Expand description
Snapshots each simulated body’s world-space transform into the engine’s
[TransformInterpolation] store so the render path can interpolate between
the prior and current GlobalTransform for smooth motion at any frame
rate.
Runs in TickPhase::PostSimulation before transform_propagation
(lower order_hint): it captures the still-current GlobalTransform — the
value produced by the previous frame’s propagation — before propagation
overwrites it with this frame’s simulated pose. Render then blends
previous → current by the Time::interpolation_alpha.
The snapshots live in Runtime::resources, NOT in
the ECS: interpolation is a render-only representation (“adapt the HOW,
never the WHAT”), so it carries no game meaning and must not appear in the
editor inspector or scene files. Only simulated entities (those carrying a
RigidBody) are snapshotted; everything else renders at its current
transform.