On Photon Mapping
Publisher: Premier Press
- RRP US$23.99
Reviewed: 9th February 2004
Mapping is one of the new-breed of global
illumination techniques; that is -
lighting/rendering algorithms that generate
extremely realistic results. They aren't overly
new (many of the algorithms have been around for a
decade or more), but they are increasing in
popularity due to the advent of faster and faster
desktop computers - it is now possible to render a
photon mapped scene in under an hour!
subject of global illumination is an interesting
target for a 'Focus-On' book, as they are often
fairly light-weight book giving an
applied-to-the-point spin on a larger topic.
Photon Mapping is no simple topic... so this
concept of an applied-to-the-point text is going
to be interesting.
reference, 3 other books have been reviewed by
this website covering aspects of global
Ray Tracing (first edition)
Ray Tracing (second edition)
previously stressed, Photon Mapping is not trivial
- yet having read through this book I have found
it to be amazingly accessible. By comparison to
the three books referenced above, this book can be
read and understood with very little effort.
first half of this book is pretty much dedicated
to theory - yet there is no mathematical
derivations, proofs or theories. All explanation
is done in plain text with a significant number of
supporting diagrams. Even the diagrams have a
friendly, if slightly childish (reminds me of my 'GCSE'
(ages 15-16 education in the UK) text books
), feel to them. Given that the physics of light
transport is a core theory for global
illumination, seeing it explained with relatively
simple diagrams makes for a refreshing change to
the vector mathematics employed by many other text
this simplicity will become a weakness after the
first couple of attempts at implementing the
features in this book, or more importantly, it
will not take you much further than this book.
Extending the ideas to make a more comprehensive
engine, or just altering the code to use more
complex functions will require that you read
through various online white papers - and believe
me, that won't be a pleasant jump from this book.
applied half of this book is pretty much focused
on the generation of static images from a static
scene. For a book of this size it would be unfair
to expect it to be too general - focusing on a
particular aspect of photon mapping and
demonstrating it clearly is the aim here; you'll
want one of the bigger text books if you want a
complete discussion of the entire field of photon
static imagery is one of the key areas of photon
mapping (used by programs such as 3DSMax to
generate ultra realistic images), it is not that
useful when it comes to games development.
that use photon mapping need to pre-process the
light received by each surface in an environment,
traditionally storing it in a 2D texture called a
'light map'. This light map can then be rendered
in real-time, and as long as the objects/lights
don't move it will look perfectly realistic.
book generates a single image from a cameras point
of view - whilst the light received by each
surface is calculated at an intermediary step, it
isn't actually outputted. What is outputted is the
final image... great if you want a single frame
image, but not so great if you want to map it to a
3D world and use it in a real-time environment. To
do this you need all of those intermediary surface
values. The last chapters of the book do explain
this, but not in a detailed enough way to make it
immediately usable - it's up to you to write the
code, or work out just how this is done..
it's favor, this book is platform independent. The
programming language of choice is C++, as is
standard with almost all
programming/game-development books, but C++ is not
platform specific really.
book presents, what is essentially, a software
rasterizer that outputs a single image given a
scene and a view point. The actual graphical
output (be it Win32, DirectX, OpenGL...) is not
specified, and is relatively trivial to implement
on any of these API's.
CD contains a complete library of the source code
discussed in each chapter, so it is possible to
see the code in action, even if you do have to
wait a while (30mins for one of the samples on a
900mhz Laptop according to the author)!
book provides a good overview, and is a great
introductory text to photon mapping - but
unfortunately, it's nothing more than that. With a
reasonable dose of intelligence, you can take the
lessons learnt here and a few advanced articles
online and come up with a perfectly acceptable
from a game development perspective, it is quite
limited.. The last couple of chapters that deal
with converting the algorithm for use in a game
environment is a bit too vague. It discusses
per-vertex photon mapping - which is interesting,
but only in a general sense, and even then
per-pixel (through light maps) photon mapping is
almost skipped entirely.
Clear and intelligent writing style
Limited scope due to little mathematical
theory or applied light-mapping section
Important theory covered without too much
More suited to general computer graphics
than to game development.
Not API dependent
Good CD included with all examples and
Lots of tips from the author throughout