What's root motion?

Hello, lately i bought the movement animset pro
i found that there are 2 types of animations: normal ones and root motion
can someone pls explain me what is root motion?

Root motion allows your character to move as part of the animation, but still have collision. It is done with an extra root bone that itself never moves.

You can find an example on the content examples project, open the animations map and walk around till you find it, it has an example of an animation with and without root motion.

Here’s the docs on it, watch the animations to see how it would be used in something like a power move where a character takes several steps forward during the move:

ok thank you for the explanation.
for example, if i have a set of animations where the skeleton have a rootmotion and i want to target those anims to one of the mixamo characters (from the free pack, they don’t have the rootmotion bone)
will that work or not?

Root motion is calculated from the motion of the very highest bone in the skeletal hierarchy (the literal root, of which all other bones are children). The engine measures the delta of the location of that bone, removes it from the motion of the bone itself, and applies it to the actor which has the skeletal mesh instead.

Every skeleton, by definition, has a single root. So it SHOULD be retargetable, at least in theory, because there is no such thing as a skeleton without a root bone (and therefore incapable of root motion). The issue becomes whether or not UE4’s retargeting is intelligent enough to retarget from one root to the other, especially if the roots are in different places (usually root bones are at 0,0,0 but sometimes they’re placed at the hip instead) and can’t speak to that as I’ve never tried.

this is the documentation from unreal for retargetting mixamo free characters with any animations that use the unreal skeleton
as you’ll see the root isn’t retargeted to any bone

This is because sometimes a skeleton has two “root” bones (though only one ACTUAL root bone).

Naming conventions (especially for human skeletons rigged with IK) sometimes names the hip bone “root” and the actual root bone “master”; for example, MakeHuman rigs are this way.

I don’t know about the documentation but I absolutely assure you that the UE4 Blue Man has a “root bone” in the sense implied by Root Motion. In fact if you look at the picture on that page you’ll see the point at 0,0,0 that all bone positions (white lines) are drawn from; that is the Root that Root Motion is observing.

When is the best time to use the root motion animations as apposed to ‘In place’? I’ve read the documentation where the example is an attacking with hammer sequence but can normal looping anims like walk and run be the in place versions?