perf(input): stop sending CharacterMoveInputEvent every idle tick - #5381
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#4993: LocalPlayerSystem.processInput() sent a CharacterMoveInputEvent every single tick regardless of whether the player was providing any input, creating a lot of unnecessary events and debug-log noise. ## Why the obvious fix wasn't safe KinematicCharacterMover only applies gravity (GRAVITY * movementComp.mode.scaleGravity) inside step(), which only runs when a CharacterMoveInputEvent is processed - so a naive "return early if nothing changed" (as originally proposed on the issue) would leave an idle local player floating in place instead of falling, e.g. if a block were removed underfoot. This dependency is exactly what skaldarnar's comment on the issue guessed at. ## Why it's safe anyway ServerCharacterPredictionSystem.update() (@RegisterSystem(AUTHORITY), so this runs for single-player and any host, which is what #4993's own report exercises) already has a "haven't received input in a while, repeat last input" fallback: every TIME_BETWEEN_STATE_REPLICATE (50ms), it checks whether the buffered state has fallen more than MAX_INPUT_UNDERFLOW (100ms) behind game time, and if so synthesizes a continuation CharacterMoveInputEvent from the last real input (with an updated deltaMs) and re-steps physics with it. This was almost certainly built for network-jitter tolerance, but it equally covers "the local player stopped sending input" - gravity keeps ticking at a worst-case ~100-150ms cadence regardless, well below the threshold of being noticeable, and self-corrects every replication cycle either way. Also checked: CharacterMoveInputEvent.sequenceNumber has no contiguity requirement (ClientCharacterPredictionSystem only compares it with <=, to drop already-acknowledged inputs), and the server reconstructs elapsed idle time from its own wall clock rather than from anything the client sends, so skipped sends don't create a "lost time" gap when input resumes. ## Fix processInput() now tracks whether the last sent event was itself a "nothing happening" tick (sentIdleInput) and skips sending again while that stays true - i.e. it always sends the *first* idle tick (giving the server's fallback a state to continue from) and any tick with real movement/look/jump input or a run/crouch toggle change, but suppresses the identical repeats in between. Losing window focus still resets the idle marker, so the very next focused tick always sends, regardless of what it finds. ## Verification :engine:compileJava and :engine-tests:compileTestJava both clean. LocalPlayerSystem has no existing test coverage (needs a live input pipeline, display and camera, not something unit-testable in isolation), so this is root-caused and fixed by tracing the actual gravity/replication code paths, not by observing a running game. Fixes #4993 Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
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ChangesLocal player input handling
Estimated code review effort: 2 (Simple) | ~10 minutes Merge Risk: ⚪ Minimal · up to The change suppresses repeated idle movement events while preserving the first idle tick and active input updates; no actionable merge-blocking risk remains, so it is merge-ready after normal checks. Poem
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In
`@engine/src/main/java/org/terasology/engine/logic/players/LocalPlayerSystem.java`:
- Around line 114-121: Reset sentIdleInput in onPlayerSpawn() before invoking
update(0), so idle-event suppression does not carry over from the previous
character entity and the new entity receives its initial
CharacterMoveInputEvent.
- Around line 164-171: Update processInput() to track the last sent absolute
lookPitch and lookYaw values, and include changes from those values in the
suppression predicate alongside lookYawDelta and lookPitchDelta. In the
successful CharacterMoveInputEvent send path, update lastSentLookPitch and
lastSentLookYaw so absolute view changes are transmitted once without
suppressing subsequent idle inputs.
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engine/src/main/java/org/terasology/engine/logic/players/LocalPlayerSystem.java
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Two gaps in the idle-suppression logic from the previous commit, both caught by review: - onPlayerSpawn() called update(0) without resetting sentIdleInput, so a respawned character (new entity) could inherit "already sent idle" from the previous character and have its first-ever event suppressed, never registering with the server's characterStates/ lastInputEvent tracking. - setRotation() (SetDirectionEvent) sets lookPitch/lookYaw directly, bypassing lookPitchDelta/lookYawDelta entirely - the suppression check only looked at the deltas, so a SetDirectionEvent arriving while otherwise idle could be silently dropped. Reset the idle marker on spawn, and track the last-sent absolute pitch/yaw alongside the deltas so a direct view change is detected too. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
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Fixes #4993 -
LocalPlayerSystem.processInput()sent aCharacterMoveInputEventevery single tick regardless of whether the player was providing any input, creating a lot of unnecessary events and debug-log noise.This is reasoned from tracing the gravity/replication code paths (see below), not from observing a running game - I don't have a GL context available here. The one behavior actually worth double-checking by hand: stand a local-player character still (no keys, no mouse movement) somewhere it should fall - e.g. dig out the block underneath, or spawn over a pit - and confirm it still falls promptly instead of hovering. My reading says
ServerCharacterPredictionSystem's existing ~100-150ms "repeat last input" fallback covers this, but that fallback was written for network-jitter tolerance, not for this case, and I can't rule out some interaction I haven't seen. If it turns out to hover, the fix needs to go back to decoupling gravity fromCharacterMoveInputEventdirectly rather than leaning on that fallback.Why the obvious fix wasn't safe
KinematicCharacterMoveronly applies gravity (GRAVITY * movementComp.mode.scaleGravity) insidestep(), which only runs when aCharacterMoveInputEventis processed - so a naive "return early if nothing changed" (as originally proposed on the issue) would leave an idle local player floating in place instead of falling, e.g. if a block were removed underfoot. This dependency is exactly what skaldarnar's comment on the issue guessed at.Why it's safe anyway
ServerCharacterPredictionSystem.update()(@RegisterSystem(AUTHORITY), so this runs for single-player and any host, which is what #4993's own report exercises) already has a "haven't received input in a while, repeat last input" fallback: everyTIME_BETWEEN_STATE_REPLICATE(50ms), it checks whether the buffered state has fallen more thanMAX_INPUT_UNDERFLOW(100ms) behind game time, and if so synthesizes a continuationCharacterMoveInputEventfrom the last real input (with an updateddeltaMs) and re-steps physics with it. This was almost certainly built for network-jitter tolerance, but it equally covers "the local player stopped sending input" - gravity keeps ticking at a worst-case ~100-150ms cadence regardless, well below the threshold of being noticeable, and self-corrects every replication cycle either way.Also checked:
CharacterMoveInputEvent.sequenceNumberhas no contiguity requirement (ClientCharacterPredictionSystemonly compares it with<=, to drop already-acknowledged inputs), and the server reconstructs elapsed idle time from its own wall clock rather than from anything the client sends, so skipped sends don't create a "lost time" gap when input resumes.Fix
processInput()now tracks whether the last sent event was itself a "nothing happening" tick (sentIdleInput) and skips sending again while that stays true - i.e. it always sends the first idle tick (giving the server's fallback a state to continue from) and any tick with real movement/look/jump input or a run/crouch toggle change, but suppresses the identical repeats in between. Losing window focus still resets the idle marker, so the very next focused tick always sends, regardless of what it finds.Verification
:engine:compileJavaand:engine-tests:compileTestJavaboth clean.LocalPlayerSystemhas no existing test coverage (needs a live input pipeline, display and camera, not something unit-testable in isolation), so this is root-caused and fixed by tracing the actual gravity/replication code paths, not by observing a running game.