You aren’t wrong.
at a base level the animation speed can be calculated by placing the animation in blender or a 3d program and letting it play out with root motion making sure your feet do not slide.
This will always be an approximation since people have a different step cadence and no walk cycle is perfect when getting mocap data.
The thing is, in unreal, given the scale of things, an average 3rd person character moves very slow with a realistically timed walk/run. So for the most past people use values that play well and create manual animations to match those speed/feel natural at those speeds.
Anyway, goes without saying that the base animations are trash. There are a few packs out there with good locomotion if you want the cookie cutter solution. If you want to make your own i would suggest mocap if you can afford it, and making them manually if you cannot.
Its a job and with 0 knoweledge it takes a while, but its possible. The result will be better than the default animations if you put time and effort into it. You can also take the default and modify it to be on a specific scale.
To do this you use the same principle. A walk cycle is 24 frames. The speed in unreal needs to be solved to m/s.
Default export being 30fps you can set the root motion on the animation at 30 frames and just discard frames 25 to 30 later. The motion speed will be fine without additional calculations.
once thats set up you just need to adjust the position of feet/hip so that there is no sliding around when the animation is played.
This makes it so that there will be no sliding in unreal when the animation is played at full speed and the character moves at the pre-set speed. Should either condition change the feet will slide again.
To solve that there’s a few ways, the best one is a node that’s been around a lot. You can get it on the marketplace and update it to whatever engine version you are using.
the technique is called speed warping. You can check it out in many of the videos released about Paragon.
By now there’s 3000 implementations of it.
Note that nearly no AAA game gives a ■■■■ about any of this… Paragon was a good exception and great learning resource for how to do things more properly than most.
Hope the wall of text isn’t too much