V0.0.1 Devlog - LH

Complications With Motion Matching

Author: Liam Hans

Posted on: 06/14/24

THE PROBLEM

As the primary player programmer for our first week of development, my job was to import our desired player avatar into our engine and get him animating. At first, I thought this was going to be a relatively simple task, and in some ways it was, but in other ways it was a bit of a headache. Because we are using Unreal Engine 5.4.2, we decided to take advantage of the Motion Matching feature that they offer. Motion Matching, in simple terms, takes your character's current trajectory (direction and input level/speed) and chooses the most appropriate animation to play for said current trajectory. For example, if I am moving my character to the left at half input on my remote controls stick, it will choose a slow strafe animation, as that animation's trajectory matches my characters trajectory. It's a bit more complicated than that, but that's essentially the gist of it. 

With this new system, your character and their animations are required to have root motion enabled, meaning they both need to have a root bone. Unfortunately, characters and animations from Mixamo, one of the only sites to get an abundance of free characters and animations online, do not have a root bone, meaning motion matching does not work as intended with assets exported directly from their site. To be more specific, when I enabled root motion for my animations, they would flip 180 degrees and be upside down for some very strange reason. This was obviously a big problem for me, but luckily there was a convenient solution.

THE SOLUTION

There is some rather handy software online called "Mixamo Converter" that does a number of things with Mixamo assets; one of those things being the ability to convert your animations/characters from root boneless to root boned. Upon finding this software, I was able to add a root bone to my character and his animations. Once I did this, it was as simple as reimporting them to our project and then performing motion matching with the updated assets.