[Music]
lca2022
tna my name is joel um welcome back to
day two of lca's sessions
we have florian with you with us here um
florian runs the education business unit
at city network and has worked
exclusively with open source software
since about 2002.
florian has been involved with openstack
and ceph that's actually how i think i
first met florian a few years ago at an
openstack summit for my sins
and is involved with the open edx
educational project since around mid
2015.
florian is going to be talking and
covering the basics of stereoscopic
imagery and projection so we're going to
discover how stereoscopic vision works
and how we can trick our brains into
perceiving depth from two flat
two-dimensional images
this is not florian's first time at lca
but this is his first without suffering
through jet lag
um you can also get the slides for
today's talk um which someone will pop
into the chat um they have in-depth
notes and some details that can go along
with the talk today no my head am i
florian
thank you so this is my introduction to
stereoscopic photography
and videography and i do want to start
this talk with an important note on
accessibility so some of this talk does
assume that you have functional vision
in both eyes uh you will of course be
able to see the images and the examples
in this talk if you need to wear
corrective lenses i certainly need to
wear them too but if you do happen to
have very bad vision or blindness in one
eye then by the very nature of this
topic there's some things that you won't
be able to follow some examples that you
won't be able to follow and i do
apologize for that uh there's also a
specific condition called
stereoblindness which means that even
though both your eyes are completely
functional you're unable to perceive
depth so if you have that condition then
this talk might still be informative
stereoblind people have seen this talk
and then subsequently told me that they
took away quite a bit from it it just
might not be as immersive as it might be
for people with stereo vision and
likewise if you happen to have nystagmus
or strabismus some of those limitations
might also apply and possibly also if
you're using an artificial lens implant
which is common after cataract surgery
again i do apologize for that uh in this
case by the very nature of my topic
there's unfortunately very little i can
do to alleviate that however even if you
yourself cannot see stereoscopic images
and videos this talk does contain
suggestions on how to make them which
you can totally do even if you're making
them for somebody else
so with that said let's first get
started with
what stereoscopic vision or stereopsis
as it's called really is
and how it works so first of all what we
need in order to visually perceive depth
is two eyes and more specifically to
forward-facing eyes so this is something
that we humans have in common with say
cats or foxes or owls
that our eyes sit sort of on one side of
the skull facing what we call forwards
and they provide fields of view that
overlap to a great extent and that of
course comes at a cost namely the fact
that our field of vision is relatively
narrow so if you compare that for
example to the field of vision of a
horse where the eyes sit on the side of
the skull the animal has almost 360
degree vision only has a small blind
spot directly to the rear of the skull
and that's of course because a horse's
evolutionary survival technique is
flight so it's an herbivore and
basically the sooner it can see a
predator it can take flight and then it
can live another day
so it's kind of optimized for that
we humans are predators ourselves and
omnivores and we have evolved to sense
depth and that of course greatly helps
us in hunting particularly because we've
also evolved brains that enabled us to
make tools so if we make something like
a spear or a lasso or a kylie or bow and
arrow and we have an animal to throw or
shoot it at then it greatly helps us to
be able to sense intuitively but still
pretty exactly how far that animal is
away from us
so how exactly does that work and what
in our eyes and brains actually makes a
sense depth
and the first faculty that we need in
order to perceive depth is the faculty
of virgins so virgins is the ability to
align the axes of our eyeballs so a line
of sight as we call it um
align them and essentially make them
intersect pretty much arbitrarily in any
point in space in front of us
we might also be able to not make them
intersect like when we stare aimlessly
ahead but we can't really diverge our
eyes but we can converge them almost
arbitrarily and you can try that out
most people will be able to stretch
their arm out and then look at their
fingertip and then bring the finger all
the way in to the tip of the nose and
still look at the fingertip while you're
doing that and that might be very
uncomfortable because it makes you very
cross-eyed and you're not going to be
able to hold that for very long but most
people will be able to do that so we can
converge our eyes
almost arbitrarily
to a very extreme degree
and the second thing that we need is
accommodation
virgins gives us the ability to point
both our eyes at one point in space and
the other thing that we need for depth
of vision is accommodation which is the
ability to either stretch or to relax
the elastic lens in our eyes or the
thing that sits right behind our pupil
and do that in such a way that there's a
specific point in space or a specific
plane in front of us that produces a
sharp image on our retina in the back of
the eye
and commonly
the point where we verge and the plane
where we accommodate those intersect so
we're kind of looking at the same
spot in space in front of us using both
of those things but we don't have to do
that and we'll get to that in a second
but what that means is when we are
looking at something our eyes
fundamentally produce two images and
these two images are pretty much exactly
identical in one spot so the thing that
the spot that we verge on
and then they are slightly different
anywhere outside that spot
and this is what we call binocular
disparity and through what has to be an
inordinate amount of
trial and error and face plant
in our infancy what our brain learns is
to interpret these disparities between
the two optical inputs as cues about
depth
and it's by these differences that our
brain essentially builds a depth map of
our surroundings
so
now that we know how real depth
perception works meaning how our eyes
signal to our brains that an object is
at a greater or a lesser distance from
us we can talk about how we can trick
our brain
into seeing depth when objectively there
is none
so taking two
two-dimensional images and then making
our brains conjure up a
three-dimensional image from that
so for example
i've got two two-dimensional images here
um and this one might correspond to what
your left eye sees and this one
corresponds to what your right eye sees
so here's an example of such an image
don't worry for now about how we make
those and how we make that happen we'll
get to that in a jiffy but
the next thing that we need to talk
about is stereoscopic projection and
stereoscopic projection is about making
your left eye see only the left eye
image and making the right eye see only
the right eye image so that your brain
then puts everything together for an
illusion of depth
and there's multiple ways of doing that
so i'll start with something very low
tech a stereoscopic viewer or simply a
stereoscope i happen to have one here
let me swiftly explain how this works
there is a
little slider here and then you take a
print of a stereoscopic image that you
put in here you close the device so that
the print is jammed in place and can't
move about you bring the whole thing up
to your face and then you can look
through the eyepieces
and there's something important that
you'll see if you look at this little
device from this angle which is there's
a little black separator
let's see here right there's a little
black separator and it ensures that my
left eye can't peek over at the right
eye image and my right eye can't catch a
glimpse of the left eye image this by
the way is called a brewster type
lenticular stereoscope
and this was popularized by a chap named
david brewster in 1849 so it's about 180
years old
um
so that's a very low-tech device here a
slightly more high-tech is a
stereoscopic projector now stereoscopic
projectors came along for slides in the
1950s 60s
so the principle is this you've got uh
you've got a magazine of left eye images
you've got a magazine of right eye
images you put them into this projector
and they get projected out uh via two
different lamps two different projectors
and they are polarized the light damage
is polarized oppositely and then you
wear goggles so that the
stuff that is for your right eye that's
polarized one way is hidden from your
left eye and the thing that's polarized
the other way
that's for your right eye is hidden from
your left eye
and there are of course digital versions
of this as well they're available to
this day
there's also 3d tv which is a similar uh
concept except that you're not using two
projectors but you're using a tv screen
you've got one row of pixels
that um or one line of pixels that
emits light polarized one way and then
the next line the next row
emits light polarized the other way and
then you wear goggles and then that
picks everything apart again but that
too has a downside just as with the
polarized light projectors it's pretty
involved on the technology and logistics
side right you might need projectors you
might need a silver screen because you
can't
project polarized light onto a white
wall that doesn't work it messes up the
polarization on reflection you might
need a big screen tv your audience needs
goggles etc it's all very much
non-trivial
but what if instead we could employ a
technique that requires none of that no
special projection equipment no goggles
no nothing where you can literally hang
your stereo photography in a gallery and
visitors could just scroll through and
look at your images and see them in full
depth and such a technique does exist
and we're going to focus on it for the
rest of the talk and it's called free
viewing and it comes in two flavors
now freebie in general means that we can
take two stereoscopic images and we look
at them using a certain technique that
requires no stereoscope no projector
nothing all that you do need is two
functioning eyes and like i said they're
two flavors of free viewing and there's
one that's easy to explain and
understand but somewhat difficult to do
and there's another one that's a bit
more complex to explain and comprehend
but easier to do at least for most
people and i'll start with the one
that's easier to explain and then we'll
move on to the one that's easier to do
so the first one is called wall eyed
free viewing warlike stereoscopic free
viewing or sometimes called parallel
view so what i have here is a print of a
stereogram so it's the same image as the
one that i showed you earlier that
jammed into my stereoscope it's just
blown up a bit right again the left eye
images on the left the right the left
images on the left the right are images
on the right
so
if you were if i were to hold this up in
front of you and you were just looking
at this thing then normally what you
would do
is this your versions and accommodation
points would sit right on the surface of
the print so in this graphic here the
dashed line is the surface so that would
be the surface of the
of the photo that we're looking at the
dots are eyes the converging lines are
the lines of sight that meet at my
virgins point and the arrow represents
my accommodation so that is the plane
whose distance i set my eyes to
so
if i were to uh look at this thing or if
you were to look at this thing it would
look like this that's what your eyes do
naturally
but they don't have to
because what you can also do
is you can
instead of looking at the surface of the
print
you can look at an imaginary spot behind
the print
or whatever surface it is that we're
looking at just an imaginary spot behind
that surface while maintaining your
accommodation
as it was before
and if you do it just right then what's
going to end up happening is your left
eye looks just at the left eye image and
your right eye looks just at the right
eye image and then what you see is one
image that overlaps that's made from
both the source images and that
magically has depth
and i have an example up for you next so
you can try this out
so
i don't know if you're watching this on
a full-size monitor or a laptop screen
or a big-screen tv or your phone so you
may have to play with the distance
between your screen and your eyes a
little bit but the principle is in
general the same what you want to do is
you want to look over the top edge of
the screen at a spot in the distance say
a spot on the wall picture on the wall
or something like that
and that what you want to do is you want
to try coming down just a little bit
with your eyes so that you look at the
actual image
and not change the spot that you're
looking at in the process
and then what's going to happen is that
the left eye image is going to be right
in the line of sight of your left eye
and your right eye image is going to be
right in the line of sight of your right
eye and what's then going to happen is
that rather than seeing these two images
you'll actually end up seeing three
a left one that's blurry a right one
that's blurry and then a center one
from the other two overlapping that's
sharp
and that magically has
depth
so if you're not watching this live if
you're watching this on the recording
then now might be a good time to pause
the playback and perhaps give this a few
tries
for now i leave it up for a few more
seconds
you can simply try that out again
spot on the wall behind the picture
bring your eyes down so you look at the
picture and try
not to look anywhere but
distance wise but where you were staring
at
before
but
if this doesn't work for you
please do not fret
like i said this is the more difficult
method
and this is the one that actually
is
works for fewer people let's put it that
way
and i'll get to the one that's easier
for most people including myself
actually next
all right so if any of you have managed
to do this congratulations
we'll move on now
because the next um
option that you have is cross-eyed
stereoscopic free viewing or cross view
so here's how that works
what you do
is and you're probably already guessing
that right in a wall-eyed image so
parallel view our virgin's point is
behind the print
while we're maintaining our
accommodation on the plane of the print
or the plane of the surface
in a cross-eyed image it's in front of
the print so graphically it looks like
this
and what that means of course is that
now
your
right eye looks at the image on the left
your left eye looks at the image on the
right so
a cross view stereoscopic image is
actually reversed so camera takes these
pictures and then you reverse them
and the interesting bit about this is
that this is easier for most people to
voluntarily do i don't really know why
but it's certainly true for myself as
well so what you want to do if you
haven't done this before on the next
image is you want to cross your eyes
really hard
means you're totally overdoing it but
that's totally okay
and then you want to let your eyes
settle back to normal
and chances are that what's going to
happen is by the time your eyes cross
just to the point where everything falls
into place you get such a strong
stimulus in your brain that your brain
really doesn't want to let go and then
you see the depth image
so here like i said for most people the
next image will actually be easier than
the one that i just showed you it's
exactly the same motif it's just
the sides are reversed right and again
if you're watching this on a recording
feel free to pause the stream here pause
the playback and try this a few times
until you get the hang of it most people
will be able to do this
and by the way when you initially try
this it might actually help that you're
using an image that's relatively large
so it covers a rather large fraction of
your field of vision once you get the
hang of it doesn't matter once you get
the hang of it you can do cross view on
an image that's this tiny no problem but
for learning it it's probably a good
idea to start with a big image so again
what you want to do is you want to stare
at this image cross your eyes and then
let your eyes come back to normal
and at some point if you're lucky
things are going to click into place
again most people can't do this on the
first try
but if you give it a little time
and i'll actually shut up for a few
seconds now
so that you can try this out most people
will eventually succeed at this
and just in case i'm making the av team
nervous yes i'm still here it's all good
and if you actually manage to get the
depth effect what's going to happen
relatively quickly is you're going to be
able to see
the relative depth of
say these trim boxwood bushes uh you're
going to see what the distance is to the
various people in the image you're going
to be able to see the depth of the
stairs you're going to be able to see
the depth of the columns
you're also going to be able to see how
far the ridge line or actually the two
ridge lines are that are behind the
building
and uh
if any of you manage this now i'm
unfortunately i'm unable to look into
the chat right now but i'm really really
hoping that some of you um succeeded
this because when it works it's
uh it's it's uh it's it's a really sort
of satisfying feeling
so of course i'm not going to assume
that you're watching this through a 3d
projector and i also cannot assume that
you have a stereoscope at hand so from
now on for the rest of this talk i'm
going to default to free viewing and i'm
going to default to cross site
previewing specifically
so now that we've seen
what stereograms are and we've hopefully
learned how we look at them let's talk
about how we make them
and as you can imagine there are
multiple ways of doing that so
the first thing that i guess a lot of
you might think of is well maybe i need
to put a special lens on my camera and
such a thing totally exists so there are
stereoscopic lenses so for example um
the next one that i'm showing here this
happens to be a discontinued product but
this is a stereoscopic lens that you can
just put on a camera so you use it like
any other prime lens so you can do
autofocus auto exposure and whatnot and
it will create two stereoscopic images
in one frame
but if you look at this you will also
quickly realize this has a flaw
which is that the two lenses
are extremely close together they're
much closer together than human eyes so
that means this will make the pictures
heavily hypostereoscopic
so hypostereoscopic is
when the stereoscopic distance that is
to say the distance between the two
lenses or the two spots in space where
we took the images is a lot less than
the image between your pupils so the
distance between your i'm sorry the
distance between your pupils the
distance between your pupils is
approximately 70 millimeters and in this
case the lens has a stereoscopic
distance of maybe 10 millimeters and
what that means is that the stereoscopic
effect that you're getting from these is
a lot less pronounced you you'll get a
lot less
depth than you'd perhaps expect this
sort of lens is still interesting for
doing uh macro stereo photography so you
combine this with a macro ring for
example and that can produce really
really interesting results so for
example i've taken macro stereo shots of
tiny shells and that's very interesting
but sort of for general purpose use
this doesn't really work too well
but there's uh the next step which is
this thing here i actually have a prop
of this because i happen to own this
thing so it looks like this when it's
when it's attached to a camera right um
and this thing as you can see now that
has if i hold it up to my face that has
roughly the same distance as my eyes
and um this is something that we call
iso stereoscopic or roughly
isosteroscopic
so this thing here has a roughly 90
millimeter distance stereoscopic
distance um and that compares relatively
well to the typical 70 millimeters that
you have from from your eyes so
pictures that you take with this sort of
uh lens
the depth effect will roughly match your
natural stereo distance
and then there's one other thing that
you can use and uh those are
mirror lens attachments
so for example this thing this is called
the cooler deeper
and this is something it works through
an arrangement of several mirrors
they're all at 45 degree angles to the
plane of the sensor so the light path is
effectively deflected twice it's kind of
like this this shape and um
it offsets the light hitting uh the left
half of your sense a little further to
the left and offsets the light hitting
the right half of your sensor a little
further to the right and so that makes
this device slightly hyper stereoscopic
so if we have a stereoscopic distance
that's larger than
the distance between our pupils we call
that hyper stereoscopic so in this case
it's about 105 millimeters this by the
way is really a design that's made for
sort of full-frame
dslrs uh it also has like another
small version that you can clip onto
your phone but this thing is very much
made for sort of big dslrs
but just like i can scarcely expect you
to have a stereoscope in your possession
or a stereoscopic polarized light
projector i can scarcely expect you to
have these devices in your possession if
you want to get started with 3d
stereoscopic
photography and so because i of course
want to get you interested in it i'm
going to start talking about gadget free
stereograms so stereograms that you can
create with any regular camera
so i'm about to show you a stereo
photography technique that works with
literally any digital camera at all so
you can use your dslr you can use a
point shoot camera you can use a gopro
you can use your phone anything
now
i'll have to mention that this is a
technique that doesn't work for candid
shots and it doesn't work for action
shots but you can make absolutely
stunning 3d views of buildings and parks
and statues and sculptures and
landscapes and you can even do post
portraits this way so if you have
somebody that can actually sit for a
portrait for you and can hold still for
like 15 to 30 seconds then you can
totally apply this technique to
portraits as well
and i have a small video uh for this
that i'm going to narrate over
so this is me
in my backyard
taking an image of this little garden
ornament that you see and the technique
is really simple i lean on my left foot
so i've got all my weight on my left leg
i snap a picture and then i move over i
move my weight over to my right leg and
snap another picture
that's literally it right
i'm going to give you this on a loop so
you can see it a few times but it's like
really really simple what you want to do
weight on your left leg snap
shift your weight over to your right leg
snap and what that will create
is two images
that have a stereoscopic distance of
about my shoulder width right so they're
pretty solidly hyper stereoscopic even
and if you want to uh take a look at how
that works or how that looks from the
camera this is a view
of the android open camera app exactly
the same thing right so i
frame
the shot with this little ornament in
the center click and then i shift my
weight over
and the whole shot changes a great deal
but the this garden ornament stays in
the center click again
and that's it right
so that's how i create my source images
very simple way to create stereoscopic
images and now how do i turn those into
a stereogram
so we've got two images and now we want
to make a stereogram out of that right
they're not aligned they're not like
whatever and we can do that in a few
very simple steps and of course as
everything as with everything else that
i'm showcasing in this talk i'm using
exclusively free and open source
software
so we're going to do this with the [ __ ]
the canoe image manipulation program
so
what do i do here
well i i've got my two images and i open
them using the open as layers function
in the [ __ ] right so that will simply
create two layers created from these two
images
and now what i'm going to do is i'm
going to rename my layers and i'm going
to rename them left and right
so that they reflect sort of
you know what the view is and then what
i'm going to do is i'm going to take my
right
layer the one that's currently in the
foreground and i'm going to reduce its
opacity to 50
right so that's semi-transparent
and now what i do is i use the [ __ ] move
tool
and
what i want to do is i've got this
little garden ornament that i've
centered as sort of my focal point and
my center of attention and what i want
to do is i want
the image to precisely overlap on that
little ornament so i zoom in a little
bit and i wiggle stuff around until it's
just right
such that i get full overlap on that
little ornament
right just there every everywhere else i
don't care
and then what i do is i do a simple
rectangle select
because now my my layers are only
partially overlapping right and what i
want to do is i want to select the
portion where
they overlap right and i do that with a
simple freehand rectangle select i'm
sure you can write a plugin or a script
or something for that as well but i do a
simple
freehand rectangle select
and once i have that i can use the image
crop to selection option crop to
selection cuts through all the layers
and that means i now have layers that
are exactly identically sized and then
have this little garden ornament in
the center or
that point is is precisely overlapping
and now i have to decide do i want to
make a cross-eyed or a warlike image and
i want to make a cross-side image so
what i do now is i take the right layer
and i move it to the left
right and that creates my cross view
image and then of course you know it's
invisible so i have to resize my canvas
to the layer sizes that's trivial and
then i do one other thing
i leave a little bit of a gap between
and then i create um
a single unique color layer i usually
use white or black and then i put that
into the background because what that
does is it creates this little bar in
the center and when viewing that kind of
tends to nicely frame the image and
guide the eyes right
so that's my stereo my stereogram that
i've created in just a few minutes of
the [ __ ] and this is the result
right so this is a cross-side stereogram
again i'll leave this up for a few
seconds admittedly this one is more
difficult to do than the others because
the background is a little busier
but if you've
managed to do a cross-eyed view of the
image that i gave you earlier chances
are that you're going to do fine with
this one as well
the only thing that you want to perhaps
keep in mind is you want to keep your
attention focused on this little orange
glass bit of of that garden ornament
so you can so you can focus on that
and again i'm going to leave this up for
a few more seconds
and then hopefully what you're going to
see is the depth differences between
this little ornament
and the lilies and the little
maple tree that's growing there and uh
and everything else and the fact that
it's sort of staggered in in depth and
and distance
and that's how we create stereograms in
just a few minutes in the [ __ ]
all right
on to something even more exciting
stereoscopic motion picture aka 3d
movies or motion stereograms so there's
one thing that i think is probably
self-evident right which is that
everything that i talked about for still
photography that relied on using special
lenses or lens attachment or something
like that all that also goes for for
videography right because your dslr or
any other camera including your phone
really can do video just as well as
still so if i if i use this
just you know my regular camera which
can of course do video and i attach this
lens to it then
i get 3d video from that right
but
i'd argue that most people today will be
interested in using a different kind of
camera for
3d video namely a drone camera i don't
know about you i love aerial videography
i think it can be absolutely amazing to
begin with and now imagine shooting
aerial video that's stereoscopic right
now of course what you could do is you
could build your own drone perhaps
something like a fixed wing uav that has
a wingspan of two meters and it has a
gopro embedded in each wing and that
would result in sort of seriously hyper
stereoscopic image and it will give you
the impression or the feel of being
something like a pteranodon science
creature soaring over the earth
but there's a few issues with that right
one we're not all triggered
two
it would come at significant expense and
three you'd need an airstrip for this
whole thing to sort of take off from and
land on right so that's perhaps a bit
problematic
but
there's something very exciting that you
can do you can totally get 3d footage
with a single camera
one that's mounted it could be mounted
on your drum but it could also be
mounted on your car your bicycle
wherever so let me quickly explain the
principle so you already know that any
stereogram consists of a left eye and a
right eye image and of course that also
is true for a motion stereogram but i'm
talking about having only one camera
with only one lens right so imagine
let's take this this gopro here right
and i hold it up to my right eye
right so that's my right eye view
but if i have only one camera where's my
corresponding left eye view
well once i add some sideways motion
right
sideways motion relative to where my
lens is pointed then you quickly realize
that my left eye view is simply where my
right eye view was a moment ago
and we can harness that fact in video
post production to create a 3d video
from a 2d video just as long as it
includes constant lateral motion
so how do we do that
right how do we harness sideways motion
for a 3d effect there's a little bit of
very simple maths that we need to do for
that so suppose that we're shooting uh
video at 50 frames per second right
so that means that um
we're
every frame is 20 milliseconds in
duration
so therefore if we're moving
perpendicular to the direction of view
okay so the camera's pointed this way
we're moving that way
um and we're doing that at even one
meter per second which is roughly the
speed of a leisurely walk and of course
also means that we're moving in one
millimeter per millisecond right so that
means that one frame covers about 20
millimeters in sideways motion
so therefore if we duplicate our stream
and put the two stream copies side by
side and then offset one of them by four
frames
or 80 milliseconds
then what we've effectively achieved is
a stereoscopic distance of 80
millimeters
and
our pupils are 70 millimeters apart so
that's nicely
iso stereoscopic
if we go a step further and uh
we
uh
make with we're thinking about an object
that goes a little faster so say for
example a drone right or a bicycle or
something like that a car is easy
but any any of those can achieve 10
meters per second right
or 36 kilometers an hour um
so when you do that then even a single
frame offset gives you a stereoscopic
distance of 200 millimeters right which
already makes the video solidly hyper
stereoscopic and if you use for example
a five frame offset it gives you a nice
giant's eye view with like a one meter
stereo distance and this becomes
especially interesting when you're
either doing a linear drone flight along
a roughly linear feature so say for
example you're tracking a coastline
or you're doing orbital flight around an
object right so ideally one with where
you're orbiting above
and your camera is is tilted slightly
downward
and i've got an example of the former of
these two so what you see here
is a drone flight sequence that's shot
at 30 frames per second with the camera
pointing forwards and the drone flying
sideways
um and it's going to the right and it's
going at approximately 40 kilometers an
hour or 11.1 meters per second right or
put differently uh this is buffering a
little bit but
you can
follow the um you can follow the video
stream in the in the slide link that we
uh shared at the top of the talk so
anyhow um
the we're going uh sideways at 11.1
meters per second
camera is pointing forwards put
differently drones flying forwards at
11.1 meters per second camera is
pointing 90 degrees to the left it's
exactly the same thing so and i it bears
mentioning that um the camera doesn't
need to be pointed at a 90 degree angle
versus the heading of flight uh we could
also for example be pointing the camera
directly short and then fly at the beach
at a 45 degree angle but what matters is
that we have some lateral motion and
that we're able to quantify it which
which saves us some guesswork
so every time every 90 milliseconds
the camera is laterally displaced one
meter and that's a nice hyper
stereoscopic distance that we can work
with in this panoramic shot so how do we
turn this into
a 3d movie
again
wonderful open source software to the
rescue this is my favorite video editor
happens to be shortcut
and what you see here is i've got the
same video opened twice in shortcut in
my playlist that's just a ux quirk in
shortcut um
i need to do it this way because there's
certain things that i can't do with one
of them never mind it's exactly the same
the same sequence so what i'm doing is
i'm adding a video track
for the left eye image
and note we're again going to be making
a cross view video so this image will
actually end up on the right so i'm
pulling this clip down into into the
track here
and then what i'll do is i'll apply two
filters very simple filters so the first
one is a crop filter
and what i want to do is i want to sort
of extract out of this
widescreen view i want to extract sort
of just the middle bit
and so therefore
what i'm going to do is i'm going to
take a crop
of half the width of the whole frame
so it has an original width of 2704 so
i'm going to drop it to our 1352
in width so 1352 pixels and of course
the height stays unchanged
and then what i'll also do is i'll
offset my crop
[Music]
by one quarter of the image width so
that's 776 pixels that you see here so
what we're chopping out we're taking out
sort of the left and the right side and
we're just leaving the middle
okay and now what i'm going to do is i'm
going to use a position filter to move
this cropped
frame
all the way over to the
right all right it's the left eye image
it moves over to the right because we're
building a cross view video
all right so
that's
the left eye image
now add a second track pull the exact
same video into that track
and then we're also going to be doing a
little bit of play with filters
so there we go we're pulling that down
uh into our track at this point it's
it's identically aligned and now uh
we're applying the same filters
so first a crop filter the crop filter
is going to use exactly the same
parameters as
with the
left eye image so we're going to
reduce its size its width to 1352
and we're going to
use the middle portion so we're going to
offset this by 776 but now i do
something i do the reverse of what i did
earlier with the position filter with
the position filter i now use a negative
776 pixel offset so that this thing
moves to the left gets jammed over to
the left
uh the left edge of the frame and then
there's one tiny little thing that i
need to do i have this bar here that
overlaps and of course i don't want that
so uh what i'll do is i'll change the
blend mode
to add and there we go so now we've got
the two images side by side
and now comes the magic right so now
what we do is we take one of our one of
our tracks
and we offset it
by 90 milliseconds versus the other
all right and so what i'll do here is
this takes me a little bit of fiddling
because at the time when i uh when i
screen capped this i didn't know the
shortcut yet to make this happen in
shortcut so forgive me for that so i'm
just positioning the playhead i'm
roughly eyeballing this to
.09 seconds
and then
once i found that which like i said took
me a few tries
i can
move and then split my tracks
so
so there we go now we're moving that one
track by that offset
and now everything else that remains is
just trimming
right we're trimming a little bit at the
at the start and we're trimming a little
bit at the back and then we're moving
everything back to
this to to the beginning of the track to
the start of the track to the zero mark
okay so there we go
i just find another spot here with the
playhead again i completely eyeball this
and i split
and i trim
and now that that's done i just move
everything to the start of the track
and that's it
and now we can render this thing
and we end up with
a 3d video
all right
so again this is exactly the same
principle you cross your eyes
you let them wander out a little bit and
you wait for them to click into place
right again if you're watching the
recording or maybe you're watching the
original on on youtube you probably want
to pause the stream at some point and
just find your find your spot at the
very beginning of that loop there's a
house in the middle that kind of lends
itself to being a nice little focal
point
and i'll give you this on a loop here a
few times as well
i realize it's probably a little bit
jerky right now like i said you've got
all the links available and you can look
at the original footage but in principle
this works exactly the same way as a
stereo photograph
and once you get the hang of it it's
really nice because in this case you
sort of see how
there's like different layers of depth
in the jungle that are staggered uh
there's houses kind of like in between
there
and and they are all at like different
depths there's two ridge lines in the
back actually three ridge lines in the
background and you kind of nicely see
the relative depth of those and and so
on and it's it's it's pretty neat uh
when it turns out that way and that's
how we get 3d footage of flying along a
brazilian beach with a view of the
jungle with just a single camera
now
uh with that
i hope i've peaked your curiosity for
stereoscopic photography
a little bit
and i'll have a few more stereo images
here to close out the talk for those of
you who have already mastered the art of
cross site previewing these will
probably be a breeze
so this here is a shot
of
reconstructed roman baths in what used
to be the capital of uh the roman
province of pannonia superior in
kanuntum uh today this is about a 45
minute drive away from
vienna 45 minute drive east of vienna
approximately
and that gives you uh when when that
clicks into place that also gives you
sort of a nice view of the relative
depth of the buildings there's these
neatly trimmed bushes in front uh
there's some trees in the background
uh and so on
uh here's
another image coming up now
that apparently takes a little bit to
load
for some reason and i'm not really sure
why
that's great florian i'm just imagining
this talk in real life uh at the
conference and a room full of lca is
stumbling around during the broom
changeover
trying to uncross eye themselves
um we do have one question from the chat
if you've got got a moment to take it
um have you tried using any of the
various vr headsets that are in the
market as a stereogram viewer
i have not
but in principle
and i have another version of this talk
in which i mentioned this so basically a
vr goggle
works very much the same way as a
stereoscope like this except that rather
than putting a photograph an image in
here um you've got two screens right so
in principle it's it's pretty much the
same thing no i have not used it like i
said like for me this is uh i mean yes i
use all these digital tools and whatnot
but for me viewing this uh is sort of a
low-tech hobby i want to i want to put
this stuff sort of on my wall and and be
able to to look at that um i know we're
almost out of time i do want to mention
uh just a couple of more things because
they're important um i my twitter handle
was already sort of all over this talk
um if you do engage in this sort of
thing please tag me i'd love to see your
stereo images and uh there's another
thing that i do want to say which is a
special thanks to my former colleague
adolfo branches who took the drone
footage
from the brazilian beach and gave me
permission to use it and i also have a
few
creative commons image credits to share
at the end of the talk do we have any
more questions
uh yep we have one more how does this
relate to magikai books from back in the
day
magic ibooks are called auto stereograms
so
that's um
yeah i mean
that's also it's it simply creates the
illusion of depth in a different way
namely by using these actually they're
probably called random dot stereograms
so anything that you can free view is
essentially an autostereogram pretty
much um and those are called random dot
stereograms so yes it's pretty much
similar
it just yeah it just doesn't come off
sort of the living object right but it's
but it's generated there's also people
that do things like taking
uh letting [ __ ] build depth maps from
two different
uh views
left eye and right eye views of an image
and then creating random dot stereograms
from that but that is something that i
just know exists i haven't dabbled in it
i don't know anything about this uh but
yeah it's it's something uh
well it was brilliant thank you very
much um
thank you actual feedback was really
good from the chat really good
engagement everyone was trying out the
the cross side and different methods it
was great okay thank you and now we'll
be back in 10 minutes after the room
changeover
so thank you once again florian and
we'll see you hopefully at the next lca
yes exactly stay safe and healthy
everybody and i hope to see you next
year cheers