Dear Fellow Scholars, this is Two Minute Papers with Dr. Károly Zsolnai-Fehér.
Today we will see how this AI-based technique can help our virtual characters not only learn
new movements, but they can even perform them with style.
Now, here you see a piece of reference motion - this is what we would like our virtual character
to learn.
The task is to then, enter a physics simulation where try to find the correct joint angles
and movements to perform that.
Of course, this is already a challenge because even a small difference in joint positions
can make a great deal of difference in the output.
Then, the second, more difficult task is to do this with style.
No two people perform cartwheels exactly the same way, so would it be possible to have
our virtual characters imbued with style, so that they, much like people, would have
their own kinds of movement?
Is that possible somehow?
Well, let’s have a look at the simulated characters.
Nice, so this chap surely learned to at the very least reproduce the reference motion,
but let’s stop the footage here and there and look for differences.
Oh yes, this is indeed different.
This virtual character indeed has its own style, but at the same time, it is still faithful
to the original reference motion.
This is a magnificent solution to a very difficult task.
And the authors made it look deceptively easy, but you will see in a moment that this is
really challenging.
So how does all this magic happen?
How do we imbue these virtual characters with style?
Well, let’s define style as a creative deviation from the reference motion, so it can be different,
but not too different, or else, this happens.
So, what are we seeing here?
Here, with green, you see the algorithm’s estimation of the center of mass for this
character.
And our goal would be to reproduce that as faithfully as possible.
That would be the copying machine solution.
But, here comes the key for style.
And that key is using spacetime bounds.
This means that the center of mass of the character can deviate from the original, but
only as long as it remains strictly within these boundaries.
And that is where the style emerges!
If we wish to add a little style to the equation, we can set relatively loose spacetime bounds
around it, leaving room for the AI to explore.
If we wish to strictly reproduce the reference motion, we can set the bounds to be really
tight, instead.
This is a great technique to learn running, jumping, rolling behaviors, it can even perform
a stylish cartwheel and backflips.
Oh yeah.
Loving it.
These spacetime bounds also help us retarget the motion to different virtual body types.
And furthermore, it also helps us salvage really bad quality reference motions and make
something useful out of them.
So, are we done here?
Is that all?
No, not in the slightest!
Now, hold on to your papers because here comes the best part.
With these novel spacetime bounds, we can specify additional stylistic choices to the
character moves.
For instance, we can encourage the character to use more energy for a more intense dancing
sequence, or, we can make it sleepier by asking it to decrease its energy use.
And I wonder if we can put bounds on the energy use, can we do more, for instance, do the
same with, for instance, body volume use.
Oh yeah!
This really opens up new kinds of motions that I haven’t seen virtual characters perform
yet.
For instance, this chap was encouraged to use its entire body volume for a walk, and
thus, looks like someone who is clearly looking for trouble.
And this poor thing just finished their paper for a conference deadline and is barely alive.
We can even mix multiple motions together.
For instance, what could be a combination of a regular running sequence, and a bent
walk?
Well, this.
And if we have a standard running sequence, and a happy walk, we can fuse them into a
happy running sequence.
How cool is that?
So, with this technique, we can finally not only teach virtual characters to perform nearly
any kind of reference motion, but we can even ask them to do these with style.
What an incredible idea.
Loving it!
Now, before we go.
I would like to show you a short message that we got that melted my heart.
This I got from Nathan, who has been inspired by these incredible works and he decided to
turn his life around, and go back to study more.
I love my job, and reading messages like this is one of the absolute best parts of it.
Congratulations Nathan, thank you so much, and good luck!
If you feel that you have a similar story with this video series, make sure to let us
know in
the comments!
Thanks for watching and for your generous support, and I'll see you next time!