
\includegraphics[width=0.49\linewidth]{plg-slide4.eps}
\end{minipage}

\bigskip

\noindent\begin{minipage}[t]{0.48\linewidth}
\noindent\textbf{\large 9:15 -- 10.00: Light Interaction}\\[1mm]
{\it Speaker: Christof Rezk-Salama}
\begin{itemize}
\item Light Transport and Illumination Models%[Christof]
\item Local Volume Illumination
\item Ray-Traced Specular Reflections %[Timo]
\item Monte-Carlo Integration
\item Overview of Global Illumination Techniques
\begin{itemize}
\item Ray-Traced Shadows for Isosurfaces %[Christof]
\item Ambient Occlusion for Isosurfaces
\end{itemize}
\end{itemize}

This part gives an overview to physically-based light transport introducing 
the phase function as a volumetric equivalent to the bidirectional reflectance distribution function (BRDF) known from surface lighting.
This part covers basic local illumination techniques with respect to GPU-based ray-casting, including run-time gradient estimation, as well 
as more advanced local illumination techniques for volume data and isosurfaces . Additionally this 
block introduces the important prerequisites for the following parts. The principles of Monte-Carlo integration are explained 
using several examples that are easy to understand. An coarse overview of global illumination techniques for volume data and implicit surfaces
are given. After this part, the attendees should have a basic understanding how physically based light transport is described in volume, and what 
the different effects of light-matter interactions are in participating media. The principles of highly approximative techniques such as 
ambient occlusion are explained, which is a state-of-the-art technique loosely based upon radiosity calculations.
\end{minipage}
\hfill 
\begin{minipage}[t]{0.50\linewidth}
\phantom{MMMM}
\includegraphics[width=0.49\linewidth]{015.eps}
\includegraphics[width=0.49\linewidth]{001.eps}
\includegraphics[width=0.49\linewidth]{002.eps}
\includegraphics[width=0.49\linewidth]{008.eps}
\includegraphics[width=0.49\linewidth]{004.eps}
\includegraphics[width=0.49\linewidth]{016.eps}
\end{minipage}

\bigskip

\noindent\begin{minipage}[t]{0.48\linewidth}
\noindent\textbf{\large 10:30 -- 11.15: Shadows}\\[1mm]
{\it Speaker: Timo Ropinski}
\begin{itemize}
\item  Soft vs. Hard Shadows %[Timo]
\item  Deep Shadow Maps %[Markus]
\item  Local Ambient Occlusion (DVR) %[Patric]
\item  Dynamic Ambient Occlusion (DVR) %[Timo]
\item  Semi-Transparent Shadows %[Timo]
\end{itemize}

For scientific visualization, the inclusion of shadows into volume rendering systems significantly increases 
the perception of spatial structures and depth relationships. This part covers state-of-the art techniques for shadow computation 
in semitransparent volume renditions, including soft and hard shadows. We will show how hard shadows can be computed 
interactively using efficient GPU-based approaches such as deep shadow maps. Soft shadows may be approximated using ambient occlusion techniques for semitransparent 
volumes and dynamic illumination scenarios.
\end{minipage}
\hfill
\begin{minipage}[t]{0.50\linewidth}
\phantom{MMMM}
%\includegraphics[width=0.49\linewidth]{013.eps}
\includegraphics[width=0.49\linewidth]{014.eps}
\includegraphics[width=0.49\linewidth]{plg-slide6.eps}
\includegraphics[width=0.49\linewidth]{006.eps}
\includegraphics[width=0.49\linewidth]{plg-slide7.eps}
%& \includegraphics[width=0.3\linewidth]{plg-slide5.eps}~\includegraphics[width=0.3\linewidth]{007.eps}\\
\end{minipage}

\bigskip

\noindent\begin{minipage}[t]{0.48\linewidth}
\noindent\textbf{\large 11:15 -- 12.00: Scattering}\\[1mm]
{\it Speaker: Patric Ljung}
\begin{itemize}
\item Single versus Multiple Scattering
\item Color Bleeding %[Timo, Patric]
\item Translucency 
\item Monte-Carlo Scattering %[Christof]
\item First-order Multiple Scattering %[Patric]
\item Scattering with Deep Shadow Maps %[Markus]
%\item Color Bleeding [Timo]
\end{itemize}
Scattering effects account for photons which are reflected multiple times before they reach the eye. For volumetric
data, scattering effects are usually included to capture the visual appearance of participating media. Such effects 
are important for modeling of natural phenomena such as smoke and clouds in visual arts. For scientific visualization, 
volume scattering may be used to convey tissue properties in a realistic way. Translucency is an important visual property 
of soft tissue. This part of the tutorial covers interactive implementations of both single and multiple 
scattering effects in volumes. In order to implement scattering and translucency in scientific data, slightly different approaches 
must be chosen in order to convey the structures in tomographic scans, compared to visual arts where the optical properties inside the volume 
are mostly assumed homogeneous. Several state-of-the-art approaches to achieve multiple scattering effects including 
color bleeding and translucency for interactive volume graphics are explained.

\end{minipage}
\hfill
\begin{minipage}[t]{0.50\linewidth}
\phantom{MMMM}
\includegraphics[width=0.49\linewidth]{010.eps}
\includegraphics[width=0.49\linewidth]{003.eps}
\includegraphics[width=0.49\linewidth]{005.eps}
\end{minipage}
%\noindent\textbf{11:30 -- 12.00: Open Issues}\\
%\begin{tabular}{ll}
%\end{tabular}\\

\twocolumn

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