We've got a robot arm down the hall that we use to do plant deconstruction.
Uh, maybe that's for another video.
Offscreen Speaker: Well sh..should we go and see what it ..
can we... look at it .. or?
well? we ..we might be able to look at it!
It'll be messy because um
you know. Its a Phd student.
Of course the doors might be locked. He might have gone to the gym....
(He) spends a lot of time in the gym.
(sound of doorknob turning)
(subltle door creak)
Here we go!
So its.. its in some sense in the prototype stage
So you know, lots of cable around...
But you can see its basically...
taking pictures of ... the ... plant.
And actually in fact the.. the camera here is static.
and at the moment, the turntable is moving.
And this is our tame phd student, Jonathan
The way that this works
is that the camera will try and move to get the best possible view
of..
*aside* I actually move outta the way of this Offscreen Narrator: (friendly chuckling)
Offscreen Narrator: Right lets just see what that says
"Do not touch any of the equipment"
Yeah, I come here and move it about when hes not here just to annoy him
uuuhhmmm
So! ...but..
what it will do is try to move to get the best view of the plant it can
some plants are different sizes, so you're gonna have to move backwards to get them into shot
some of them are smaller with more intricate leaves, and you're gonna try and move in closer
so this is still a work in progress
but its something we're working towards
space carving is one of the things we're examining here
but we're obviously doing a lot of other stereo matching, and some RGB stereo as well.
we talked about stereo matching, right?
so we've got some cameras andd we've calibrated them. We know where they are in 3 dimensions.
and then we can use, uh, feature correspondence between different images
to work out how far away something is
or lots of things in the scene
and we can begin to build up a disparity map
now..
there are lots of ways of doing this
today we're gonna talk about one that's slightly unusual
that does see quite a lot of use in research in academia
uhm. and.
...in...
client science and things like that where I obviously do a bit of work.
I mean that's called "space carving"
"Space carving" is the idea of, in a sense, of starting with a big lump of clay
Working out where you know your object is not
and cutting that clay away
until you get something that kind of resembles what you know your object is supposed to be
except, its based only on what you can see in 2-dimensional images
so a good example would be if I give you this, if I show you this..
alright what... what's that?
Offscreen: er. ok?
Thats a serious. its not... its not a trick question
offscreen Narrator: Okay well that's obviously...a..a mug. Its a cylinder with some ..uh
(Interrupting) It is a mug, right !?! ...Its a cylinder with a handle on it
which is... ...I don't know what the shape of that is
Right?
But the thing is you can't absol-
you can't acutally be sure.
ok you've only got one camera. You're looking at it from this direction.
This mug could go off for one meter.. backwards!
into this wall.
and you wouldn't absolutely be sure that it didn't do that
apart from your intuition about what it is.
ok?
and, and the fact that you're a human. You know its a mug.
Offscreen narrator: I mean, thats..(stammering) .. sorry
its just that because i'm on the handheld and not on the tripod I can move side to side...
(interrupting) You can move side to side, ok?
So one of the ways we work out what an object shape is
truly, we move around it and see it from other angles
ok? or we rotate the object and find out it isn't in fact a meter long
because I would have just hit myself in the head! (offscreen laughter)
Ok? ...so!
but the point is that until we see it from a different angle we can't be absolutely sure
now in .. on a computer...
that's more true, even
because they can't intuit anything
they..
so ...
they say: "well? its a square box with a 'lil circle on the end of it"
and that's all they can tell us!
ok? they can't tell us what shape it is,
they can't tell us that its hollow
uh. or anything else
because uh.. how?... how would they know?
how would they know that it isn't longer this way?
ok?
unless we start to build in some sort of rules.
so, what space carving does
is
look at this mug
and
try and carve a piece of clay in that shape
ok?
but under the assumption that it could go back here
right?
then we turn it and go: "oh! it doesn't."
and cut that bit off
and then we turn it again. And we cut that bit off.
and we keep doing this until we cut off as much as we can
the more views we get the better that..that the..
...the result.