In this lesson, you will learn how to synchronize your character’s IK solvers and physics constraints to maintain a steady, grounded stance while riding rotating or translating platforms.
The Challenge of Moving Platforms
When a platform moves, your character’s capsule component often fails to perfectly match the platform's acceleration. If you rely solely on standard root motion or basic IK, your character might "drift" or jitter as the platform rotates or oscillates. To fix this, we must ensure our Full Body IK (FBIK) and procedural offsets are calculated relative to the platform's local space rather than the global world space.
Synchronizing Local Space Transformations
The secret to stability lies in transforming the platform’s velocity into the character's reference frame. By using Get Component Velocity on the platform and applying it as a procedural offset to your character's Pelvis control, you can counteract the platform's movement before the animation evaluates.
In your Animation Blueprint, you should capture the platform’s transformation and feed it into your Control Rig. Use a Modify Transform node inside your Rig to adjust the Pelvis height based on the platform's current surface normal:
// Logic conceptually applied in Control Rig
// Adjust foot IK targets based on platform surface tracking
FVector PlatformVelocity = MovingActor->GetVelocity();
PelvisControl.Location += (PlatformVelocity * DeltaTime);
Locking with Physics Constraints
If your character needs to feel truly "tethered" to a moving object, you can dynamically adjust the Physics Asset constraints while standing on the platform. By slightly increasing the stiffness of your Physical Animation Profiles when a Line Trace detects a dynamic object beneath the feet, you prevent the character from sliding off during sharp turns or sudden stops.
By combining the Full Body IK (to keep feet planted on moving geometry) with a Procedural Pelvis Offset (to counteract inertial drift), you create a seamless connection between the character’s base and the platform's transform. This ensures that even when the floor moves beneath you, your character remains centered and balanced.
Key Takeaway: To stabilize characters on moving platforms, always calculate your IK foot offsets and procedural pelvis adjustments in the platform’s local reference space to neutralize inertial drift.