feat/player-movement

Serkyo commented

2026-08-22 03:03:11 +00:00

Owner

What does this PR do?

Implements an end-to-end, server-authoritative, client-predicted player movement system over the voxel terrain with reconciliation and camera smoothing.

An exhaustive breakdown of every change made in this branch across all crates and subsystems:

1. Core Collision & Voxel Query (`crates/shared`)

Block Extent Conventions (world::bounds): Centralized half-open block extent arithmetic ([i, i + 1)) so floor inverts extents consistently across collision, meshing, and culling.
VoxelQuery Trait (movement::query): Added spatial query abstraction returning Option<BlockId> where None indicates an unloaded chunk (treated as a solid obstacle rather than air to prevent falling through the void).
AABB Colliders & Stances (movement::collider): Defined player bounding boxes across three stances according to ADR 0012 (Standing: 0.75×1.75 m, Crouching: 0.75×1.25 m, Crawling/Sliding: 0.75×0.75 m).
Swept AABB Collision (movement::sweep): Substepped, axis-separated collision resolution in fixed order (X, Y, Z) with blocker classification (Blocker::Solid, Blocker::Unloaded).
Attempt-and-Revert Step-Up (movement::sweep): Clear low obstacles up to 1.2 voxels (0.6 m) by attempting elevated forward displacement and reverting to ground-level sweep if blocked.

2. Deterministic Locomotion Controller (`crates/shared`)

Fixed Timestep: Evaluates physics at a fixed 60 Hz rate (dt = 1/60s) without variable delta time.
Tuned Movement Profile (movement::profile): Configured locomotion ladder speeds (Sneak: 1.5 m/s, Walk: 4.0 m/s, Run: 6.0 m/s, Sprint: 8.5 m/s, Slide initial: 10.0 m/s), gravity (32 m/s²), jump apex times, and stance heights.
Dedicated Deceleration Ramp: Separate 90 u/s² ground deceleration rate so speed is shed quickly upon releasing input or downshifting gaits instead of coasting.
Air Control & Wall Momentum: Clamped air control preserving horizontal momentum during airborne wall contact (clearing velocity only while grounded).
Coyote Time: Grace window for jumping when running off slopes or ledges.
Downhill Ground Following (snap_to_ground): Downward snap (1 voxel) to maintain ground contact when descending stepped slopes.
Committed Slide Refinements: Lengthened slide travel downhill, slide cancellation into run upon releasing crouch key, and slide termination when colliding with solid geometry (>10% horizontal speed loss).
Stance Refusal Rules: Prohibits standing up if ceiling clearance is insufficient.
Traversal Events (movement::state): Emits discrete events for footstep pacing, jumps, landings, fall distance tracking, and slide state transitions.
Precision Coordinate Math (world::entity): Added EntityPos::delta subtracting integer chunk anchors before f32 conversion for precision at large distances.

3. Prediction & Reconciliation Engine (`crates/shared`)

Prediction Ring Buffer (movement::prediction): Fixed 60-tick ring buffer storing unacknowledged (InputFrame, MovementState) pairs with wrapping sequence tick comparisons (tick_is_newer) and overflow protection.
Reconciliation Engine (movement::reconcile): Compares authoritative snapshots against local prediction buffer. Checks motion/stance match, position distance (1 cm squared threshold), and velocity error.
State Rewind & Replay: On divergence, replays all buffered unacknowledged ticks forward from the authoritative state.
Unloaded Stall Flag: Returns halted_unloaded flag in StepOutcome to inform client/server if movement stopped due to chunk streaming boundaries.

4. Networking & Protocols (`crates/net`, `crates/shared`)

QUIC Stream Purpose Tagging (net::runtime): Added one-byte stream layout tags to prevent acceptor races across multi-stream connections.
Dedicated Input Stream (net::input): Carries client InputFrame payloads with sequence ticks, 2D normalized movement vectors, and held/pressed action bitfields.
Dedicated Authority Stream (net::authority): Streams authoritative PlayerState snapshots with full movement state and last acknowledged client tick.
Protocol Version Bump: Incremented PROTOCOL_VERSION to 4 for full movement state serialization.

5. Authoritative Server Architecture (`crates/server`)

Per-Session Player Management (server::player): Spawns and tracks player entities per active connection.
Surface Spawn Scan: Origin column raycasting against world bounds to place spawning players safely on top of terrain.
Authoritative Tick Execution (server::main): Steps movement controller at 60 Hz against chunk stores exposed as VoxelQuery.
Idempotent Input Queue (PendingInput): Ingests input frames by tick, rejecting duplicate, late, or already-simulated frames.

6. Client Prediction, Input & Presentation (`crates/client`)

Fixed-Rate Input Sampling (client::input): 60 Hz input sampler with latched keypresses and swapped sprint/sneak keybinding fix.
Redundant Input Packet Transmission: Sends current tick with a tail of the last 4 unacknowledged frames (REDUNDANT_FRAMES = 4) to withstand packet loss.
Client Prediction System (client::prediction): Local simulation against client chunk storage with replay reconciliation.
Camera Mounting & Eye Interpolation (client::camera): Decoupled mouse-look from movement tick; mounts eye at predicted position with tick interpolation fraction (alpha).
Render-Only Camera Smoothing:
- Exponential decay (~50 ms) for visual position error correction (< 1.0 m) avoiding visual teleports.
- Symmetric stair-step climbing and descent smoothing (~100 ms) preventing jarring eye dips across blocky terrain.
Debug & Telemetry (client::debug, client::stats): Added prediction metrics to overlay (pred line) and F1 + P keybinding to test desync recovery via artificial 3-block displacement.

7. Documentation & Housekeeping

ADR 0012 (docs/adr/0012-player-collider-dimensions.md): Formally recorded player collider dimensions, stance boxes, and half-scale units.
ADR 0002 & Architecture Map Updates (docs/): Updated documentation cross-references.
Codebase Cleanliness: Reorganized file-level constant declarations to the top of files across client, renderer, shared, and test suites.

Why is this change necessary?

Prior to this PR, the client used a free-fly debug camera with no collision, physics, or network synchronization. This PR establishes the core movement foundation:

Zero Input Latency: Local prediction provides instantaneous feedback for player movement actions.
Server Authority & Anti-Cheat: Physics and movement authority reside entirely on the server; client input cannot forge positions or bypass collision.
Smooth Voxel Traversal: Half-scale voxels (0.5 m) inherently create stepped inclines. Automated step-ups, ground snapping, substepping, and visual stair smoothing eliminate snagging, clipping, and camera jitter on stepped terrain.

Scope of Changes

client, server, networking, renderer, shared, workspace

Testing

Automated Test Suite:
- cargo test --workspace fully passing (344 tests total):
  - shared (186 tests): Swept AABB collision, substepping limits, step-up clearance & reversion, stance ceiling refusal, downhill ground snapping, momentum conservation on air wall contact, deceleration ramps, slide collision deflection & cancellation, coyote time, prediction ring buffer lifecycle & wrapping, exact replay reproducibility on divergence.
  - client (74 tests): Input sampling, latched keypress edges, prediction buffer queueing, stair climb/descent camera smoothing without eye dips.
  - server (42 tests): Input queue idempotency, player spawn raycasting, authority replication.
  - net (27 tests): Stream purpose framing, input/authority serialization codecs.
  - renderer (14 tests): Mesh updates and rendering statistics.
Static Analysis & Linting:
- cargo fmt --all -- --check clean.
- cargo clippy --all-targets --all-features -- -D warnings clean.
Manual / In-Game Verification:
- Verified movement gaits (sneak, walk, run, sprint, jump, slide) across varied terrain.
- Confirmed smooth step-up/down stair traversal with camera interpolation.
- Injected artificial position desyncs via F1 + P to confirm smooth exponential convergence back to server authority.

Additional Context

Deterministic Architecture: All physics simulation logic lives in crates/shared/src/movement/ as pure functions of (state, input, profile, world). The exact same simulation runs on both client and server.
Split-Coordinate Safety: Position difference arithmetic (EntityPos::delta) computes chunk anchor integer deltas first to avoid float precision loss far from origin.
Strict Visual/Physical Separation: Camera smoothing and step offsets only affect the rendered view and are never fed back into the physics collider or state buffer.
Future Work (Out of Scope):
- Remote player entity interpolation and ghost rendering (focus of this PR is local player prediction).
- Swimming, climbing/mantling, stamina systems, and per-block friction physics (tracked in subsequent feature cards).

No response

Checklist

I have branched from dev (or a feature branch off dev) and my PR targets dev.
I have kept my changes focused to a single concept.
I have added or updated documentation (/// doc comments for Rust) where necessary.
I have tested my changes and described any relevant automated or manual testing above.

### What does this PR do? Implements an end-to-end, server-authoritative, client-predicted player movement system over the voxel terrain with reconciliation and camera smoothing. An exhaustive breakdown of every change made in this branch across all crates and subsystems: ### 1. Core Collision & Voxel Query (`crates/shared`) - **Block Extent Conventions (`world::bounds`)**: Centralized half-open block extent arithmetic (`[i, i + 1)`) so `floor` inverts extents consistently across collision, meshing, and culling. - **`VoxelQuery` Trait (`movement::query`)**: Added spatial query abstraction returning `Option<BlockId>` where `None` indicates an unloaded chunk (treated as a solid obstacle rather than air to prevent falling through the void). - **AABB Colliders & Stances (`movement::collider`)**: Defined player bounding boxes across three stances according to ADR 0012 (Standing: 0.75×1.75 m, Crouching: 0.75×1.25 m, Crawling/Sliding: 0.75×0.75 m). - **Swept AABB Collision (`movement::sweep`)**: Substepped, axis-separated collision resolution in fixed order (X, Y, Z) with blocker classification (`Blocker::Solid`, `Blocker::Unloaded`). - **Attempt-and-Revert Step-Up (`movement::sweep`)**: Clear low obstacles up to 1.2 voxels (0.6 m) by attempting elevated forward displacement and reverting to ground-level sweep if blocked. ### 2. Deterministic Locomotion Controller (`crates/shared`) - **Fixed Timestep**: Evaluates physics at a fixed 60 Hz rate (`dt = 1/60s`) without variable delta time. - **Tuned Movement Profile (`movement::profile`)**: Configured locomotion ladder speeds (Sneak: 1.5 m/s, Walk: 4.0 m/s, Run: 6.0 m/s, Sprint: 8.5 m/s, Slide initial: 10.0 m/s), gravity (32 m/s²), jump apex times, and stance heights. - **Dedicated Deceleration Ramp**: Separate 90 u/s² ground deceleration rate so speed is shed quickly upon releasing input or downshifting gaits instead of coasting. - **Air Control & Wall Momentum**: Clamped air control preserving horizontal momentum during airborne wall contact (clearing velocity only while grounded). - **Coyote Time**: Grace window for jumping when running off slopes or ledges. - **Downhill Ground Following (`snap_to_ground`)**: Downward snap (1 voxel) to maintain ground contact when descending stepped slopes. - **Committed Slide Refinements**: Lengthened slide travel downhill, slide cancellation into run upon releasing crouch key, and slide termination when colliding with solid geometry (>10% horizontal speed loss). - **Stance Refusal Rules**: Prohibits standing up if ceiling clearance is insufficient. - **Traversal Events (`movement::state`)**: Emits discrete events for footstep pacing, jumps, landings, fall distance tracking, and slide state transitions. - **Precision Coordinate Math (`world::entity`)**: Added `EntityPos::delta` subtracting integer chunk anchors before `f32` conversion for precision at large distances. ### 3. Prediction & Reconciliation Engine (`crates/shared`) - **Prediction Ring Buffer (`movement::prediction`)**: Fixed 60-tick ring buffer storing unacknowledged `(InputFrame, MovementState)` pairs with wrapping sequence tick comparisons (`tick_is_newer`) and overflow protection. - **Reconciliation Engine (`movement::reconcile`)**: Compares authoritative snapshots against local prediction buffer. Checks motion/stance match, position distance (1 cm squared threshold), and velocity error. - **State Rewind & Replay**: On divergence, replays all buffered unacknowledged ticks forward from the authoritative state. - **Unloaded Stall Flag**: Returns `halted_unloaded` flag in `StepOutcome` to inform client/server if movement stopped due to chunk streaming boundaries. ### 4. Networking & Protocols (`crates/net`, `crates/shared`) - **QUIC Stream Purpose Tagging (`net::runtime`)**: Added one-byte stream layout tags to prevent acceptor races across multi-stream connections. - **Dedicated Input Stream (`net::input`)**: Carries client `InputFrame` payloads with sequence ticks, 2D normalized movement vectors, and held/pressed action bitfields. - **Dedicated Authority Stream (`net::authority`)**: Streams authoritative `PlayerState` snapshots with full movement state and last acknowledged client tick. - **Protocol Version Bump**: Incremented `PROTOCOL_VERSION` to 4 for full movement state serialization. ### 5. Authoritative Server Architecture (`crates/server`) - **Per-Session Player Management (`server::player`)**: Spawns and tracks player entities per active connection. - **Surface Spawn Scan**: Origin column raycasting against world bounds to place spawning players safely on top of terrain. - **Authoritative Tick Execution (`server::main`)**: Steps movement controller at 60 Hz against chunk stores exposed as `VoxelQuery`. - **Idempotent Input Queue (`PendingInput`)**: Ingests input frames by tick, rejecting duplicate, late, or already-simulated frames. ### 6. Client Prediction, Input & Presentation (`crates/client`) - **Fixed-Rate Input Sampling (`client::input`)**: 60 Hz input sampler with latched keypresses and swapped sprint/sneak keybinding fix. - **Redundant Input Packet Transmission**: Sends current tick with a tail of the last 4 unacknowledged frames (`REDUNDANT_FRAMES = 4`) to withstand packet loss. - **Client Prediction System (`client::prediction`)**: Local simulation against client chunk storage with replay reconciliation. - **Camera Mounting & Eye Interpolation (`client::camera`)**: Decoupled mouse-look from movement tick; mounts eye at predicted position with tick interpolation fraction (`alpha`). - **Render-Only Camera Smoothing**: - Exponential decay (~50 ms) for visual position error correction (< 1.0 m) avoiding visual teleports. - Symmetric stair-step climbing and descent smoothing (~100 ms) preventing jarring eye dips across blocky terrain. - **Debug & Telemetry (`client::debug`, `client::stats`)**: Added prediction metrics to overlay (`pred` line) and **F1 + P** keybinding to test desync recovery via artificial 3-block displacement. ### 7. Documentation & Housekeeping - **ADR 0012 (`docs/adr/0012-player-collider-dimensions.md`)**: Formally recorded player collider dimensions, stance boxes, and half-scale units. - **ADR 0002 & Architecture Map Updates (`docs/`)**: Updated documentation cross-references. - **Codebase Cleanliness**: Reorganized file-level constant declarations to the top of files across `client`, `renderer`, `shared`, and test suites. ### Why is this change necessary? Prior to this PR, the client used a free-fly debug camera with no collision, physics, or network synchronization. This PR establishes the core movement foundation: 1. **Zero Input Latency**: Local prediction provides instantaneous feedback for player movement actions. 2. **Server Authority & Anti-Cheat**: Physics and movement authority reside entirely on the server; client input cannot forge positions or bypass collision. 3. **Smooth Voxel Traversal**: Half-scale voxels (0.5 m) inherently create stepped inclines. Automated step-ups, ground snapping, substepping, and visual stair smoothing eliminate snagging, clipping, and camera jitter on stepped terrain. ### Scope of Changes client, server, networking, renderer, shared, workspace ### Testing - **Automated Test Suite**: - `cargo test --workspace` fully passing (344 tests total): - **`shared` (186 tests)**: Swept AABB collision, substepping limits, step-up clearance & reversion, stance ceiling refusal, downhill ground snapping, momentum conservation on air wall contact, deceleration ramps, slide collision deflection & cancellation, coyote time, prediction ring buffer lifecycle & wrapping, exact replay reproducibility on divergence. - **`client` (74 tests)**: Input sampling, latched keypress edges, prediction buffer queueing, stair climb/descent camera smoothing without eye dips. - **`server` (42 tests)**: Input queue idempotency, player spawn raycasting, authority replication. - **`net` (27 tests)**: Stream purpose framing, input/authority serialization codecs. - **`renderer` (14 tests)**: Mesh updates and rendering statistics. - **Static Analysis & Linting**: - `cargo fmt --all -- --check` clean. - `cargo clippy --all-targets --all-features -- -D warnings` clean. - **Manual / In-Game Verification**: - Verified movement gaits (sneak, walk, run, sprint, jump, slide) across varied terrain. - Confirmed smooth step-up/down stair traversal with camera interpolation. - Injected artificial position desyncs via **F1 + P** to confirm smooth exponential convergence back to server authority. ### Additional Context - **Deterministic Architecture**: All physics simulation logic lives in `crates/shared/src/movement/` as pure functions of `(state, input, profile, world)`. The exact same simulation runs on both client and server. - **Split-Coordinate Safety**: Position difference arithmetic (`EntityPos::delta`) computes chunk anchor integer deltas first to avoid float precision loss far from origin. - **Strict Visual/Physical Separation**: Camera smoothing and step offsets only affect the rendered view and are never fed back into the physics collider or state buffer. - **Future Work (Out of Scope)**: - Remote player entity interpolation and ghost rendering (focus of this PR is local player prediction). - Swimming, climbing/mantling, stamina systems, and per-block friction physics (tracked in subsequent feature cards). ### Related Issues _No response_ ### Checklist - [x] I have branched from `dev` (or a feature branch off `dev`) and my PR targets `dev`. - [x] I have kept my changes focused to a single concept. - [x] I have added or updated documentation (`///` doc comments for Rust) where necessary. - [x] I have tested my changes and described any relevant automated or manual testing above.

Serkyo added 42 commits

2026-08-22 03:03:12 +00:00

docs(workspace): record the player collider dimensions as an ADR ba535b8548

feat(shared): centralise the block extent convention 05c67eac4d

feat(shared): add the voxel query trait and block coordinate helpers 8ca043ef64

feat(shared): add the player collider and stance dimensions 2647c95c92

feat(shared): resolve swept collider motion against the voxel field 0f54335a6c

feat(shared): clear low obstacles with an attempt-and-revert step-up 4b775f20dc

feat(shared): add the movement profile and the fixed simulation timestep ce05b1cb98

feat(shared): add the movement input tick and its world-space intent 14dcc8d397

feat(shared): add the movement state and the ground stance machine c5486a57b5

feat(net): tag opened streams with their layout purpose 9e6ccf0a7c

feat(shared): add the locomotion ladder and its ramped acceleration 316811c2e8

feat(shared): add gravity, the jump set, and clamped air control f6ca934c74

feat(shared): add the ground stance machine and its refusal rules 2755c71c23

feat(shared): add the committed slide and its recovery into a crawl e961f26348

feat(shared): add fall tracking and the traversal event list f98ddf8273

feat(shared): add the input-stream frame and its action bitfield e9c03e9c19

feat(net): carry sampled player input on its own tagged stream 3679a36b8e

feat(server): spawn one player entity per connected session 03b193cb8a

feat(server): expose both chunk stores to the collider as VoxelQuery 94c2217bd0

feat(server): step the movement controller in a live tick schedule b383548487

feat(shared): replicate the authoritative character state each tick e720b42b63

feat(client): sample input on a fixed tick with latched presses 71da05bcfc

feat(client): mount the camera on the authoritative character position 0c6f55b0fb

feat(shared): expose the terrain surface bounds from the worldgen config 8220d90027

fix(server): spawn on the surface instead of inside the terrain 7607b0a067

fix(client): swapped the keys for sprinting and sneaking 773ef38248

feat(shared): add coyote time for slope jumping 86b625367a

feat(shared): return the unloaded-stall flag from a controller step 46bdcc1da3

feat(shared): move the wire-to-controller intent conversion onto the frame 86afbfc893

feat(shared): replicate the full controller state for replay 6577bba9f2

feat(shared): add the prediction ring buffer for unacknowledged input 44c97b38e1

feat(shared): detect prediction divergence and replay the unacknowledged tail 934f8ecbca

feat(server): apply input frames idempotently by tick 93e8e23bad

feat(client): predict movement locally and reconcile it against authority dd13497dde

fix(client): stop the render eye interpolating across a smoothed step df0d41cd06

fix(shared): give ground deceleration its own ramp so speed is not coasted off 467232edfc

fix(shared): keep horizontal momentum through an airborne wall contact 4ac6c0d35f

fix(shared): tune gravity and the charged jump to the design note's figures 7d9d2e2f3a

feat(shared): follow stepped ground downhill and lengthen the slide c543fd68bc

fix(shared): end a slide that meets geometry instead of deflecting it 28c9951022

feat(shared): let a crouch release stand a slide up into a run 97f45c6608

refactor(workspace): declare file-level constants at the top of their files

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📝 CLA Signature Required

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### 📝 CLA Signature Required @Serkyo — thank you for your contribution! Before this pull request can be reviewed and merged, all commit authors must sign the [Contributor License Agreement](https://github.com/Synvael/synvael/blob/dev/CLA.md). To sign, please leave a comment on this pull request containing **exactly**: ``` I have read the CLA and I agree ``` Signing is a one-time action. Once recorded, all future pull requests from the same account are accepted automatically.

Serkyo added 1 commit

2026-08-22 03:52:58 +00:00

chore(renderer): use as_chunks instead of chunks_exact in meshing tests

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Merge branch 'dev' into feat/player-movement

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2026-08-22 05:31:56 +00:00

Merge branch 'dev' into feat/player-movement

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Serkyo merged commit 7ae22d6c66 into dev

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Serkyo referenced this pull request from a commit

2026-08-22 05:56:54 +00:00

Merge pull request 'feat/player-movement' (#2) from feat/player-movement into dev

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Columns

feat/player-movement #2

What does this PR do?

1. Core Collision & Voxel Query (crates/shared)

2. Deterministic Locomotion Controller (crates/shared)

3. Prediction & Reconciliation Engine (crates/shared)

4. Networking & Protocols (crates/net, crates/shared)

5. Authoritative Server Architecture (crates/server)

6. Client Prediction, Input & Presentation (crates/client)

7. Documentation & Housekeeping

Why is this change necessary?

Scope of Changes

Testing

Additional Context

Related Issues

Checklist

📝 CLA Signature Required

1. Core Collision & Voxel Query (`crates/shared`)

2. Deterministic Locomotion Controller (`crates/shared`)

3. Prediction & Reconciliation Engine (`crates/shared`)

4. Networking & Protocols (`crates/net`, `crates/shared`)

5. Authoritative Server Architecture (`crates/server`)

6. Client Prediction, Input & Presentation (`crates/client`)