Got any gameplay video to show your setup / what you’re dealing with?
Always an interesting topic… Those who’ve slain Root Motion in Multiplayer probably know all the secrets, as it likely requires a large rewrite of the CMC (for multiplayer especially). The core problem is, UE4 + UDK treat characters on a moving platform like an obstacle (similar to being outside the front of the ship blocking travel). So even if you work around the problem with some ‘glue’, there’s always other use cases to trip you up (including what happens if the character needs to jump etc).
Because of that I think removing collision on the character completely is the way to go. Instead implementing some form of alternative collision detection and manual movement. So manually controlling walking / jumping anims and movement, and then either attaching the player mesh to the ship to sync movement or updating it cleverly behind the scenes to keep everything in sync without rubber banding / blurring. A custom collision system could use live-tracing / overlaps / predictive movement to handle characters bumping into each other or the hull. Ship control interaction could be done using the WIC etc.
The problem with AFF style Render-Texture is that it works well for AFF, but for other games just getting RT to accurately match the rendered Viewport is a challenge, before even dealing with all the performance side-affects. Clearly its the easiest solution to fake the effect though. Moving the whole world around the ship would help resolve origin rebasing issues which would be great too obviously. But OR has its own performance issues. There are a few other threads on this iirc, but I don’t think any of them ever nailed it. Star Citizen may offer some useful insights. I forget what its called, but its like a nested physics volume (where the inside of the ship has completely different physics to the outside). However, they both live side-by-side, so the inside movement and custom gravity doesn’t fight the outside ship movement or gravity, because you don’t want two or more opposing movement or force systems, or you get all the problems you see in UE4 / UDK.