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%\date{}
%\title{Introduction}
%\author{Steve Seitz \\
%Carnegie Mellon University \\
%\and
%Brian Curless \\
%University of Washington
%}
%\author{}

%\maketitle
\vspace{0.3in}
\centerline{\Huge Introduction}
\vspace{0.3in}

3D photography is an emerging technology for capturing richly detailed
models of objects in the real world.  Whereas traditional optical cameras
capture scene appearance in the form of radiant light energy, 3D photographs
measure surface characteristics like 3D geometry and reflectance---exactly
what is needed to construct graphical models.
Consequently this technology provides a means for acquiring
graphical objects and scenes of unprecedented detail and realism 
by {\em scanning} 
them in from the real world.

Methods to digitize and reconstruct the shapes of complex three
dimensional objects have evolved rapidly in recent years.  The speed
and accuracy of digitizing technologies owe much to advances in the
areas of physics and electrical engineering, including the development
of lasers, CCD's, and high speed sampling and timing circuitry.  
Such technologies allow us to take detailed shape measurements with
precision better than 1 part per 1000 at rates exceeding 10,000
samples per second.  To capture the complete shape of an object, many
thousands, sometimes millions of samples must be acquired.  The
resulting mass of data requires algorithms that can efficiently and
reliably generate computer models from these samples.  The future of
3D photography will see systems that capture precise geometry and 
reflectance information at even larger spatial scales,
enabling the acquisition of landscapes and complex urban scenes, and fast
scanners that enable 3D video at real-time rates.

The applications of 3D photography are
wide-ranging and include manufacturing, virtual simulation, scientific
exploration, medicine, and consumer marketing.


\subsubsection*{Dissemination of museum artifacts}

Museum artifacts represent one-of-a-kind objects that attract the
interest of scientists and lay people world-wide.  Traditionally, to
visualize these objects, it has been necessary to visit potentially
distant museums or obtain non-interactive images or video sequences.
By digitizing these parts, museum curators can make them available for
interactive visualization.  For scientists, computer models afford the
opportunity to study and measure artifacts remotely using powerful
computer tools.  A case in point is the 
{\em Digital Michelangelo Project}
headed by Marc Levoy at Stanford University.  The goal of this multi-year 
project is to create a high-quality 3D computer archive of the sculptures 
and architecture of Michelangelo.  This course features the first 
presentation of the Digital Michelangelo Project to the SIGGRAPH community.

\subsubsection*{Special effects, games, and virtual worlds}

Synthetic imagery is playing an increasingly prominent role in
creating special effects for cinema.  In addition, video games and
gaming hardware are moving steadily toward interactive 3D graphics.
Virtual reality as a means of simulating worlds of experience is also
growing in popularity.  All of these applications require 3D models
that may be taken from real life or from sculptures created by
artists.  Digitizing the shapes of physical models will be essential
to populating these synthetic environments.

\subsubsection*{Reverse engineering}

Many manufacturable parts are currently designed with Computer Aided
Design (CAD) software.  However, in some instances, a mechanical part
exists and belongs to a working system but has no computer model
needed to regenerate the part.  This is frequently the case for
machines currently in service that were designed before the advent of
computers and CAD systems, as well as for parts that were hand-tuned
to fit into existing machinery.  If such a part breaks, and neither
spare parts nor casting molds exist, then it may be possible to remove
a part from a working system and digitize it precisely for
re-manufacture.

\subsubsection*{Collaborative design}

While CAD tools can be helpful in designing parts, in some cases the
most intuitive design method is physical interaction with the model.
This is especially true when the model must have esthetic appeal, such
as the exteriors of consumer products ranging from perfume bottles to
automobiles.  Frequently, companies employ sculptors to design these
models in a medium such as clay.  Once the sculpture is ready, it may
be digitized and reconstructed on a computer.  The computer model is
then suitable for dissemination to local engineers or remote clients
for careful review, or it may serve as a starting point for
constructing a CAD model suitable for manufacture.


%\subsection*{Inspection}
%
%After a manufacturer has created a computer model for a part either by
%shape digitization of a physical model or through interactive CAD
%design, he has a variety of options for creating this part, both as a
%working prototype and as a starting point for mass manufacture.
%Ultimately, the dimensions of the final manufactured part must fall
%within some tolerances of the original computer model.  In this case,
%shape digitization can aid in determining where and to what extent the
%computer model and the shape of the actual part differ.  These
%differences can serve as a guide for modifying the manufacturing
%process until the part is acceptable.

%Some of these options include injection molding, metal casting, CNC
%milling, die stamping, and rapid prototyping.

\subsubsection*{Medicine}

Applications of 3D Photography in medicine are wide ranging as
well.  Prosthetics can be custom designed when the dimensions of the
patient are known to high precision.  Plastic surgeons can use the
shape of an individual's face to model tissue scarring processes and
visualize the outcomes of surgery.  When performing radiation
treatment, a model of the patient's shape can help guide the doctor in
directing the radiation accurately. 


\subsubsection*{Home shopping}

As the World Wide Web provides a backbone for interaction over the
Internet, commercial vendors are taking advantage of the ability to
market products through this medium.  By making 3D models of their
products available over the Web, vendors can allow the customer to
explore their products interactively.  Standards for disseminating 3D
models over the web are already underway (e.g., the Virtual Reality
Modeling Language (VRML)).

\subsection*{Course Objectives}

In this course we will focus on the technology underlying the field of
3D photography, focusing on the current state-of-the-art and the principles
underlying several leading approaches.  Our intent is to cover the 
fundamentals but also to give an understanding of current research 
directions and and exciting applications.
With these objectives in mind we have designed a course
that brings together several leading researchers and practitioners
to present state-of-the-art 3D photography approaches from the ground up.

The course will cover a variety of methods for recovering shape from images.
Introductory material will describe the fundamentals of cameras, from
lenses to CCD's, and ways of calibrating them.  Several passive vision methods
will be presented, including stereo, structure from motion, shape from shading,
volume intersection, and voxel coloring.  Active vision methods will include
imaging radar, optical triangulation, moire, active stereo, active depth
from defocus, and desktop shadow striping.  The course concludes with a
field study:  capturing 3D photographys of Michelangelo's statues.

We hope the material in this volume will prove useful to you to help gain
a deeper understanding of the concepts behind 3D photography, but moreover
to help you build your own 3D photography system on your desktop.  To this
end, we have provided material that we believe is sufficient to design
and build practical 3D photography systems from scratch.

\begin{flushright}
Steve Seitz \\
Brian Curless \\
April 1999 \\
\end{flushright}

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