Before we get to regain our own character, there's a concept I need to explain, and that's the difference
between inversed kinematics and Ford Kinematics or IRQ versus F K for short.
And I k we have already seen where if I select control and I move it around, all the other bones will
follow that movement.
OK, that's inverse kinematics, meaning it's figuring out the motion based on the inverse of where
the point is ending up.
Right.
So that's one way to think about that.
The other that we haven't seen yet is basically the origin of 3D animation.
This is how everything was animated, like the original Jurassic Park.
This was animated with Ford Kinematics.
Now, if I wanted to put his hand on his head, I can just click it and put it on his head and now his
hand is on his head.
If I wanted to do that with Ford Kinematics, well, I would have to do is select the bone rotated up
there, each bone individually, and I could eventually get it up there.
All right.
Same pose, but with two different types of rigs.
And you can quickly see the difference, right?
If I especially with the legs, if I move the center of gravity or the cog and I move it down.
His shorts aren't following, first off, but his feet are staying in the same place.
Right.
That's because those are in the world space.
They're not following the route of the body so he can stand on the ground.
If I do the same thing with Ford Kinematics, everything moves together, right?
Because it's all expecting to be adjusted from these joints.
So I could move him down, then I would need to move both of these up and then move both of these down.
And hopefully that would be somewhere on the ground ish.
And this is actually how the original Jurassic Park was animated.
They didn't have inversed kinematics back in the day.
So this is kind of the origin of 3D animation is with Ford Kinematics and still used a lot today.
Because let's think about it another way.
If I wanted to have a nice arc with the hand, let's say I want it to rotate this like this.
Right.
Has a nice arc.
If we're watching this joint, OK, it's following this arc because it's being rotated from this pivot
away from itself.
So there's a nice arc as he's throwing a ball or something like that.
If I want to do that with inverse kinematics, I can bring the hand out here and then I would have to
adjust the elbow to try to stay back here and then move this down.
And the quick rig is actually kind of a different type of inverse kinematics, I could actually use
the shoulder here.
So it's trying to do a hybrid approach, but typically with an inverse kinematics, you would have to
kind of position this thing and then reposition the elbow and constantly go between those two things
to try to get that rotation like bothering a hand.
So there's trade offs for each one.
Right.
And it's going to depend on what your character's going to be doing.
Same thing.
If you know that we saw with the feet not being on the ground, that's going to be the same thing with
the hands in our earlier example of if his hand was touching a table and he was rotating, you know,
this also wasn't following because it's in the relative space of his chest.
It's going to follow his chest.
His arms are following his chest.
Right.
Whereas his feet don't do that.
So that's the space that it's in is a different component of it, right?
It's a different component of emersed kinematics.
So even though these both look the same, if we're rotating the chest like this, they're not right.
And we can see why very quickly when we just select the rest and move it.
We can't really do that.
If we select the rest to move it here, it's not going to like that.
So that's the difference between inversed and forward kinematics and how it's going to affect your posing
and animation later on down the line.
What what we will do is we will do an Ike setup and there are some rigs where you can actually switch
between.
I can.
And they use very somewhat complicated math to figure out the vectors so that you can switch and it
matches the pose, but we're not going to get that far into it.
That's an advanced topic that maybe I'll discuss in another course.
So to keep it simple, I just wanted to show you what Ford Kinematic says, because, you know, this
is for the history of animation and for your your full understanding of what rigging is and animation.
You need to understand both concepts.
But for our rig, we're going to focus on Ike mostly, and that's how we're going to build our rig.
In the next lesson, we're going to start to rig the Bones character that we modeled and textured in
the previous parts of this course.
Thanks for watching.