补充输入重放

输入重放是指当收到一个服务器状态包时以那个包为初始状态，然后重新计算所有未确认的输入来得到当前帧的状态，然后再对当前角色的位置进行插值移动。服务器状态包只能给出前几帧的权威数据，而当前帧的状态则需要通过输入回放来得到
2026-04-08 10:33:42 +08:00
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+# local-player-presentation-state Specification
+
+## Purpose
+
+Define how the local player's presentation layer holds current display state and smoothly interpolates toward the simulation layer's target state each frame.
+
+## ADDED Requirements
+
+### Requirement: Presentation layer holds current and target state
+
+The local player's presentation layer SHALL maintain `_currentPosition` and `_currentRotation` (the actively displayed state) separately from `_targetPosition` and `_targetRotation` (the simulation layer's output).
+
+#### Scenario: Presentation state initializes from first simulation target
+- **WHEN** the presentation layer is initialized or first receives a simulation target
+- **THEN** `_currentPosition` and `_currentRotation` are set equal to the initial target
+- **THEN** subsequent updates lerp toward the target
+
+### Requirement: Presentation layer lerps toward target each frame
+
+The presentation layer SHALL each frame interpolate `_currentPosition` and `_currentRotation` toward `_targetPosition` and `_targetRotation` using linear interpolation, then apply the result to the Rigidbody.
+
+#### Scenario: Lerp position and rotation toward target
+- **WHEN** the presentation layer updates each frame with interpolation alpha α
+- **THEN** `_currentPosition` is updated to `Vector3.Lerp(_currentPosition, _targetPosition, α)`
+- **THEN** `_currentRotation` is updated to `Quaternion.Slerp(_currentRotation, _targetRotation, α)`
+- **THEN** `_rigid.position` and `_rigid.rotation` are set to `_currentPosition` and `_currentRotation`
+
+### Requirement: Presentation layer snaps when target error exceeds threshold
+
+When the distance between `_currentPosition` and `_targetPosition` exceeds the snap threshold, the presentation layer SHALL immediately snap `_currentPosition` to `_targetPosition` without lerping.
+
+#### Scenario: Snap when error exceeds threshold
+- **WHEN** `Vector3.Distance(_currentPosition, _targetPosition) > SnapThreshold`
+- **THEN** `_currentPosition` is set equal to `_targetPosition`
+- **THEN** `_currentRotation` is set equal to `_targetRotation`
+- **THEN** no lerping occurs in this frame