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History of Tracking  by mseymour7



Tracking is the process of automatically locating a point or series of
points from frame to frame in a sequence, allowing the user to
stablise, track to or solve object or camera movement in the shot. The
process started as one point tracking which could stablise a shot or
add matching motion to a composite. Today it involves complex 3D camera
solutions and extends to optical flow - the technology of tracking
every pixel in a shot. In this series, we will explore the history of
tracking, the best ways to shoot material for tracking, and provide an
overview of current key products. Along the way we've interviewed some
the men and women who invented the craft and many of the early adopters
who showed its potential.






A
VFX artist tracks or stablizes shots daily. Many also solve complex
multi-point tracks and 3D camera solutions. But little is known of the
inner algorithms that drive the software. By understanding exactly how
the motion tracking works, it is possible to improve solutions and
speed up work.





While it is increasingly true that almost any object or any scene can
be tracked, this is our craft and profession. We should aim for the
best results possible when on set and not allow the attitude of "fix it
in post" to stop us from producing the best work possible. According to
Doug Roble, Technical Academy Award winner for his TRACK software at
Digital Domain, this is very important. "We go the other way," he
states. "We measure everything on set, we are really exact. 20% of the
shots we solve are easy, 80% are hard. We focus on changing those odds".





The art of tracking has changed with the advent of 3D tracking with
tools such as 3D Equaliser, boujou, PixelFarm PFTrack, and RealViz
MatchMover. It is changing again with floating point optical flow
analysis from companies such as The Foundry and The Pixel Farm and
emerging new laser scanning technologies. In the third part of the Art
of Tracking series, we will take a brief look at these. While we will
touch on Optical Flow Technology and Open EXR, this subject is so large
they will be featuring in an upcoming Art of Optical Flow series.








Historical overview of tracking





Prior to digital tracking, in both electronic and optical effects, for
most effects shots the camera was locked off. It was just impossible
with out motion control of the capturing cameras to align to shots in
post-production. While hand tracking has been attempted, the eye is so
well adjusted to noticing movement and float - that often times sub
pixel accuracy is required to sell a shot and fool an audience.





ln the beginning ...





The US Defense Department first developed the concept of tracking for
use in missile guidance systems. The earliest VFX use of tracking is
perhaps in 1985 At the famous NYIT graphics lab Tom Brigham and
J.P.Lewis (now at ESC) implemented an FFT based tracker that was used
for a series of television commercials that we called the "rising coin"
series. These were commercials for National Geographic where a gold
coin traveled in an arc (as if it were a rising sun), and they had to
be stabilized to match the movement and jitter of the background
plates. ILM had an early 2D tracking software system called MM2 first
tested on Hook and Death Becomes Her. MM2 was not an automated tool,
but a manual 2d nudge tool where the artist would keyframe position
changes by hand. ILM would later use this as the basis of one of the
earliest 3D tracking systems which was used for Jurassic Park,
development headed by Mike Natkin. Much of the early ILM work was done
by J.P. Lewis now at USC's Graphics Lab and Rod Bogart who joined ILM
in 1995.





Lewis remembers, "At ILM I developed a Fourier-domain algorithm for
*normalized* cross-correlation. Fourier cross correlation was a well
known algorithm from the 60s (at least), but it was not known how to do
the improved normalized version in the frequency domain. ILM let me
publish the algorithm, and it was accepted to a vision converence,
Vision Interface 95. A version of the paper is online at http://www.idiom.com/~zilla/Work/nvisionInterface/nip.pdf


Since then this algorithm has spread around, including now being
implemented in the Matlab image processing toolbox, etc. Also, I
separately reimplemented it, and contributed the algorithm to a couple
of packages including Shake and Commotion."






Joe
Alter developed one of the earliest markerless tracking systems
"tga_stablize" on an IBM PCAT(286) with Truevision Targa 32 card to
match two morph plates for Star Trek, The Next Generation in early
1991. "Later that year I re-wrote it for the SGI PI-30 and the IBM-PVS
parallel super computer at Boss Film for use in Cliffhanger," explains
Alter. "I was the a lead TD along with Andy White, under CG Supervisor
Jim Rygel (now at WETA). The utils were called ?rle_coarse? (for pixel
level tracking), ?rle_fine? for subpixel tracking, and 'rle_track'
(adapted from Graphics Gems witness point tracking util) for finding 3d
camera positions from point data."















On
the 1993 feature film Cliffhanger, Andy White took the tracking data
and fed it into textured polygon corners in wavefront TAV to cover up
holes in the set construction (a fake cliff with 2 by 4s sticking out),
and Alter used it to reconstruct clean plates from moving cameras for
rig removal and tracking of the live plates into various matte
paintings. Boss Film did excellent work, but Alter would later move on
to join the ILM's team in '94.





It was Discreet who first brought tracking to the broader visual
effects community in their landmark Flame system. Discreet lead the
field for many years with their innovative and brilliant tracking
developments. Emmy-winner Wally Rodriguez, of Miami visual effects
studio Upstairs
comments, "It (tracking) was in the first version we got of flame and
depending on who you talk to Jake Parker and I were either delivered
second or third systems. (The very first non-feature film system was
delivered in the US to a place called "Walk the Bible Productions" in
Atlanta). - Tracking and timewarping were the big sellers for us." .





LA flame artist Maribeth Emigh relates, "For the first version I had of flame (and I was one of the first past the mario flames [ed. Mario Brothers feature film unit]),
I remember a 1.0 scribbled on the exabyte I had. It had 1 point
tracking...and it worked rather well but limited for just one point.
You looked for the highest contrast and could only do frames and
forward.... but at the time the fact that you could track at all saved
tons of time."








1992





Flame started life as Flash - written in the suburbs of Melbourne
Australia by Gary Tregaskis. Tregaskis, who has long since moved away
from Flame and Discreet wrote Flash and it moved to Canada and the
newly formed Discreet Logic. Flame was first shown at NAB 1992 and
offically launched at Sigrapph 1992.






Ken
Deaton wrote in the June 1992 issue of Video Innovations "You're afraid
to ask what's next - I can tell you still think your black box can beat
my Eddie then you should know that Eddie has a big brother, Flame.
Flame is also brought to you by the folks at Discreet Logic. If you
can't get your head around all that jazz that EDDIE does, try imagine
EDDIE on steroids with a near-real-time attitude. That's because FLAME
utilizes the aggressive graphics processing power of SGI VGX
computers'. Big Box. Rather expensive one too. It helps to have an
Abekas recorder too (doesn't it always). But if you have the funds,then
you can have some fun doing that morphing thing, right up to IMAX
resolution. I would tell you more about it, but I can't afford it,
anyway. Besides it's just in beta now and doesn't officially debut
until SIGGRAPH this summer. Remember you heard it here first".





In an exclusive, Tregaskis spoke to fxguide about the moment he
invented tracking for flame, "Tracking... Hmmm... Well, I first thought
of tracking way way back in the early 90's... I was at a facility in
LA... Rich Thorn's facility... Can't remember the name of it..(ed.
Digital Magic), while watching a Harry operator working on a shot of a
car falling over a cliff... He was manually trying to composite a shape
over one of the windows of the car to obscure what was inside (or the
fact that no one was inside)... It was remarkably unsuccessful as the
shot was shaking all over the place and the angle of the window kept
changing... I thought there had to be a better way... So went home and
wrote it... It was back in the days when CPUs ran as fast as a washing
machine processor... So the only way to get it to run at any decent
speed was to pump the image data through the accumulation buffer...
Using the accumulation buffer to perform mathematical operations on
each pixel simultaneously... It worked well for a first
implementation... But was subsequently blown away by much faster cpu's
and brilliant coding by some of the brains at discreet...... I remember
the day clearly."






small

Peter
Webb, who is credited as the world's first flame artist, started along
side Tregaskis in Melbourne. "I do remember when Gary showed me. He was
always excited to bring a new alpha build and would watch for the 'WOW'
reaction when he showed us new stuff like displacement with lighting.
The tracker was one of those moments. We had been matching plates by
hand which was insanely laborious and to see the software rapidly
chugging through the shot with that little red box locking on perfectly
was mind blowing. That was part of the wow factor. The rest was the
realization of how incredibly useful this feature was."





The first system used for film use was in 1992 when flame started work
in the feature film Super Mario Brothers. Super Mario did not make the
Oscar nominations, but it was included in the bake off that year. By
the end of 1992, Flame had moved into commerical work at Lamb and Co.
in Minneapolis, Minnesota.








1993





In 1993 Flame started to be noticed and Version 3 released.





The early hardware config required to run flame and its new trackers is:



  • Silicon graphics VGX 420
  • with multi-Buffer and FX option
  • 64 Megabytes of Memory
  • Standard High Density Tape Drive
  • 2Elite2 Fast SCSI-2 Drives with controller card
  • Videolab card
  • Abekas A66 Digital Disk Recorder
  • Wacom 3D312E Pressure Sensitive tablet











1994





In 1994 the first flame Siggraph users group meeting met in Orlando. V
3.9.10 was released and it was the last version for VGX graphics, from
then on Discreet supported the Onyx range of SGI computers. I/O was not
part of the inital product so early artists had to use an Abekas to
bring in and lay off to tape.





" I remember demoing the tracker myself in the early 90's at trade
shows and we always used this footage of some Russian soldiers
marching," Webb tells. "We would track the Russian emblem on their fur
hats and then replace it with a flame fish. The punters LOVED it as it
had never been seen before. Single point tracking first, there wasn't
any multi point tracking in the first version", he laughs, "the
reaction was always 'how the f**k are you doing that ?'"





Rodriguez remembers "that when we were making the decision to buy, we
had traveled to California to see the people from Colorgraphics about
Composium. I made a list of stuff that we liked and that I thought
should be on flame. Russell [ e: Russell Weaver, one of the original investors in discreet]
promised that if in one year all of this stuff wasn't in the system
they would refund us 110% of the cost of the system. I remember that
Gary used to travel from site to site, fixing site-specific things, and
configurations that might not be the same as at discreet. He would then
take his tar tape and go to the next site. They made their 1 year
deadline."





It would be several years before any other product would allow tracking
for VFX work. Webb also remembers " quantel coming out with some
tracking software sometime after discreet. Trying to pretend they had
thought of it years ago... Ah... The dog stab dog world of image
processing in those days... Now its all so samey and runs on my
laptop...if imitation is the sincerest form of flattery, Gary's tracker
should be blushing"






Tracking
was first shown on a Quantel Henry in 1994. The demo involved tracking
a Quantel logo onto an elephant. According to Quantel's Steve Owen,
"Some of the quantel team had worked on image tracking years earlier in
a lab but in a pure research capacity."





Colin Wrey did the first implementation - called ALF for Auto Lock
Follow. Wrey is one of Quantel's resident geniuses and is still at
Quantel working on the new generationQ product. "Once we decided to do
it the basics were simple - it took a couple of days for the first
implementation - the trick was to make it useable," remembers Wrey.
"There's a balance between a perfect track that takes forever and an
interactive track that falls off from time to time. We decided to go
with interactivity and the real thought went into making it easy to
use, making it easy to stop and restart a track because it was never
going to be perfect." Since the early days of development 4 point
tracking, the ability to track outside the picture area, offset track
for dealing with track points that are obscured for part of the path,
and graphical manipulation of tracking data were all added to the Henry
.





The iQ was first shown at IBC 2000. iQ (and eQ and gQ) have a
completely new tracker with up to 99 points, including on screen
manipulation of these points. At the moment, Quantel has no 3D camera
tracking.








1995





In 1995 there was a major advance in tracking as Discreet moved from
version 3 to version 4. At the second flame user group meeting, head of
development Terry made his famous quote now known by old timers as
simply "Terry's famous quote." "We will now always ship 90 days from
show," said Terry. In reality it was nearly 12 months before the new
software and new tracker would be released, but with it came a major
improvement in tracking. Behind a large part of that improvement was
Benoit Sevigny.





Visual effects Supervisor Sheena Duggal explains that, "the original
flame had a one point tracker,...seemed to work by doing some kind of
emboss between frames and required a point with maximum contrast. When
Discreet bought flame, the tracker was updated by Andre Le Blanc (one
of the original founders). At this point it became a 2 point tracker
and if I remember correctly you could track scale and rotation. Then a
year or two later Beniot made it even better."





"I do remember going to discreet and talking to the boys and Benoit"
says Emigh. "They were an amazing bunch...the way they thought this
stuff up as if it was a 'hey look what I fooled around with this
morning'.... I do remember tracking being one of the things that made
flame stand out above Q".





At this time Mike Hughes was in charge of R&D at Discreet. "Benoit
worked on just about everything, including Soft Edits, at one point or
another," says Hughes. "I was actually coding the early scratch track
audio alongside Benoit before I took over managing Flame. At the time
of the v3-4 transition, I'd estimate that there were about 15-20
developers working on the release, which included the video and s+w
people directly implicated."





Sevigny started programming Fourier transforms at the age of 11 and
spent more than 12 years optimising it before he was allowed to deploy
his solutions in Flame's tracker. After joining Discreet he was
initially assigned to working on OMF I/O and even though he was an
digital signal processing expert he designed Discreet's database file
format.





Inspired by mathmatical legend Jean-Baptiste Fourier and years of
writing real-time processing/analysis on a Commodore 64, Sevigny set to
dramatically improve the speed and accuracy of tracking. "The pre-4.0
Stabilizer was originally designed by Gary Tregaskis and was maintained
for a while by Andr? LeBlanc," says Sevigny. "It used a
least-mean-difference method implemented in a brute force manner using
the graphics hardware. Its original purpose was to stabilize unsteady
shots but the integration in Action as a general tracking tool really
allowed to make most of the technology. But the main problem was that
in the early days, tracking a 30 seconds spot was a half an hour batch
process that was not guaranteed to succeed. Although the idea of
providing a tracking tool in an online compositing system was at the
time revolutionary, it was prohibitive to lock down an Onyx-class
machine for this task and to supply coffee during the many breaks the
artist was forced to take in between retries."





"When," Sevigny remembers, "in a wild move, Michael Hughes offered me
to work on the tracker, the tool had a very basic UI and supported up
to four trackers when accessed through Action. I?m quite sure that at
the time, nobody expected me to transform the tool in such a radical
way." For the Flame 4.0 Stabilizer, discreet and Sevigny mainly wanted
to bring tracking to an interactive level, that is, on par with the
rest of the application. "In this respect, I think my most important
contribution is the design of the first widely available truly
interactive tracker and this gave Discreet?s products an edge over
others? for years to come" comments Sevigny. "This first tracker of my
own used a cross-correlation method using Fast Fourier Transforms
(FFTs). This method is indeed fast but is not in general fool-proof. To
help it in some circumstances, I provided two analysis modes: a
luminance and an edge mode. The luminance mode used a standard
cross-correlation while the edge mode relied on phase correlation. The
three colour channels were processed independently and the final match
was a combination of the three results".





In version 4.0, Discreet also introduced a parameter that allowed to
reject results that were below some correlation threshold, thus keeping
the tracker from being fooled by objects in the foreground. This was
demonstrated for the first time to ecstatic users at the 1995 NAB user
group meeting in the now famous Speed shot where a bus is tracked as it
passes under a bridge and momentarily out of site. At the time "it
really seemed like magic to us" jokes Webb.





Also new in 4.0 was the patented reference switch mechanism that
allowed to switch to another feature when the first one is occluded of
goes out of screen. Sevigny recalls, "One day, while I was working on
grain management at the London office, Sean Broughton from
Smoke?n?Mirrors came by and challenged to track a sequence he had a
hard time with (if I remember well, it was the Levi?s ?Planet? spot).
The shot, with an ever changing moving feature, could partially be
tracked with Fixed Reference on, but with the roaming reference mode,
the error would build up to an unacceptable level. The only workaround
was to track successive segments with different reference frames (in
fixed mode) and to try to stitch together the animation segments, which
is far from being an easy and accurate task. I then realized that when
the fixed reference mode is on, the reference should be updatable
on-demand (instead of continuously with fixed reference mode off). This
would give the highest accuracy while letting the user decide when the
reference should be updated. Thanks to Sean, the Snap function appeared
in the following release. To use it, simply back off the timeline just
before the tracker looses track and snap the reference. Then restart
the analysis from that point. Snaps are remembered in the reference
Channels, so reanalyzing the sequence will automatically make use of
them."








1996





Jerome Chen, Gary Jackemuk and Ron Brinkman gave a class at Siggraph on
compositing. From this Brinkman would go on to write the now definitive
reference book 'The Art and Science of Digital Compositing'. Brinkman,
formerly of Sony Pictures Imageworks already had a long string of
credits including In the Line of Fire, Die Hard: With a Vengeance, and
Speed . "After finishing up the work on Zemeckis' 'Contact' I decided
that it was a time to take a break from production and try something
different," says Brinkman. He become one of the original people behind
Shake and Nothing Real and is now at Apple. Shake -- originally planned
to be named IT (for Image tool) or even "Look" -- took the film world
by storm. This was primarily due to the fact that it worked in a higher
bit depth than anything else on the market, pushing past Inferno's 12
bit linear to floating point, yet also running on desktop machines.





"An early version of Shake (possibly before it was called that, and
possibly still in a prototype shape) was actually used on the opening
shot from Titanic," says Brinkman. "A deep underwater shot where
everything was a similar shade of ocean- blue. The shot originally been
started at 8 bits/channel of colour information but the subtle tonal
gradiations brought out tremendous banding problems. Shake was brought
in and its higher bit-depth capabilities were crucial to getting a
clean artifact free shot out the door".





Meanwhile, Discreet had not stopped working on tracking and at their
NAB 96 user group a new Flame 5.0 was previewed for the first time with
another complete overhaul of the algorithm. "While version 4.0 had set
the pace for the version to come, I was not totally happy with it. Some
people preferred the pre-4.0 because it was more forgiving. This is
why, after a digression working on grain management tools, I decided to
make a come back and revisit the whole approach." recalls Sevigny.
"This time, I wanted to fix some accuracy and robustness problems while
again improving on the speed. The definitive algorithm does not use
cross-correlation at all (although some people pretended it does). It
is more pre-4.0 like, but it still uses my beloved FFT implementation
to efficiently do the computation. This method is so robust that I
didn?t need to provide distinct modes for luminance and edges anymore,
so it worked out of the box. After extensive tests, I also realized
that trying to combine different results from three colour channels was
a source of instability, so I decided to merge the colour channels
upstream, thus making the tracker colour-blind as a side effect. It
proved to be more robust to illumination changes and required three
times less processing".





Rich Bobo, Senior Flame artist, then a demo artist for Discreet recalls
"Yes. Benoit was a clever, young, mad scientist type of programmer -
hopped up on espresso - and full of great ideas. I remember him showing
me all these tracking tests he was doing, using FFTs and other types of
pixel comparisons. He experimented with center weighting of pixel
grids, separate R, G and B tests, luminance weighting, etc. At one
point, there were a lot of individual controls that the user had to
play with - and, it was not very intuitive. His thought was that it
would be more flexible, to allow tracking in different situations.
However, small tweaks could have very different results and it was very
fiddly. I kind of gently suggested that what the user would want would
be a "one-button" solution that would "just work". He looked rather
dismayed but, to his great credit, he spent a ton of hours trying to
make an all-in-one version that would be a no brainer tracking
solution. In the end, he came up with exactly that - and, he made it
really, really fast! I recall him proudly stating that the tracking
algorithm could do analysis at 70 frames a second, if it didn't have to
wait to load individual frames from the disk array!"





Sevigny recalls "actually, I wanted from day one to provide a
"one-button" solution but it took some time before a I solve this
difficult problem.  Being a musician myself, I always thought that
ultimately artists should not have to fiddle with numerous and obscure
parameters to have to job done.  But when it's necessary because the
algorithm doesn't handle all cases, it's nice to have them.  Finally,
5.0 offered what I had in mind from the very beginning"





The idea behind the increase in speed was not about showcasing how much
faster than real-time the programmers can get, but in making more
demanding uses of tracking practical. Previous use of the tracker in
flame required either 1 tracker (stabilization), 2-3 trackers
(translation/rotation/scaling) or 4 trackers (corner pinning). In order
to tackle new applications like garbage mask and warper mesh tracking,
the new algorithm had to be lighting fast and had to support an
unlimited number of trackers. When tracking hundreds of features, the
slightest difference in speed is magnified a hundred fold. Another
important issue with speed was the advent of high resolution digital
film and HDTV around this time. With a larger-sized reference and
tracker area, much more processing was required.





"Tracking algorithm design being a black art (it?s nearly impossible to
make something that will work in all situations), I also wanted the
users to easily correct inaccuracies." says Sevigny. "For that matter,
I developed a totally new viewer in which you could edit motion paths
in context through a patented overlay which allows you to manual
register the reference frame to the current frame. Managing hundreds of
trackers can be a daunting task and I hope this new viewer made this
easier.








1997






Version
5.0 of Flame shipped in 1997. After version 5.0 of Flame, Sevigny left
Discreet and now works at Kaydara doing real-time character animation
including automated lip syncing. Around this time, Australian Steve
Roberts was moved to Canada. Roberts had been part of production
company NYPD in Crows Nest Sydney. Digital Fusion was a proprietary
compositing solution at the post facility Steve started in Sydney.
Shortly after some serious interest by Toronto based DPS, eyeon was
born and moved to Ontario, Canada in early 1997 where it is currently
based. Rony Soussan, was one of the first ever Digital Fusion users,
Rony Soussan, " I was one of the first customers to purchase Digital
Fusion and I can tell you that it has gone through quite a few changes.
It first appeared as a single point tracker, then eventually a 4 point
corner positioner. Soon after that we began building triangulation into
the tracker and we created a stabilizer version. Now, you can track as
many points as you want, have automatic triangulation, stabilization
(see tip below), corner tracking, perspective tracking, and you can
even embed a tracker into any animatible point or control within
Fusion. The accuracy has also become significantly better and faster. I
can quite honestly say without question it has become one of the best,
if not the best tracker in the industry".





Eyeon's Digital Fusion was for a time bundled with Alias. Eyeon did two
flavors of Maya Fusion for Alias. A light version shipped with all
versions of Maya for Windows. There was also Maya Fusion, which was
essentially the same as Digital Fusion except for having Maya marking
menus and looked the same as Maya. It stopped in Feb 2001 when Alias
consolidated its focus into Maya 3D. At the same time they stopped the
A|W Composer development as well






The
product was significant not only for providing 2D tracking tools to the
PC market and then evolving them into days powerful cross platform
tools with full floating point support and the world's first Open EXR
support. Alias also released Maya Live with the Maya Unlimited set.
Surprisingly, Maya Live was developed just down the road from NYPD in
Sydney's Crows Nest by post-production company Garner McLennan Design
(GMD). GMD eventually sold the software to SGI/Alias wavefront. Chris
Horbath, then in R&D at GMD and now at ILM, started work on a
software colour correction package. He needed a framework for it to
side within so he started developing Raindance, a product not unlike
Flame. As part of this basic work he started working on a colour window
tracker to allow colour corrections to track shapes in the image. He
then hit upon the idea of taking this technology and using it to
dynamically track and adjust two shots to align with each other. to do
this he needed to triangulate the camera. GMD's Rob Nicol and Simon
Brewster took the product to NAB 1996 and sold it to Alias, it appeared
first as a 2d tracker in composer but this was right when Alias was
merging with Wavefront and looking to introduce Maya, the 3D tracker
would appear as Maya Live a year later .








1998





1998 was the year tracking started to be acknowledged by the industry
awards. At the 1998 Oscars, the Scientific and Technical Academy Award
went to Gary Tregaskis for the primary design and to Dominique
Boisvert, Phillippe Panzini and Andre LeBlanc for the development and
implementation of the Flame and Inferno software





Also that year Dr. Douglas R. Roble won the technical Achievement Award
for his contribution to tracking technology and for the design and
implementation of the TRACK system for camera position calculation and
scene reconstruction. The TRACK system is an integrated software tool
at Digital Domain that uses computer-vision techniques to extract
critical 2D and 3D information about a scene and the camera used to
film it. Thaddeus Beier of Hammerhead won for the design and
implementation of ras_track, a system for 2D tracking, stabilization
and 3D camera and object tracking. Hammerhead productions was founded
in 1995 by Jamie Dixon, Thad Beier, Rebecca Marie and Dan Chuba -- all
ex-Pacific Data Images employees. PDI was then a ground breaking
effects house and the first company to invest in workstations over
massive main frames and had a vast history of impressive work. This was
before the Dreamworks buyout of PDI and its later Shrek fame.





imright(art_of_tracking/track_3De4.jpg)While Roble won the Technical
Achievement Award in 1998, the first version of TRACK had been
developed in 1993. TRACK, now in version 5, has been completely
rewritten and is still used today at Digital Domain. TRACK feeds
Digital Domain's (d2) NUKE compositing system with full 3D camera
solutions (Nuke would itself win a Technical Achievement Award 3 years
later in 2001). Roble is the first to admit that tracking is still
"very much an art". He sees the role of his team which includes John
Flynn and Henrik Falt as providing the artists at Digital Domain with a
range of tools that allows them to solve very complex problems. He
explains that artists are often required to start with one method, then
use another and finally a third or fourth approach to solve many of the
more complex problems they face. TRACK is therefore a very flexible
tool allowing a number of different ways to track and solve a camera
move. The software has moved from its roots as a 2D tracker to now
encompassing Optical Flow and a highly complex 3D camera tracker.





The move of TRACK from 2D to 3D tracking was reflected by a general
shift in the industry to 3D. Just the year before in 1997,
Science-D-Visions in Dortmund, Germany became the first software vendor
to release a reliable survey-free 3D camera-tracking application. Since
then, 3D-Equalizer has become one of the key matchmoving systems of
choice for the digital media industry.





In early 1998 REALVIZ was founded with the goal of commercializing
products based on over ten years of computer vision and robotics
research by INRIA, the French National Institute for Research in
Computer Science and Control. The company founders are former
executives from Medialab, a subsidiary of the French TV channel ?Canal
+?, and former research scientists from INRIA.








2000





REALVIZ successfully launched their first four applications
ImageModeler, ReTimer, Stitcher and MatchMover by the year 2000. These
were part of the next generation of tracking programs -- those that
aimed to solve 3D tracks and produce an exact camera move in 3D space
that could be used by 3D and 2D programs alike. By the start of the new
millennium, tracking R&D battles had moved from the big iron boxes
of Henry and Inferno to dedicated PC programs harnessing the power of
the desktop and the latest in University R&D.





?The main benefit from matchmoving software,? says Luc Robert , Chief
Technology Officer at REALVIZ, ?is a marked increase in productivity.
Automatic matchmoving is definitely a huge help in this respect, since
on a significant fraction of shots it produces a solution which
requires no human interaction at all. Most post-production companies
using automatic matchmoving have integrated it into their pipeline so
that, for virtually no overhead cost, they can benefit from these
automatic solutions. Despite this, there will always be shots which
automatic matchmoving software will not be able to solve (the extreme
case being where there is absolutely no element visible in the footage
on which the tracking algorithms can rely). It is crucial for
professionals to solve 100% of the shots they want to matchmove, and
for that, the software has to allow them to control and guide the
process if necessary.? REALVIZ proved very successful over the next 4
years, MatchMover technology has been used to create visual effects in
films such as 'Troy' , 'The Last Samurai', 'Hellboy', 'Daredevil'
'Dinotopia' and Harry Potter






The
battle for technological leadership would be fought by REALVIZ, 2d3's
boujou and the innovations at Science .D. Visions in Germany with their
3D-Equalizer software, who would themselves win a Technical Achievement
Award in 2001 for for the development of "3D-Equalizer , an advanced
and robust camera and object match-moving system." which in the words
of the Academy, "this commercial tracking system provides "survey-free"
tracking, which significantly reduces the need for painstaking,
error-prone measurements on sets."





3D-Equalizer's feature film credits are impressive. Lord of the Rings
(all three), I, Robot, X-men 2, Spiderman, Gladiator, MI-2 and many
others including the Emmy Award winning Walking with Dinosaurs. At the
end of 2000, 3D-Equalizer maintained a technical lead in the industry
with such innovations as solving footage using zoom lens and allowing
secondary images to be used to help find a solution. In 2001, 2d3's
boujou was released.








2001 - 2002





boujou was launched at NAB 2001, using advanced adaptive algorithms
developed from vision science research. The software greatly simplified
what was achievable by normal 3D professionals and the product took
off. So much so that in various markets the product name became a verb.
"We'll boujou it" was heard on sets and in studios all over the world






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boujou
has made a major contribution to high-profile television and film
productions, music videos and commercials by facilitating the creation
of visual effects that seamlessly combine live action and 3D. In 2002,
2d3 was awarded with a Primetime Emmy Engineering Award for boujou.
2d3, based in Oxford, is a wholly-owned subsidiary of OMG plc which
also owns Vicon Motion Systems, developers extremely advanced motion
capture systems. boujou has been used on such films as The Matrix
series, Harry Potter, Lord of the Rings and Troy. Playing on their
strengths, 2d3 released boujou bullet in 2004 - an even simplier
version of their boujou two software. Bullet offers all the
functionality of version two with a new built in 'wizard' feature, all
for a fraction of the price of the full version. Version three of the
main product will ship in September 2004 with new features such as
solving zoom lens and a new automatic radical distoriton model. Lens
distortion is a major issue for tracking programs, but according to
2d3's Steve Hill, "We're going to supply a Shake node with boujou3 that
will allow you to use the boujou lens distortion model to add or remove
distortion " Shake already has a distort and most importantly - invert
distort function, but the new plugin for shake is a special lens
distortion node. Shake distortion nodes are extremely important to many
pipelines, REALVIZ's Liz Tjostolvsen points out that by the end of
September 2002, MatchMakerPro 2.5 was released with just such a Shake
distortion node.








2003






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Today,
new products appear regularly and prices have fallen. Oscar nominated
Visual Effects Supervisor Nathan McGuinness joked at a recent AEAF
conference that Asylum used a whole range of tracking tools on the
incredible task of tracking ships and oceans for the film Master and
Commander. This included Andersson Technologies SynthEyes 3-D tracker
which retails for only US$349. Andersson Technologies LLC was founded
by Russ Andersson in August 2003 to commercialize SynthEyes. Andersson
had previously been at Bell Labs for 15years and also wrote SceneGenie.
SynthEyes was first marketed in December 2003, at which time it had
already been used by beta testers in feature films such as Bad Boys 2,
Charlie's Angels 2, and Master and Commander: Far Side of the World. It
is an amazing price point but also very fast. Andersson comments that
"it has been designed from the ground up to be fast. There are a
variety of techniques used internally to make this happen. Sometimes a
bit of planning can save quite a lot of time, even for a computer! " He
later jokes "I have a background in robotics and real-time computer
vision, where speed is the norm.".





Another interesting product came from the public domain. PFTrack was
developed using a licensed technology base from a product called
Icarus. Product Director, Mike lancaster came across Icarus while
looking for key technology to incorporate into Pixel Farm's as yet
un-announced long term strategy. The Pixel Farm approached AIG and
quickly negotiated an exclusive license deal to utilize technology from
Icarus because the support and management of the software was causing
untold problems for AIG. Icarus was distributed free to non-commercial
sites, with a commercial license available for use within professional
facilities. According to Lancaster, "you can count on 1 hand the number
of commercial licenses sold, yet there were some very big names on the
IP listing which was testament to the quality of the product.". In many
respects, The Pixel Farm saved Icarus, developing a fully professional
application from the base technology. The Pixel Farm has created a
complex analysis tool capable of far more than just match moving
designed around complex long form projects. To address the match move
market, The Pixel Farm spun off PFMatch as a low cost desktop
application with a full set of camera tracking tools but lacking the
high end tools such as batch processing, proxy resolution handling and
application plug-in support found in PFTrack.





The world's leading desktop effects solution, After Effects (AE) from
Adobe, also includes a new tracker. AE has placed the technology in
more hands than perhaps any other single product, providing a huge
group of people the chance to use tracking daily. While AE does not do
3D tracking, Adobe's After Effects Michael Coleman, comments "that
Boujou has a plug-in for importing their data to After Effects. Also,
AE can import camera data from Maya .ma files, so any 3D tracker that
can create a .ma file can apply the 3D camera data to an AE camera. AE
can also extract camera data embedded in RLA sequences, which is of use
to certain 3d people." AE has advanced 4 point tracking that is both
impressive and very useful. "An advanced capability of our perspective
corner pin tracker is it's ability to apply the surface to a different
surface than was tracked," Coleman states. "In other words, if you
track four points on a wall, you can correctly corner pin something to
the floor plane, regardless of what's on the floor".





AE was initially not incredibly fast at tracking but Adobe has done a
lot of work in speeding it up. "We have put significant effort into the
tracker over the past two releases." explains Coleman. "The list of
improvements is long, but top of the list must be accuracy and speed.
It can be 20-50 times faster in some cases. All of the track data is
fully integrated into the AE project and available on the timeline for
parenting, expressions, or simply copy and pasting tracker keyframes
between layers. Users have reported excellent accuracy results
recently, particularly with After Effects 6.5. Also new to 6.5 are is
one-dimensional tracking, 2-point scale tracking, zooming the track
point when you are dragging it, and showing the motion path for the
resulting track data."







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Tips and Application Overview












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2D Tracking



In looking at what tracks and how it is important to understand one key
point, most modern trackers with the exception of Digital Fusion (and
to a lesser degree Shake and AE) have all moved away from colour
processing approaches. Almost all trackers are now biased to a
luminance of black and white version of the track box. Digital Fusion
alone amongst the leading packages uses colour information
automatically. When a track is performed in Digital Fusion, the user
interface shows the stength of each of the three colour channels and
then which it has decided to use.



Digital Fusion also has another very innovative feature. While most 2D
trackers also do corner pinning and 4 point tracking, DF offers a
weighted solution. If you need to track a large object but not just one
individual point on it and the object motion causes problems (such as
tracking any object floating on water), DF allows several points to
contribute to one solution. So even though an an individual point may
have tracking errors due to perspective change, the overall movement of
the object can be tracked from mulitple points and combined to provide
one single track solution.



Shake also offers the ability to use hue or saturation for tracking
instead of luminance. Ron Brinkman, author of 'The Art and Science of
Digital Compositing', points out that in some cases of multicoloured
patterns this can be very effective. While most tracks are correctly
done using the normal tracker, if a monochrome version of your image
has poor contrast, try a hue track. Adobe's Michael Coleman notes that
"After Effects uses luminance as the preferred color channel for the
track, but there is a user control to switch to RGB or saturation. In
practice, most hand-made tracking markers work best using luminance".



Tracking now exists in every aspect of visual effects and is moving
into colour grading. Discreet's Lustre has tracking and Quantel's
QColor integrates into eQ and iQ to give multi-layer non-linear
in-context color correction. Both applications bring effects tools to
the colorist, which is something traditional color correctors haven't
offered.





What is the ideal tracking marker to use on set?



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We
asked this question of almost every software supplier and technical
expert. Their replies and tips may surprise you. "Well, for a start
make sure your tracking markers don't blow away", jokes Quantel's Steve
Owen. "Framestore (has) a lovely story about a money shot in Walking
with Dinosaurs. It was a helicopter fly past and they would have to
comp in the 3d dinosaurs walking off towards their eventual extinction.
They used baseballs as markers but unfortunately overlooked the down
draught from the helicopter which promptly moved all the markers
around. It was fixed with great skill in post."



The common trackers are crosses, crash test dummy crosses in a circle,
triangles or circles. The jury is out between the various experts,
perhaps due to each product having a different algorithm. Coleman
mentions that "AE doesn't really prefer one object shape over another.
I've always been pleased with results of using the cross or the dot,
but this is probably personal more than technical. From a technical
point of view, the AE matching algorithm has a technique for
discovering the shape of the target. I believe that this technique is
based off of the center of the feature region. This means that there is
a benefit to putting the center of the feature region directly over the
middle of the mark."



The issue of which tracker is best is also effected by what the camera
is doing - large dots zooming away to small pin points can be a
problem, camera rotation, motion blur and depth of field can also be
big factors. "Strictly speaking, a simple circle provides more robust
tracking since it is rotation invariant ? the tracking point remains
the same even if there is rotation in the shot," says Discreet's Marcus
Schioler. "Usually, losing a track occurs when the tracked shape
changes or the lighting conditions change. Eliminating rotation
variance is, therefore, a big plus. A circle also tracks better with
zoom and focus changes. Curious Software's David Franklin agrees. "The
most important thing is that the shape of the tracking marker doesn't
change significantly during the motion. You want to minimise the
alterations caused by rotation, perspective changes etc.," says
Franklin. "Therefore, I would say that a simple sphere or circle is
best." Digital Fusion's Rony Soussan comments "let's just say that
there is no right or wrong answer, it all really depends on many
factors. How close or far are the trackers, is the camera doing a dolly
or pan? ..I've done music video's where we had nothing but gaffer tape
and we tracked it perfectly. It's less about the tape or circle or
square than it is about the artist driving the tracking software.
Nothing's automatic regardless off what people say. That being said,
I've had a lot of success with a triangle myself, there a pattern
that's stronger then a circle so the tracker does have angles to track
for scale as the marker changes size."



A few years ago LED trackers appeared to be in vogue, but most of our
experts agree LEDs do not make for better trackers, except in low light
conditions "Providing the marker that you're using makes a good
contrast with the image, I wouldn't expect LED to be better," states
Franklin. "Obviously the LED should have very good contrast, but I
would be worried that glare/blooming from the LED would end up on the
plates, making it harder to get a good result." DF's Soussan agrees and
notes that he's " found that glowing or illuminated objects can give
undesired results to the camera lens, like glowing and focus issues"
However, Discreet's Schioler points out that "using an LED marker could
be a big help in some tough lighting conditions as the marker would
remain visible even under dark shadows."



While it is ideal to have contrast due to the fact that most trackers
are monochrome, most experts agree there is little point in running
special colour corrections. The tracking algorithms generally already
have some sort of color correction or contrast stretching built-in. Ron
Brinkman points out "there is nothing much you can do that the internal
algorithms of Shake's tracker can't also do". In fact, color correction
done by an artist could have negative impact on the track by increasing
the signal-to-noise ratio and interfering with tracking, says
Discreets's Schioler.



Dealing with Noise in Tracks



" (Noise....) there lies the art of tracking, " jokes Digital Fusion's
Schioler. Fighting noise by reducing jitter or providing a cleaner
track is a key aspect of doing successful tracks, especially in 4 point
camera tracks. Tracks in their basic form can simply be edited by hand
to remove spikes or errors. "Our tracker produces standard motion paths
which can be used and edited anywhere in gFx" says Franklin. "You can
remove jitter by deleting keyframes and allowing the curve interpolator
to fill in the gaps, but we don't currently have any specific tools in
the tracker for removing jitter. We are adding these though." Discreet
already has a jitter removal option, introduced with version 4 of the
software.



Most of the software experts we spoke with suggest experimenting with
some presoftening of the clip prior to tracking. A small blur could
reduce noise while maintaining the important image information for
tracking. "AE can reduce noise and jitter in the track data using our
"smoother" palette, which does just what it says," according to
Coleman. The AE expression engine can also be used to filter the track
data. Curious Software's Franklin has "found presoftening will often
help with motion blur - the tracker will tend to follow the 'center of
mass' if there's some amount of blurring."



Soussan aids the following suggestions for reducing noise, "One of the
ways you can do it in Fusion, is simple to reduce points. Once you've
tracked in Fusion it basically becomes a path that the tracker reads.
All paths, and shapes in fusion, including effects mask, curves in your
spline editor and the track data can be smoothed down using our reduce
points system. It will average the shape of the track down as far as
you want to push it until it's a smooth spline curve. Another way is to
de-grain an image prior to tracking, then replace back the original
footage, I'm sure you've heard that one before. Our tracker has option
based on sub-pixel accuracy that help compensate for noise, the default
settings work great, but if you need to really fight the grain then
bumping up the sub-pixel accuracy is definitely the way to go."



PFTrack actually has a very comprehensive noise reduction algorithm
called de-noise for noise reduction. These are specially designed
algorithms that act similar to a median filter but maintain all edge
detail. In essence they can be likened to high quality grain reduction
tools.



Some trackers respond to image size. For example, some 3D trackers will
produce a better camera track for film resolution material by actually
tracking a video size resolution image instead. This is not so in 2D,
says Discreet's Schioler. "There is no reason to scale down the image.
Under most circumstances, you should simply use larger tracker boxes.
Image resolution doesn't really change anything as far as motion blur
is concerned. The important thing here is tracker box size."





3D Tracking



Author Steven D. Katz, in the November 2001 issue of Millimeter,
explains perhaps better than anyone how 3D tracking works. Match
moving, optics, photogrammetry, and perspective drawing are all part of
an area of mathematics called projective geometry. Applied to various
spatial problems, it can provide solutions for measuring objects at a
distance, locating objects in space, and extracting 3D models from
photographs. Projective geometry has been used since the dawn of cinema
in the form of glass matte paintings and false perspective sets. Camera
angle projection, which is the process of extracting a perspective view
from architectural plans and elevations, was the standard method used
to visualize specific camera angles and views based on blueprints of a
set.



Katz explains that "camera-matching software utilizes a subset of
projective geometry called epipolar geometry. This branch of
mathematics is used to describe the geometric relationship between two
optical systems viewing the same subject and can be used to locate
points in space. Because a moving camera offers a new view every frame,
epipolar geometry works for a single moving camera as well, and each
new view is understood as a separate optical system."



The goal of a 3D tracking program is to solve the camera position by
using two camera views. "Think triangulation," writes Katz. Epipolar
geometry is a type of triangulation. When using photographs to
determine the position of a point on an object using triangulation,
it's necessary to match the image location point in one image to the
image location point in a second image. Matching these pair of points
in two images is called correspondence. Finding these matches would
appear to require searching the entire image. Epipolar geometry
proposes that the point we are interested is actually constrained to a
single line. This greatly limits the search for that point." By using
the path of the point to define a line, one can predict where a point
is going and greatly reduce the amount of computation and hence speed
up the tracking process.





What is the ideal tracking marker to use on set for 3D Tracking?



Like 2D trackers, 3D trackers rarely if ever use colour information.
"Chroma is relatively unimportant to boujou's feature tracker," says
2d3's Steve Hill. "Pre-processing the images rarely improves the
tracking results and we generally discourage pre-processing of any kind
because of the many adverse effects that it cause. The exceptions are
reducing the image size to reduce the effects of motion blur, and
tweaking the linearisation settings of very dark cineon images to bring
out more detail in the shadows."



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Unlike
the 2D experts we spoke with, the 3D experts have very strong opinions
on what will track best and provide a large number of innovative tips
on how to improve obtaining 3D camera solutions. Perhaps the most
definitve comments on trackers comes from 2d3's Hill who strongly
advocates triangular trackers. "The advantage to the triangle in the
circle is that it gives you three well-spaced, high contrast corners
for boujou's automatic tracker to pick up. The crash test marker has a
high contrast area in the centre, and lower contrast areas around the
edge. When this marker gets small and pixelated the central region
starts to give four noisy tracks instead of one stable one (the
detected features get pushed away from the corners by the blurring of
the image at lower scales). The triangle in the circle works much
better throughout a wider range of scales. Boujou's target tracker
works well on both sorts of marker, but for best results place the
crosshairs of your keyframes in the centre of an area of black or white
rather than at a corner."



Digital Domain's Doug Noble points out that their approach is very much
that of modelling the environment from a highly accurate recording of
on-set measurements. They aim to not so much give the 3D artist a
camera track set of data points, but rather to "track the room to the
camera" so the artist has a set with the camera moving through it.
Noble's TRACK software now usese optical flow and a range of solutions
including Laser scans or "poor man's LIDAR" (LIght Detection And
Ranging).



3D tracking falls into two classes, automatic trackers and manual
trackers. Many programs do both. Sci-d-vis' Rolf Schneider, notes that
"3D Equalizer has 3 different (manual) tracking modes: pattern, marker
and edge/corner. The marker tracking mode is specialized on unicolored,
flat discs placed on an unicolored background. 3D Equalizer computes
the 'center of mass' of the disc which becomes the tracking point, on a
frame by frame basis. That means that no previous frames are needed
during the tracking process so no error accumulation happens. Marker
tracking is very precise, but specialized. The cross/cheque patterns
can be tracked quite well by regular 'pattern' trackers, that's the
reason why people like to use them."





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3D
trackers normally require a set of 8 to 11 points to be valid at any
one time, but the same points do not need to remain valid for the
entire clip. Unlike 2D tracking, automatic point generation is common
in 3D tracking. This allows 3D camera tracks to solve seemingly
impossible tracks. Perhaps the one of the most impressive and difficult
tracks is to track helicopter moves over vast featureless oceans. This
is extremely tricky as Hill explains, "Tracking water is always a
gamble - if the sea is too rough then boujou won't be able to find
enough consistent tracks." That being said, results can be outstanding
as evidenced by the fact that Boujou has been used to track water
movies such as 'Enemy at the Gates' (Double Negative) and 'Troy'
(Framestore-CFC and MPC).





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Tom
King, 3D artist at Digital Pictures in Sydney comments that he finds
that Maya? Live will still track some scenes other automatic trackers
can't. He also feels it can also give more accurate Z depth than other
packages at times. Maya? Live, like some 2D trackers such as Digital
Fusion, show percentage confidence levels for the trackers in the UI.
King suggests the following tips for Maya? Live:


  • Mmake sure tracking confidence is 70 to 80 percent green
    for all points. Bi-directional tracking can be repeated from a lower
    confidence area that looks right in the point centred window. Repeating
    this will result in longer high confidence sections.

  • Delete keyframes for sections that deteriorate into yellow and red confidence levels.

  • Using
    smart update behaviour in the options section can improve the chances
    of good tracks with points that change shape through rotation or
    lighting.

  • Make sure the Ready to solve graph is all green for the frames you want to track.

  • Before
    solving, point blast all point tracks to check for mistakes that are
    not detected by the tracker. One of these can completely ruin the Solve.

  • Do
    the solving in the manual stages and look at the pixel slip numbers as
    you go. If you aren't getting a good solve, pointblast the tracking
    points again and correct any wandering points.







Dealing with Lens Distortion



One major consideration with 3D camera tracking is lens distortion.
Lens distortion generally has very little influence on the 2D tracking
process. However, it can have a substantial influence on the 3D camera
calculation process. For this reason it is wise to film a grid with
each prime lens (or in worse case film a known angular shape like a
building). Most 3D camera packages have tools to adjust for lens
distortion. For instance, 3DE includes a special lens distortion tool
called "warpdistort". It allows the user to remove and apply lens
distortion to image sequences and can be useful throughout the entire
production pipeline.



Lens distortion only affects the camera solving, not the pattern
tracking itself. REALVIZ MatchMover experts Luc Robert and Ronald
Mallet comment, "In MatchMover, lens distortion is represented by a
mathematical model, whose parameters are computed automatically based
on the point tracks. This model handles most of the lenses with a high
level of accuracy. MatchMover also exports distortion nodes to Shake.
In some cases, in particular when dealing with high-res footage, lens
distortion effects are too important and too complex to be represented
by a simple mathematical model. In this case, distortion can be learnt
using a calibration pattern, and images warped before tracking to work
on distortion-free footage. Later this year, we will provide specific
tools to perform this." 2d3's new verison of boujou handles lens
distortion but according to Hill, many facilities prefer to take
distortion out of the footage using Shake, Inferno or other products
before giving it to boujou. "If you go down this route," Hill states,
"you should make sure you use the right pixel aspect ratio for the
custom camera that you will have to create in boujou. We're going to
supply a Shake node with boujou3 that will allow you to use the boujou
lens distortion model to add or remove distortion. ". Pixel Farm, which
also produces a Shake, Digital Fusion and AE plugin, can deal with high
and low order radial distortions as well as distortions that change
over a number of frames.



Many operators fear trying to solve a 3D camera move that has had a
static resize in telecine. While a wider or larger picture will perhaps
allow tracking markers to be valid longer before moving off screen,
static resizes in telecine are not as disastrous as sometimes thought.
Hill explains that while an accurate film back is important, it is not
"as important as the pixel aspect ratio. If you get the filmback wrong
then you're going to get an inaccurate focal length value, but this is
rarely a major problem unless the value calculated is way out. Pixel
aspect ratio, on the other hand, can kill a camera track. It acts like
a kind of 1D lens distortion and will have a very big effect on
tracking accuracy. If the telecine process puts any squeeze on the
frames then you're in trouble". If the image is adjujsted in telecine,
it is important to know where the principal point (the projection of
the camera optical center on the film back) lies in the image. With
cropped footage, "it can even lie outside of the image," jokes the
RealViz team. "An error of a few pixels on the principal point will
generally not affect the tracking too badly. Knowing the value of the
camera focal length is helpful, both for accuracy and speed.
Measurements on the set are also helpful. Any such measurement can be
used by MatchMover to find a quicker and more accurate solution."



The more powerful 3D packages also allow for additional information or
images to be added to the solution. 3D-Equalizer allows stills to be
added, perhaps taken by a digital camera from the side of set.
MatchMover allows stills as well as data issued from ImageModeler.
"This is particularly useful when dealing with multiple shots of the
same scene, because it guarantees that all the solves are compatible
and part of the same 3D world coordinate system. It also makes tracking
a breeze," they point out.







































3D-Equalizer points out that all points should not be on the same
plane, the 3D solver needs different z depth, this is a problem when
markers are placed on a back blue screen.

Here the problem is solved as - while the points are all on the same plane- they are different distances from the camera



Here the issue is addressed by shooting at an angle to the blue screen wall.



The future of 3D tracking will most likely be linked to optical flow
technology. In optical flow solutions, every point is tracked and it
produces a set of floating point data which can then be combined with
traditional 3D tracking for far reaching solutions. One of the leading
companies in this new field is England's PixelFarm, who appear to be
leading the pack in multiple application uses of a core data solution.
The 2D features are used to calculate the 3D match move, and those same
2D features can also be used to calculate the optical flow. This gives
a very reliable solution to the optical flow calculation. PixelFarm's
Michael Lancaster points out that they "can also use 'user features'
(manually tracked points) to guide the flow computation. So for
instance, with old problem of a hand passing a face, stick a couple of
user features on the hand and you'll create a very much improved flow
calculation. You can also use splines (mattes) in a similar way or in
combination to define edges." The problem PixelFarm address is a common
issue for other tracking programs. 3D tracking is really a camera
solution, it is not fundamentally about tracking things in the scene.
In factm programs such as boujou provide matte generation to hold out
moving objects that will interfere with the camera track. While
programs such as 3D-Equalizer can be used to track people's faces or
hands, it is not their primary purpose. PixelFarm is building out from
a core of tracking data to provide object tracking (including motion
capture), camera tracking, motion blur analysis and even 3D scene
reconstruction.



Prices Coming Down, Quality and Features Up



The other trend moving forward is dramatic price reduction. REALVIZ has
introduced their 'Absolu' scheme in June of this year. 'Absolu' is a
new monthly subscription scheme, which enables users who require
occasional matchmoving facilities, to access MatchMover Pro regardless
of their size or budget. PixelFarm has introduced PFMatch at only 600
pounds (approx $1000US). 2d3 released boujou bullet, a much cheaper
'wizard-based" product with nearly all the functionality of the much
more expensive boujou2. Andersson Technologies is selling SynthEyes for
only $349US.



The price reductions are deceiving, because there is still an amazing
range of functionality. One particularly difficult problem for 3D
camera trackers are zoom lenses. While boujou users are waiting until
September for zoom lens solving tools in boujou 3, other packages such
as 3D-Equalizer, SynthEyes and PFTrack already include it. Shots taken
from a tripod do not permit a full 3D solution, but SynthEyes can solve
them to determine the pan, tilt, and field of view of the camera.
SynthEyes also determines the 3D direction to each tracker, resulting
in a spherical shell of trackers (panning, tilting, and zooming)
surrounding the camera within the user's 3D package. 3D elements can be
inserted into this environment more easily than using a small number of
independent trackers in a conventional 2D compositing application. But
perhaps SynthEyes' most amazing feature is its speed. Just as Benoit
Sevigny did at Discreet years before, Andersson has focused on solution
speed as a key enabling aspect of tracking and has been designed from
the ground up to be fast.





"There's no doubt in my mind that tracking will continue to evolve in a
direction that relies on characterizing the entire image as much as
possible, as opposed to specific feature-based analysis," says Ron
Brinkman. "Ultimately if your starting point includes information about
the camera (derived from 3D analysis) then any additional tracking
methods will have their accuracy improved dramatically."





Summary of 2D Tracking Tools



Adobe



After Effects has recently improved its 2D trackers and provides a
great set of standard 4 point tracking. While perhaps not quite as
powerful as some of the bigger boxes, it remains one of the most-widely
used effects solutions in the world.





Avid



Avid is the 800-pound gorilla of highend nonlinear video editing. In
the area of effects products their tools are now headed by Avid|DS. Its
Avid|DS and Nitro visual effects tools allow advanced compositing and
tracking. DS Nitris is a standard and high definition finishing tool
which offers power similar to After Effects and Photoshop. Nitro has a
powerful 3D DVE, vector paint, motion tracking, keying, compositing,
title and Symphony-like color correction tools. Nitro has come a long
way since its relatively helpless title tool in the original Media
Composer, but Avid still lags in marketing to the effects community.
For example, Avid was the only equipment supplier who declined to
contribute to this story.





Discreet - Advanced Systems



Discreet's Advanced Systems, which include Flint, Flame, Inferno, Fire,
and Smoke, all have 2D tracking. inferno and flame have 3D tracking.
The Discreeet trackers are fast and very powerful and only lack
multi-point solutions. Version 6 of inferno and flame contain an
updated 3D tracker with much improved algorithims as well as
auto-tracking. The lack of Maya export and a reliance on fbx as an
interchange format is annoying and buggy. The 2D trackers are still the
benchmark which other 2D trackers are compared to.





Discreet - Desktop



In 1997, Discreet aquired Paint and Effect from Denim Software. Paint
offered a vector based painting and cloning system for Mac and PC,
while Effect offered compositing capabilities. Discreet redesigned the
interfaces to make the applications more Discreet like, and merged the
two applications into Combustion. Along the way, they also replaced
some of the core functionality such as Keying, Color Correction, and
Tracking with the same tool set found in Discreet's Advanced Systems.
This provided flame-level tracking at a much much lower price.
Combustion tracking files can be opened directly in the larger
inferno/flame/flint/smoke/fire products.





Curious gFx Pro

gFx is a relatively new product for Mac OSX and Windows. Unlike other
paint programs it is designed around a stong user interface that fully
embraces moving footage, as such it can import, composite, track, or
stablise footage easily. One of Curious's founders is the man behind
Parallax and Matador, which developed tracking on a PC back in 1995,
and it shows in some of the depth of tools already available in the
software.





Digital Fusion



Digital Fusion started in Sydney and moved to Toronto, Canada. At one
stage, a version of Fusion was provided with Alias 3D. Today, eyeon has
gained one of the strongest postions in NT/Windows desktop compositing
solutions. Eyeon has two main products: Digital Fusion and DFX +. Since
Shake's move away from NT/Windows Digital Fusion has provided a
powerful cost effective solution.



Digital Fusion 4 is eyeon's flagship product and marks the ninth major
release of this powerful compositor. DFX+ 4 is the 8-bit expandable
version of eyeon?s image processing software, Digital Fusion. DFX+ is
based on the architecture of DF4 and offers a number of significant
enhancements to its predecessor, DFX, including the flexible flow,
superior character generation, PSD import into separate layers for
animation, and more. Digital Fusions's 2D trackers are some of the most
advanced, and well integrated into every part of the product.









Bauhaus was founded in 2003. Bauhaus Mirage is a unified environment
that simplifies the creation of animated graphics and special effects,
including cartoon style animation in a 2 1/2 D environment. It features
combined real-time video paint, animation, and effects functionality.
Mirage runs on Microsoft WinXP/Win 2000 and Apple OS/X. Mirage version
1.2 followed version 1.01 for the PC, and was the first full OSX
version. There have been some relatively small (hidden) changes in the
tracking function with a view to smoother paths. Mirage's tracker can
work in a RGBA, or consider just single color channel, as well as
either Luma or Saturation. Mirage's tracker panel provides a monochrome
magnified image of the the tracking area, along with a channel menu.
This can be useful to visually judge which channel is optimal for
tracking pruposes in a given situation.







Quantel





The Quantel product range consists of the, iQ DI, eQ post, and gQ
broadcast graphics. All share the same code base and toolset including
tracking. Quantel has made great advances in recent years in digital
intermediate grading. Quantel has no 3D tracking but a comprehensive
set of 2D tools in all products.









Shake



Apple's
Shake has a powerful set of 2D tracking software, but unlike some other
compositing packages, Shake is only a 2D compositing package without a
3D camera view on the composite. Given Shake's popularity this has
caused many of the other specialist products to code special 2D export
functions especially for Shake. This allows 3D tracking of complex
camera moves and exporting special Shake data for tasks such as 4 point
camera tracking.







Summary of 3D Tracking Tools







3D-Equalizer



One of the original 3D tracking tools, 3D-Equalizer is both highly
powerful and widely used. 3D-Equalizer is not aimed at the dv pro
consumer market. It is very much a high end feature film or major
production tool. As such it has a serious learning curve but the web
site has one of the most comphensive interactive teaching aids
available of any company. The more data (focal length, survey points)
which is recorded on set, the more information can be fed into
3D-Equalizer. This helps to reconstruct proper camera moves. Problems
can arise when these data are wrong because of "human error".
3D-Equalizer becomes confusedand it is difficult to debug by the user
3D-Equalizer is now avaliable for OSX and NT.







boujou and boujou bullet



Due to its relatively simple user interface and low stress operation,
boujou has a very wide acceptance. boujou will track many things better
than most, but until version 3 it will lack zoom lenses and some of the
secondary camera footage options found in other applications. boujou
bullet is even more user friendly. boujou and boujou bullet run on both
NT and OSX.







monet



Monet is a 4 point tracker that actually uses planes rather than corner
points. Properties of the source material such as lens distortion,
shadows, highlights and grain/noise can be automatically applied to the
new element. Combined with options for per-pixel motion blur, focus
blur and colour adjustment controls makes Monet an extemely power
specialist application. Monet was developed specifically for Cinesite
in London for tracking the 2D animated paintings into the picture
frames in Harry Potter III. Monet run on Windows, Linux and OSX.







REALVIZ MatchMover

REALVIZ is an outstanding company with a wide range of tools and there
is a strong relationship between the technology embedded in all the
REALVIZ products. For instance, MatchMover, ImageModeler and Stitcher
share estimation algorithms that compute point and camera parameters
based on correspondences across images. ReTimer is a little different
since there is no 3D involved in the estimation process.



MatchMover has had a very powerful and flexible engine. It computes
varying zoom as well as distortion and handles multiple shots and
secondary helper pictures. The product incorporates both completely
automatic tracking and supervised tracking, without limit in combining
both approches. MatchMover can be adapted to any shooting situation:
availability or not of survey data, information on camera lens, set
constraints, motion control data, camera motion constraints (rail,
tripod, fixed camera), different sequences from multiple viewpoints, 3D
model-based tracking. Whatever data is available, you can take
advantage of it within MatchMaker Pro. This versatility also extends to
pricing through the Absolu pricing scheme.

Image courtesy of Jeff Mottle ? CGarchitect.com









ras_track



Hammerhead sells their award winning tracking software directly. While
numerous licences have been sold, it is not widely used in comparison
to other leading packages. ras_track only runs on NT there are no plans
for an OSX version.





TRACK



Digital Domain's Academy award winning tracking program, now at version
5. TRACK is not yet available commercially outside Digital Domain, but
Digital Domain has established a software division called D2 software
to commericalise Nuke, Digital Domain's compositing program. Nuke
provides compehensive 2D tracking and stablisation.







The PixelFarm



The PixelFarm is a very exciting company, pushing perhaps faster than
anyone else. The PixelFarm's PFTrack is at the core of The PixelFarm's
data centric workflow. No longer purely a match move application,
PFTrack is a means to extract complex 3D and 2D data from footage which
can then be used in many ways. The PixelFarm provides a number of
applets such as PFStable, PFRetime, PFPlate and PFBarrel to utilise
data from PFTrack to enable operations to be carried out in a host
compositing or editing application. In addition to match move tools,
PFTrack now includes full use of survey points, advanced Motion Capture
functionality, very comprehensive optical flow analysis tools and
colour keying for easy masking of green/blue screen shots.



PFMatch is a low cost fully-featured match move application featuring
the same industry leading tracking algorithms as PFTrack. Aimed at the
single desktop user PFMatch offers a low cost solution for markets such
as architecture or video users who require occasional match moving
facilities and do not require the rich feature set and cross facility
production tools of PFTrack. PFMatch hasmore tracking features than
many of the higher cost tracking applications. PFMatch stands out
against the competition due to it's ability to use manual, automatic,
or a combination of the tracking methods as well as solve all camera
motions including zooms.



Both products can be used to pass calibrated data from single or
multiple images and moving footage to PFBarn, a simple to use
image-modeling application for film pre-vis and set reconstruction.








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On-Set Tracking Tips














small
Tip Number 1 - Try Using Yellow Markers on Green



On green screen - use yellow markers and separate the components
separately for tracking and keying. On the left, you can see what the
full color rgb image looks like. Note that if you use the green channel
only (middle image), the markers are easily keyed and you avoid time
consuming marker removal. The red channel provides a great high
contrast image for tracking.





Tip Number 2 - Use Newspaper as Pattern for 3D Tracks



Newspaper makes an excellent tracking pattern for 3D trackers. If you
have a large green screen set, lay down newspaper away from the keying
area and the non repeating - highly detailed patterns of the news paper
will track really well.





Tip Number 3 - Marker Placement for 3D Tracks



If you are filming a greenscreen, it is important to not just have
markers on the same flat greenscreen background, markers need to be at
different distances from the camera for a good 3D solution.




small


Tip Number 4 - Round Adhesive Labels



Good premade tracking marks are as close as your nearest Office Depot
or other office supply store. Avery makes a variety of colored dot
stickers in a variety of sizes. Their web site shows a large variety of sizes and colors and don't take up much room in your travel bag.





Tip Number 5 - Keep the Greenscreen in Focus When it Makes Sense



For compositors, this is a pretty obvious tip. Sure, there are times
when this isn't a steadfast rule and the lens choice requires a
soft-focus background. But we mention it here because you might be
surprised how many times this isn't simply basic procedure on set. It
never hurts to mention it on a technical call, especially if you're not
going to be on set for the supervision. The first time you get back
some footage with all the tracking marks way out of focus and you don't
need it that way, you'll remember to mention this



Tip Number 6 - Special Case - TV and monitor screens



One area that people tend to "over mark" is when shooting TV and
monitor screens. Often the best comp can be done by shooting with the
unit just turned off instead of covering the tube with blue or green
screen. This let's you get realistic reflections that you can kiss back
in to make the comp better. You can usually pull tracks off of the
corners easily or off some detail in the case. If tracking marks are
put on the face of the screen, and you are trying to keep the
reflections, removing the marks can be tedious.



Obviously you will have to use some judgement on each shot. If someone
with frizzy hair is going to linger in front of the monitor you may
prefer to cover the face with blue or green material and add tracking
marks. This will result in you not getting any real reflections, but
general reflections can be faked easily.



One thing you DON'T want to do is let them feed a color generator to
the monitor - "look it's blue" ... this is a frequent production
thought and one that rarely works well, if at all.



Also check carefully thru the viewfinder for what is actually being
reflected to make sure it is what you want and is not the camera, some
lights and a crew member. Reflections can be hard to see on video
assist.





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