Editing Animations in UE5 - Clayton Jetton

Our game's goal for multi-state omnidirectional player locomotion requires a lot of work on animations. This has been a big learning experience considering I am not formally trained as an animator, nor was I extensively familiar with Unreal's animation tools at the start of this process. Things are progressing well now, but there were certainly a lot of hiccups that I imagine other novice animators / animation programmers will run into, so I'll try to talk about them in the order that I ran into them.

* Control Rig: Control rigs are a type of Unreal asset that helps facilitate the editing of animations by creating "controls" for bones that can be transformed and keyed. These controls are very modular and have a lot of options, like gizmo customization, that makes the editor's user experience a lot better. Control rigs also allow you to edit animations through IK bones which makes the whole process feel a lot more natural. Despite these nice features, I found myself having to abandon the use of control rig assets for several reasons.

1. Control rigs are complicated to build with no experience. By default, most skeletons do not come with a control rig asset, and the process of building controls for every bone in a skeleton, and also reversing the process to read the values of those controls is daunting for a control rig novice with limited time.
2. Control rigs introduce virtually undiagnosable issues into animations. The biggest time waster I experienced while using control rig assets was the experience that you can spend hours editing an animation in control rig, it looks good in the level sequencer, it looks good in the animation sequence preview, it looks good in the animation blueprint preview, but then in the PIE it looks completely different. I was never able to find the source of this issue, and this is what ultimately led me to the following alternative.

3. FK Control Rigs just work! An alternative to building your own control rig asset is having the engine auto-generate an FK control rig. As denoted by the name, the obvious drawback to this rig type is that it's not intended for editing with IK bones, but I would argue that that's not really a big deal because most of what you need to do with IK bones is handled on the programming side anyways. Since transitioning to this tool, after a brief learning curve, I have had a consistent and productive experience editing animations in Unreal.

* Post-Process Animation Blueprints: Some high-quality skeletal meshes, like the Unreal mannequin, have a post-process animation blueprint that handles the mesh's corrective bones. Corrective bones are extra bones on a skeleton whose sole purpose is to keep the mesh's skin from become distorted due to overstretched bones. Without these corrective bones, a mesh can end up looking stretched or twisted like a "candy wrapper". You must be careful to disable these blueprints when editing animations on these kinds of meshes, because when you bake changes to corrective bones those changes are additive. This can have an exponential effect of multiplying these corrective bones' key values until they are sticking out far from their original positions. So if you ever find that your mesh has pointy joints during certain animations, the post-process blueprint is probably the culprit, or more accurately you are the culprit for not disabling it.

* Additive Animations: Understanding how and when to use additive animations was a total game-changer for getting comfortable editing animations. I would honestly recommend this workflow to anyone trying to get into editing animations in Unreal:

1. Pick a "base animation" that you already like, but just need to make some changes to for your specific game's purposes.

2. Duplicate the base animation.

3. Bake the duplicate animation to an FK control rig

4. Turn off the post process blueprint on the mesh.

5. Attach any props you need to the skeleton for reference / move the mesh if in bad position (this does not mean edit bones)

6. Add an additive track to the control rig.

7. Auto key changes.

8. Ensure you are only editing the first frame of the animation.

9. Rotate bones until you have the desired pose.

2. Transition Priority: In state machines every transition has a priority. Let's say from your walking forward state, you have transitions to stop walking forward and a transition to start walking in another direction. Well the conditions for these things happening may be true at the same time, but if you want to walk in another direction, you don't want to stop and then start. You just want to start. So you give the start higher priority than the stop. Problem solved.