Hi, i’m new to game developing, and i’m having some doubts about the skeleton of my model.
I’m not sure how “root bone” does work.
Must i add a bone to the floor, and then, set that bone as parent of the hips? (hips is the parent bone of the hierarchy/bone tree)
(sorry for my english)
With a root bone you can move the entire rigg -> ?v=ysMueIma_-E
Well a root bone is just that. It is the first bone in the parent child hierarchy that will both translate or rotate the model relative to world space. The hip bone in most cases will be the root of the player model or whatever mesh/rig is connected to it.
Adding a bone, let say, relative to the floor is usually called the reference even though in fact it is a root of all the other bones connected to it but serves a different purpose as to a given application or need.
A good example is if a skeletal mesh is moved from one application to the other the two might have a different requirement as to the direction that the character must face relative to world space and if it does not match it’s an easy process to change the relative position of the reference as the root then it would be to change the orientation of the model if the hips was the root.
thanks for the answers, it’s much more clear now 
One important detail is that having a Root bone above the hip allows the animator to separate hip movement from root motion. The character can run with side-to-side hip movement without actually affecting the root motion itself. Being able to control root motion separately is a powerful tool.
Just in case when you want to use root motion: https://docs.unrealengine/latest/INT/Engine/Animation/RootMotion/index.html 
Yeah root motion is awesomeness. Having a player model in an FPS go outside the box with out collision is a bad thing.
I do have a question myself I’ve yet to try.
Can a player model support more than one capsule?
Or
Can a capsule be added to skeletal rig
and both will respect collision?
The context is our game has guns and having them clip walls is not a good thing.