server::lagcomp Namespace Reference

Pure (dependency-free) lag-compensation rewind math. More...

Functions
constexpr std::uint32_t	msToTicks (std::uint32_t ms, std::uint32_t tickRateHz)
	Round a millisecond duration to the nearest whole physics tick.
std::uint32_t	computeRewindTicks (std::uint16_t rttMs, std::uint16_t interpDelayMs, std::uint8_t interpDelaySnapshots, std::uint32_t snapshotEveryNTicks, std::uint32_t tickRateHz, std::uint32_t maxLagCompTicks)
	Compute the lag-compensation rewind depth (in physics ticks) for a shooter from their last-reported net state.

Detailed Description

Pure (dependency-free) lag-compensation rewind math.

Lives in its own header so it can be unit-tested in isolation — ServerGame includes it from the hot path in updateLagCompTargets.

Function Documentation

computeRewindTicks()

std::uint32_t server::lagcomp::computeRewindTicks ( std::uint16_t rttMs, std::uint16_t interpDelayMs, std::uint8_t interpDelaySnapshots, std::uint32_t snapshotEveryNTicks, std::uint32_t tickRateHz, std::uint32_t maxLagCompTicks )

inline

Compute the lag-compensation rewind depth (in physics ticks) for a shooter from their last-reported net state.

PR-31: prefer the client's measured render delay in milliseconds (interpDelayMs, derived client-side from an EMA of observed snapshot-apply intervals) whenever it is non-zero. The measured value tracks the real snapshot cadence — including the drift introduced by a highly jittery link and the post-join warm-up window before the EMA converges — so the server rewinds to exactly the render time the client actually displayed when it fired.

Falls back to the legacy snapshot-count estimate (interpDelaySnapshots × snapshotEveryNTicks) when interpDelayMs == 0, i.e. render-delay interpolation is disabled (cl_interp 0) or the client predates the ms field. That path uses the server's nominal fixed cadence, which can diverge from the client's true render delay under jitter — exactly the mismatch the ms field eliminates.

The combined RTT + interp depth is clamped to maxLagCompTicks so the rewind never exceeds the HitboxHistory ring.

Parameters

rttMs	Client's smoothed full round-trip time (ms).
interpDelayMs	Client's measured render delay (ms); 0 selects fallback.
interpDelaySnapshots	Client's render delay in snapshots (fallback term).
snapshotEveryNTicks	Server's nominal physics-ticks-per-snapshot.
tickRateHz	Physics tick rate.
maxLagCompTicks	Upper clamp (= HitboxHistory ring depth).

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msToTicks()

std::uint32_t server::lagcomp::msToTicks ( std::uint32_t ms, std::uint32_t tickRateHz )

inlineconstexpr

Round a millisecond duration to the nearest whole physics tick.

Integer-only round-to-nearest via (ms * Hz + 500) / 1000.

Note

ms is taken as uint32 so the multiply can't overflow for any uint16 wire value (65535 × 1000 Hz still fits uint32).

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