Hi, I’m sorry about the noob question, please forgive me I’m quiet new at UE4
I watch a lot of UE tutorials and read the UE’s explanation page but I still can’t differentiate what happen if we are using the root motion and not? please dumb it down for me to understand.
A lot of the video always using root motion, is there a scenario where we don’t need to use it?? (When we should use it and when we did not need to use it?)
Thank you
Animations can be authored including root motion or without root motion.
A walking animation without root motion will simply walk on the spot. This is called Game Driven motion where you decide how fast the character is moving and play the correct animation to match. This is what the ThirdPersonCharacter does when you create a basic blueprint example project. It has a walk and a run animation and uses a blendspace to decide which one to play depending on what speed your character is moving at.
The downside is that you can end up with a character moving but the amount of times the feet touch the ground don’t match the speed perfectly so the character can seem to float along.
A walking animation including root motion includes how far the character should be moving forwards for each frame of the animation. The root node contains the information about how far the character should translate - hence root motion.
This is called Animation Driven motion and the animation that you play determines how far you travel. It gives you motion that should perfectly match the distance covered and get rid of that floating effect if you implement it properly.
A useful overview summary of the two is in the following video (starts about 5 mins into video.)
Root motion means, that the root bone of an animated character is moving, while in non root motion, or in place animation, the root bone does not move. This is contained within the animation sequence.
With in place animations, the locomotion is done by moving the player capsule controlled by the player controller. The animation to be played is determined by the movement of the capsule. If it is moving forward, play a walk animation, if it is even faster moving forward, play a run animation. This for example can lead to sliding feet on ground effect, if animation sequence and character speed do not match.
With Root motion, the overall movement into a direction is already contained in the animation sequence itself. The player capsule itself does not need to be moved at all to make the character move forward. This allows to avoid sliding feet. But it has other side effects for collision - because the capsule, which is used for collision detection, is not moved. So the character mesh moves outside the capsule.
You should carefully read this doc, which really explains it perfectly, as well how to handle it.
Also, you might get a (free) account on mixamo - here you can play around and preview animations and they have some with / without root motion, where you can compare both.