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Avatar game feel: gaits matched to the ground, jump, camera collision, city interaction and audio #30

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opened 2026-08-10 07:07:28 +00:00 by jeroen · 1 comment

jeroen commented

2026-08-10 07:07:28 +00:00

Owner

The code is written. Eight commits sit on this branch; the ticket is the
record and the review handle, not a request to start.

Problem

The feet moved at half the speed of the ground, permanently. Input reaches
the display in one frame — a key press sets predicted_velocity and
smooth_online_avatar_display integrates it the same frame. What read as lag
was foot-slide, and it was arithmetic:

WALK_SPEED was 8.0 m/s and was the only speed — a world-class sprint
used for a stroll along a canal.
The Run clip is 0.8 s/cycle ≈ 4 m/s of real stride, played at a
hard-coded set_speed(1.0).
Walk (clip 22) was never loaded; the client knew only Idle (4) and Run (16).

Gravity was a constant 12 m/s descent with no acceleration in it, so
stepping off a kerb and falling off a tower began identically.

The motion constants existed in three private copies (sim, client
prediction, --offline path), each carrying a comment asking the next person to
keep them in step. A mismatch between the first two is invisible except as
rubber-banding; between the first and third the same key produces a different
world depending on how you launched.

The camera went through walls, had no reaction to a landing, and gave no
sense of pace.

Nothing streamed reacted to the avatar being near it. Picking was prim-only
and edit-oriented; benches and shops were scenery you walked through. The pois
and addresses layers were decoded on every streamed cell and thrown away — 467
and 6,211 features in the Groningen fixture
(docs/notes/vector-tile-unused-layers.md).

There was no audio at all. bevy_audio was dropped when the feature list
was slimmed. A city you can walk through in silence reads as a viewer, not a
place.

Approach

A shared speed model. crates/core/src/motion.rs holds what the sim, the
prediction and the offline path must agree on — sim_speed_for_wish (:40),
GRAVITY = 22.0 (:69, above Earth's so a jump does not hang like the moon)
and the integrated step_fall (:94). systems::locomotion holds the client's
half: stroll 1.4 / jog 4.2 / sprint 8.0 m/s
(crates/viberfox/src/systems/player/locomotion.rs:31,34,38) and the clip
reference speeds. Gaits cost nothing on the wire — apply_intent derives
speed from the wish vector's magnitude, so a gait is a magnitude the client
picks. Speed ramps in m/s² rather than easing a normalized throttle, or a sprint
start feels exactly as light as a walk start.

Clips matched to the ground. Walk is loaded, the gait is chosen by ground
speed with hysteresis, and playback rate is ground_speed / clip_reference_speed
so the stride covers the distance travelled. Changes cross-fade through
AnimationTransitions instead of stop/play.

Protocol 13 (crates/core/src/protocol.rs:56) for the two things that did
not fit through the magnitude throttle. ClientIntent::jump is a request the
sim grants only from the ground, so holding the bit cannot climb — a predicted
jump is reconciled straight into the floor, since SimWorld::step clamps
y >= 0. Emotes replicate as a level held on the wire for a couple of seconds
so a client arriving mid-wave sees it, which is why they carry a sequence number.

The follow boom collides in 2D and only below 15 m
(free_camera.rs:230) — footprints carry no height, so above an eaves line a 2D
hit means "there is a building over there", not "the view is blocked". In fast,
out slow, or every doorway makes the camera lunge. A landing dips the eye scaled
by impact speed; FOV widens toward a sprint. Driver mode is exempt.

The city answers back. crates/geo/src/places.rs extracts the two dropped
layers out of the TileData map_geometry already parses — no extra request,
no extra decode. systems::world_places keys them by cell in the anchored world
frame and drops them with the cell; systems::interact is the proximity prompt
and the E key. Street furniture becomes circle colliders.

Audio synthesised at startup (systems::soundscape) rather than shipped:
.gitattributes tracks audio by extension, so a shipped footstep would be an LFS
object with the documented silent-failure mode. Footsteps are counted off the
same ground speed that sets the clip rate, so they stay in phase by construction.

Acceptance criteria

Walk / jog / sprint are distinct speeds; Shift sprints, Alt strolls
The clip's playback rate tracks ground speed — no foot-slide at any gait
Gait changes cross-fade rather than popping
Space jumps from the ground and takes off if held past 0.25 s; the sim
grants it, so prediction is not reconciled into the floor
Falling is an integrated arc, identical in sim, prediction and --offline
1–6 play emotes, replicated so a client arriving mid-emote sees it
The follow camera does not pass through buildings below 15 m
Walking near a bench or a shop raises a prompt naming it; E acts on it
Street furniture is solid; the playground token is deliberately not
House numbers read out (numeric MVT values included — reading only
Value::String silently dropped most)
Footsteps, landings and wind play, all generated at startup
--no-default-features --features solo still builds on a host with no ALSA

Verification

Run in this container on 2026-08-10, all green:

cargo check --workspace                                   # clean
cargo test -p viberfox                                    # 284 passed
cargo test -p viberfox_geo --lib                          # 91 passed
cargo test -p viberfox_core                               # 23 passed
cargo check -p viberfox --no-default-features --features solo   # audio gate holds

New system prerequisite: the audio feature (on by default) pulls
bevy_audio → rodio → cpal → alsa-sys, whose build script panics without
libasound2-dev — it is a pkg-config shim with no vendored fallback. Any Linux
builder needs the package, or --no-default-features --features solo. Installed
in the agent container and added to its image definition on 2026-08-10.

Not verifiable here, needs a workstation: this container has no GPU and no
Vulkan ICD, so nothing was seen. The camera boom, the landing dip, the FOV
coupling, the flight/jump pose and the interaction prompt's placement are all
visually unchecked. cargo shots and a real walk around a city are the
missing gate.

Out of scope

Strafe and turn clips. The set contains Run_Left/Run_Right/Run_Back;
the avatar turns to face its wish direction instead, deliberately.
A flight clip. Quaternius has nothing airborne, and the UAL library's
cannot bind (different rig) — flight and jump are poses on the model
holders, not clips.
Animation events for footsteps. The clips carry none and adding them means
editing 20 glTFs; steps are counted from ground speed instead.
Server-side building collision. The sim holds no geometry; collision stays
client-side prediction against streamed footprints.
Terrain-aware collision. Footprints have no height, which is what gates the
camera test at 15 m and skips avatar collision while airborne.
Sound design beyond the three sources. No UI, ambience or vehicle audio.

Branch: feat/30-avatar-game-feel

Walking around the city read as "sluggish and unrealistic". The input path was not the cause, and neither was the network — this ticket covers the five things that actually were, plus the world-contact work that fell out of fixing them. **The code is written.** Eight commits sit on this branch; the ticket is the record and the review handle, not a request to start. ## Problem **The feet moved at half the speed of the ground, permanently.** Input reaches the display in one frame — a key press sets `predicted_velocity` and `smooth_online_avatar_display` integrates it the same frame. What read as lag was foot-slide, and it was arithmetic: - `WALK_SPEED` was **8.0 m/s** and was the *only* speed — a world-class sprint used for a stroll along a canal. - The `Run` clip is **0.8 s/cycle** ≈ 4 m/s of real stride, played at a hard-coded `set_speed(1.0)`. - `Walk` (clip 22) was never loaded; the client knew only Idle (4) and Run (16). **Gravity was a constant 12 m/s descent with no acceleration in it**, so stepping off a kerb and falling off a tower began identically. **The motion constants existed in three private copies** (sim, client prediction, `--offline` path), each carrying a comment asking the next person to keep them in step. A mismatch between the first two is invisible except as rubber-banding; between the first and third the same key produces a different world depending on how you launched. **The camera went through walls**, had no reaction to a landing, and gave no sense of pace. **Nothing streamed reacted to the avatar being near it.** Picking was prim-only and edit-oriented; benches and shops were scenery you walked through. The `pois` and `addresses` layers were decoded on every streamed cell and thrown away — 467 and 6,211 features in the Groningen fixture (`docs/notes/vector-tile-unused-layers.md`). **There was no audio at all.** `bevy_audio` was dropped when the feature list was slimmed. A city you can walk through in silence reads as a viewer, not a place. ## Approach **A shared speed model.** `crates/core/src/motion.rs` holds what the sim, the prediction and the offline path must agree on — `sim_speed_for_wish` (`:40`), `GRAVITY = 22.0` (`:69`, above Earth's so a jump does not hang like the moon) and the integrated `step_fall` (`:94`). `systems::locomotion` holds the client's half: stroll 1.4 / jog 4.2 / sprint 8.0 m/s (`crates/viberfox/src/systems/player/locomotion.rs:31,34,38`) and the clip reference speeds. Gaits cost **nothing on the wire** — `apply_intent` derives speed from the wish vector's *magnitude*, so a gait is a magnitude the client picks. Speed ramps in m/s² rather than easing a normalized throttle, or a sprint start feels exactly as light as a walk start. **Clips matched to the ground.** `Walk` is loaded, the gait is chosen by ground speed with hysteresis, and playback rate is `ground_speed / clip_reference_speed` so the stride covers the distance travelled. Changes cross-fade through `AnimationTransitions` instead of `stop`/`play`. **Protocol 13** (`crates/core/src/protocol.rs:56`) for the two things that did *not* fit through the magnitude throttle. `ClientIntent::jump` is a request the sim grants only from the ground, so holding the bit cannot climb — a predicted jump is reconciled straight into the floor, since `SimWorld::step` clamps `y >= 0`. Emotes replicate as a *level* held on the wire for a couple of seconds so a client arriving mid-wave sees it, which is why they carry a sequence number. **The follow boom collides in 2D and only below 15 m** (`free_camera.rs:230`) — footprints carry no height, so above an eaves line a 2D hit means "there is a building over there", not "the view is blocked". In fast, out slow, or every doorway makes the camera lunge. A landing dips the eye scaled by impact speed; FOV widens toward a sprint. Driver mode is exempt. **The city answers back.** `crates/geo/src/places.rs` extracts the two dropped layers out of the `TileData` `map_geometry` already parses — no extra request, no extra decode. `systems::world_places` keys them by cell in the anchored world frame and drops them with the cell; `systems::interact` is the proximity prompt and the E key. Street furniture becomes circle colliders. **Audio synthesised at startup** (`systems::soundscape`) rather than shipped: `.gitattributes` tracks audio by extension, so a shipped footstep would be an LFS object with the documented silent-failure mode. Footsteps are counted off the same ground speed that sets the clip rate, so they stay in phase by construction. ## Acceptance criteria - [x] Walk / jog / sprint are distinct speeds; `Shift` sprints, `Alt` strolls - [x] The clip's playback rate tracks ground speed — no foot-slide at any gait - [x] Gait changes cross-fade rather than popping - [x] `Space` jumps from the ground and takes off if held past 0.25 s; the sim grants it, so prediction is not reconciled into the floor - [x] Falling is an integrated arc, identical in sim, prediction and `--offline` - [x] `1`–`6` play emotes, replicated so a client arriving mid-emote sees it - [x] The follow camera does not pass through buildings below 15 m - [x] Walking near a bench or a shop raises a prompt naming it; `E` acts on it - [x] Street furniture is solid; the playground token is deliberately *not* - [x] House numbers read out (numeric MVT values included — reading only `Value::String` silently dropped most) - [x] Footsteps, landings and wind play, all generated at startup - [x] `--no-default-features --features solo` still builds on a host with no ALSA ## Verification Run in this container on 2026-08-10, all green: ``` cargo check --workspace # clean cargo test -p viberfox # 284 passed cargo test -p viberfox_geo --lib # 91 passed cargo test -p viberfox_core # 23 passed cargo check -p viberfox --no-default-features --features solo # audio gate holds ``` **New system prerequisite:** the `audio` feature (on by default) pulls `bevy_audio → rodio → cpal → alsa-sys`, whose build script *panics* without `libasound2-dev` — it is a pkg-config shim with no vendored fallback. Any Linux builder needs the package, or `--no-default-features --features solo`. Installed in the agent container and added to its image definition on 2026-08-10. **Not verifiable here, needs a workstation:** this container has no GPU and no Vulkan ICD, so nothing was seen. The camera boom, the landing dip, the FOV coupling, the flight/jump pose and the interaction prompt's placement are all **visually unchecked**. `cargo shots` and a real walk around a city are the missing gate. ## Out of scope - **Strafe and turn clips.** The set contains `Run_Left`/`Run_Right`/`Run_Back`; the avatar turns to face its wish direction instead, deliberately. - **A flight clip.** Quaternius has nothing airborne, and the UAL library's cannot bind (different rig) — flight and jump are *poses* on the model holders, not clips. - **Animation events for footsteps.** The clips carry none and adding them means editing 20 glTFs; steps are counted from ground speed instead. - **Server-side building collision.** The sim holds no geometry; collision stays client-side prediction against streamed footprints. - **Terrain-aware collision.** Footprints have no height, which is what gates the camera test at 15 m and skips avatar collision while airborne. - **Sound design beyond the three sources.** No UI, ambience or vehicle audio. --- Branch: `feat/30-avatar-game-feel`

jeroen added the

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label

2026-08-10 07:07:28 +00:00

viberfox-agent added this to the Viberfox project

2026-08-10 07:07:37 +00:00

jeroen commented

2026-08-10 12:39:45 +00:00

Author

Owner

Ready for review — branch feat/30-avatar-game-feel @ 28a9915.

PR: https://code.garage44.eu/jeroen/viberfox/compare/main...feat/30-avatar-game-feel

main moved three times while this was in flight (#28, #33, #35), so the branch
carries two merges of main. The one that mattered is #33, the POI-markers work:
it and this branch both read the tile's pois layer. Resolved by keeping both
modules — places answers "what can the avatar walk up to", pois answers "what
stands on the map" — with the reasoning in the merge commit and the note updated
to record three readers of one layer. Unifying them is a follow-up, not part of
this.

Also fixed here: the eight feature commits had never been through CI's fmt gate and
failed it at 14 sites (ef83f60). origin/main passes it clean, so they all
arrived with this work.

Verified on the merged tree

Gate	Result
`cargo fmt -p viberfox -p viberfox_geo -p viberfox_core -p viberfox_simulator -p viberfox_android --check`	OK
`cargo check --workspace --all-targets`	clean
`cargo test -p viberfox`	292 passed, 0 failed
`cargo test -p viberfox_geo`	95 passed
`cargo test -p viberfox_core`	23 passed
`cargo test -p big_space --lib`	14 passed

Not verified, and cannot be here

Nothing has been looked at. No GPU and no Vulkan ICD in the agent container,
so the camera boom, the landing dip, the FOV coupling, the flight/jump pose and
the interaction prompt's placement are unseen. cargo shots on a workstation is
the missing gate.
The Android check (no NDK here) and scene-smoke (no GPU).

New build prerequisite

The audio feature (default on) pulls bevy_audio -> rodio -> cpal -> alsa-sys,
whose build script panics without libasound2-dev — a pkg-config shim with no
vendored fallback. Any Linux builder needs the package, or
--no-default-features --features solo.

**Ready for review — branch `feat/30-avatar-game-feel` @ `28a9915`.** PR: https://code.garage44.eu/jeroen/viberfox/compare/main...feat/30-avatar-game-feel `main` moved three times while this was in flight (#28, #33, #35), so the branch carries two merges of `main`. The one that mattered is #33, the POI-markers work: it and this branch both read the tile's `pois` layer. Resolved by keeping both modules — `places` answers "what can the avatar walk up to", `pois` answers "what stands on the map" — with the reasoning in the merge commit and the note updated to record three readers of one layer. **Unifying them is a follow-up, not part of this.** Also fixed here: the eight feature commits had never been through CI's fmt gate and failed it at 14 sites (`ef83f60`). `origin/main` passes it clean, so they all arrived with this work. ### Verified on the merged tree | Gate | Result | |---|---| | `cargo fmt -p viberfox -p viberfox_geo -p viberfox_core -p viberfox_simulator -p viberfox_android --check` | OK | | `cargo check --workspace --all-targets` | clean | | `cargo test -p viberfox` | **292 passed**, 0 failed | | `cargo test -p viberfox_geo` | 95 passed | | `cargo test -p viberfox_core` | 23 passed | | `cargo test -p big_space --lib` | 14 passed | ### Not verified, and cannot be here - **Nothing has been looked at.** No GPU and no Vulkan ICD in the agent container, so the camera boom, the landing dip, the FOV coupling, the flight/jump pose and the interaction prompt's placement are unseen. `cargo shots` on a workstation is the missing gate. - The Android check (no NDK here) and `scene-smoke` (no GPU). ### New build prerequisite The `audio` feature (default on) pulls `bevy_audio -> rodio -> cpal -> alsa-sys`, whose build script panics without `libasound2-dev` — a pkg-config shim with no vendored fallback. Any Linux builder needs the package, or `--no-default-features --features solo`.