Original subtitles

- [Instructor] A very common issue

when animating with a 3D character rig

is what we call knee pop and elbow pop.

I won't try to explain why this happened

but whenever you are extending the arm or the leg

using inverse kinematic, it can happen

that the knee accelerate to one full extension.

It creates a visual glitch that we will need to fix.

The first thing to do is to select the knee tweaker

and calculate its motion path.

As usual, I'm using my quick favorite, pressing the Q key.

Once that we see the trajectory of the knee over time,

it's pretty obvious where this pop or this break happens.

My technique to fix this is simply to reposition the knee

using the knee tweaker along the few frames

where it's currently popping.

What I advise you is not trying to fix this issue

on one frame only,

but instead try to smooth the motion path of the knee

over several frames.

Because if you try to fix it over one frame only,

you may push the controller into a weird pose

and you will generate a new problem

while trying to fix an existing one.

As you may have understood already,

the method is simply to rebuild the position of the knee

using the knee tweaker controller.

I first do it from the camera view,

but then don't forget to turn around your character

and check that the motion path look clean from every angle.

We do favourise camera view, but for this exercise,

I'd like our animation to be clean from any angle.