Modern open-source C# .NET 10 Asheron's Call client. Faithful port of retail client behaviour to Silk.NET with a plugin API.
9e4772a8f8
Grounded player remotes were showing a ~5 Hz Z staircase when running
up/down slopes — the rate of server UpdatePositions. Body Z stayed flat
between UPs, then ramped over ~100ms during the queue-active chase to
each new server position, then went flat again until the next UP.
Diagnosis (no diagnostic needed — the math is unambiguous):
PositionManager.ComputeOffset has two modes via
InterpolationManager.AdjustOffset:
- Queue active (body chasing a waypoint): returns
`(head − body) / dist × min(catchUpSpeed × dt, dist)`. 3D direction,
Z follows server's reported Z naturally.
- Queue empty / head-reached (within DESIRED_DISTANCE = 0.05m of the
most recent UP): returns Vector3.Zero. ComputeOffset falls back to
`seqVel × dt rotated into world` — pure animation root motion. Every
locomotion cycle bakes Z=0 in body-local, so the world result has
Z=0 too. XY advances at the running pace; Z stays at the last UP.
For a runner at maxSpeed ≈ 4 m/s with catchUpSpeed = 2× = 8 m/s and
server UPs at ~5 Hz, body covers ~0.8m per UP, chases for ~100ms
(queue-active 3D path, Z ramps), then sits in seqVel-only mode for
~100ms (Z flat) until the next UP. Visible as a 5 Hz Z staircase.
Fix mirrors retail's CTransition::adjust_offset contact-plane projection
(named-retail acclient_2013_pseudo_c.txt:272296-272346) for grounded
motion, applied at the queue-empty boundary instead of inside the sweep:
PositionManager.ComputeOffset gains an optional Vector3? terrainNormal.
When the seqVel-only fallback runs AND a non-trivial terrain normal is
supplied, project rootMotionWorld onto the plane:
result = rootMotionWorld − N × dot(rootMotionWorld, N)
Anim XY motion gains a corresponding Z component proportional to slope
angle × forward speed, so body Z follows the terrain mesh between UPs.
No-op on flat ground (N ≈ +Z, dot ≈ 0); cannot regress L.3 M2's
flat-ground verification.
GameWindow.TickAnimations grounded-remote path samples
PhysicsEngine.SampleTerrainNormal at the body's current XY each tick
and passes it to ComputeOffset. SampleTerrainNormal is a thin public
wrapper over the existing internal SampleTerrainWalkable that returns
just the plane normal (no need to expose the internal sample shape).
Diagnostic: ACDREAM_SLOPE_DIAG=1 prints a per-tick [SLOPE] line with
guid, body Z before/after, offset, queue active flag, and the sampled
plane Nz so we can grep before/after the fix and confirm Z changes
continuously between UPs on slopes.
Tests: PositionManagerTests gains two cases:
- slope projection: 30° east-tilted plane, body running due east at
4 m/s for 1s → expect (3.0, 0, −1.732) (descends along slope, not
flat). Math: dot(seqVel, N) = 2.0 → result = (4,0,0) − (0.5,0,0.866)
× 2.0 = (3.0, 0, −1.732).
- flat-ground no-op: N = +Z, expect identical Y-only motion as the
pre-fix behavior.
Build green. 357 pass / 6 pre-existing fail (same set as
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| CLAUDE.md | ||
| README.md | ||
acdream
A modern open-source C# / .NET 10 Asheron's Call client.
Faithful port of the retail client's behaviour to Silk.NET with a modern, plugin-friendly architecture. The code is modern; the behaviour is retail.
Status: playable pre-alpha. You can log in to an ACE server, walk and run through Dereth, see other players animate correctly, watch the day-night cycle, hear ambient audio, and take weapons out. Many systems are still stubbed or in-progress — see roadmap.
Stack
- Language: C# .NET 10
- Graphics: Silk.NET (OpenGL 4.3)
- Audio: OpenAL via Silk.NET
- Dat parsing: Chorizite.DatReaderWriter
- Networking: Custom UDP + ISAAC cipher + game-message layer, wire-compatible with ACEmulator server
What works
- Connecting to a local ACEmulator (ACE) server on
127.0.0.1:9000 - Character selection and login
- Rendering Dereth terrain with retail-correct texture blending, per-vertex lighting, and road overlays
- Static scenery (buildings, trees, scenery objects) via EnvCell walker
- Animated characters (own + remote) with walk / run / strafe / jump / turn / attack motions sourced from the retail motion tables
- Network sync with remote players — you can watch other characters animate correctly, including speeds and directional motion
- Day-night cycle driven from the retail Region dat (0x13000000) — correct DayGroup picking via the retail LCG, correct keyframe interpolation, correct per-keyframe sky-object replace
- Weather (rain/snow particles synced from the server via the retail DayGroup name)
- Sky dome, stars, moon, clouds, sun — each rendered from the retail Region's SkyObjects with texture scrolling and alpha fade
- Plugin host with live event replay-on-subscribe
What's stubbed or in-progress
- Indoor transitions (building interiors) — disabled, Phase B.3 pending
- Combat — animation works, damage math not wired
- Lightning visual — the retail PhysicsScript-driven flash is researched
but not wired (see
docs/research/2026-04-23-lightning-real.md) - TimeSync drift — we only sync calendar on login, not periodically, so acdream's in-game clock gradually drifts from retail's
- Landscape draw distance — currently
ACDREAM_STREAM_RADIUS=2(~400m) vs retail's several kilometres
See docs/plans/2026-04-11-roadmap.md for the ordered phase list.
See docs/ISSUES.md for the rolling list of known bugs + small deferred
features (tactical, bug-level; the roadmap is strategic, phase-level).
Building + running
Requires:
- .NET 10 SDK
- A retail Asheron's Call dat directory (Turbine/Microsoft property —
supply your own). Contains
client_portal.dat,client_cell_1.dat,client_highres.dat,client_local_English.dat. - A running ACE (ACEmulator) server on
127.0.0.1:9000(or override via env var)
Launch (PowerShell on Windows — bash has trouble with the apostrophe in "Asheron's Call"):
$env:ACDREAM_DAT_DIR = "$env:USERPROFILE\Documents\Asheron's Call"
$env:ACDREAM_LIVE = "1"
$env:ACDREAM_TEST_HOST = "127.0.0.1"
$env:ACDREAM_TEST_PORT = "9000"
$env:ACDREAM_TEST_USER = "testaccount"
$env:ACDREAM_TEST_PASS = "testpassword"
dotnet run --project src\AcDream.App\AcDream.App.csproj -c Debug
Offline CLI dat inspector (no server needed):
dotnet run --project src/AcDream.Cli -- "C:\path\to\Asheron's Call"
Diagnostic env vars
| Variable | Effect |
|---|---|
ACDREAM_DUMP_SKY=1 |
Per-second dump of the interpolated SkyKeyframe values + per-SkyObject draw info + texture alpha histograms |
ACDREAM_DUMP_MOTION=1 |
Dump every inbound UpdateMotion + resulting SetCycle |
ACDREAM_STREAM_RADIUS=N |
Tune landblock visible-window radius (default 2 = 5×5) |
ACDREAM_NO_AUDIO=1 |
Suppress OpenAL init |
ACDREAM_DAY_GROUP=N |
Force a specific DayGroup index for A/B-testing weather presets |
ACDREAM_RUN_SKILL=N / ACDREAM_JUMP_SKILL=N |
Client-side run/jump skill (default 200) |
Layout
src/
AcDream.App/ rendering + audio + main loop (Silk.NET)
AcDream.Core/ game state, meshing, physics, sky, weather, lighting
AcDream.Core.Net/ UDP + ISAAC + game-message layer
AcDream.Cli/ offline dat-inspector console app
AcDream.Plugin.Abstractions/ plugin host interfaces
AcDream.Plugins.Smoke/ example plugin
tests/
AcDream.Core.Tests/ xUnit tests (742 passing)
AcDream.Core.Net.Tests/ network-layer tests
tools/
RetailTimeProbe/ Win32 P/Invoke ReadProcessMemory probe of
the live retail acclient.exe — dumps
TimeOfDay + sky-lighting globals so we
can compare against acdream's state
SkyObjectInspect/ dat-inspector for Region sky objects
references/ vendored read-only reference code — ACE,
ACViewer, WorldBuilder, holtburger,
AC2D, Chorizite, DatReaderWriter.
Gitignored.
docs/
architecture/ single-source-of-truth architecture doc
plans/ phase roadmaps + per-phase specs
research/ decompile-derived research, per-phase
findings, deep-dive agent reports
audit/ phase-completion audits
Development workflow
All AC-specific behaviour is ported from the decompiled retail client
(docs/research/decompiled/). The workflow is:
- Decompile first. Find the matching function in the decompiled client.
- Cross-reference. Check against ACE's C# port and ACViewer / WorldBuilder.
- Write pseudocode. Translate C to readable pseudocode first.
- Port faithfully. Translate line-by-line, preserving variable names and control flow.
- Conformance test. Add tests using golden values from retail.
- Integrate surgically. Minimise churn in the surrounding pipeline.
Guessing at AC-specific algorithms is explicitly forbidden — see
CLAUDE.md for the full workflow rationale and the list of failure
modes we've paid for in the past.
Reference repos
We cross-reference five external projects for every retail behaviour:
- ACE (ACEmulator) — authoritative server-side protocol
- ACViewer — MonoGame dat viewer; good for character appearance
- WorldBuilder — Silk.NET dat editor; matches our stack
- Chorizite.ACProtocol — clean-room C# protocol library
- holtburger — most complete non-retail client; Rust TUI, full client-side behaviour
- AC2D — C++ AC-client emulator; has the real terrain split formula and 0xF61C movement packet format
See CLAUDE.md for which reference is authoritative for which domain.
Licence
Not yet chosen. All external reference code is vendored under its own
licence; see references/*/LICENSE. The acdream source code itself is
unreleased — not yet distributed to the public. Once the licence
choice is made it will go in a top-level LICENSE file.
The AC dat files and the game's intellectual property remain the property of Microsoft / Turbine. This project does not distribute any of those files or assets — you must supply your own retail install.