Highly Performant & Scalable Ultima Online Server Emulator
https://www.modernuo.com
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Splits creature speed into two clocks so movement pace can be tuned without touching reaction time: - **Think clock** — `ActiveSpeed`/`PassiveSpeed`/`CurrentSpeed`: seconds per AI decision. Unchanged in meaning, storage, and cadence. - **Move clock** — `ActiveMoveSpeed`/`PassiveMoveSpeed` (+ resolved `CurrentMoveSpeed`): seconds per step. `0` = inherit the matching think value. ### How - Move speeds come from optional `activeMove`/`passiveMove` in `npc-speeds.json`, are `[props`-tunable per instance (set `0` to re-inherit), and serialize (BaseCreature v22). - `SetSpeed()` keeps its legacy one-clock semantics — sets the think clock **and clears move overrides** — so existing callers cannot half-configure a creature. `SetMoveSpeed()`/`ClearMoveSpeed()` configure movement explicitly; `ScaleMoveSpeed()` scales overrides for buffs. - `CurrentMoveSpeed` is derived by classifying `CurrentSpeed`: a verbatim active/passive think value maps to the matching move value; a bespoke pace written directly (mount boosts, follow sprint) stays fused to both clocks. External `CurrentSpeed` writers need no changes. - `AITimer` schedules the earlier of the two deadlines. Decisions run at the think cadence exactly as before; while a pursuit/investigation is live, the timer also wakes when the movement budget elapses and advances one step with no decisions. Steps no longer snap to the think grid, so any step delay paces smoothly on the 8ms wheel. A blocked creature schedules no move wakes. - The movement budget is RunUO's `m_NextMove` accumulate-and-clamp at a full step, so long-run pacing averages `CurrentMoveSpeed` exactly. ### Behavior changes - **`npc-speeds.json` buckets get RunUO `TransformMoveDelay`-parity move values**: creatures step at RunUO pace while thinking/reacting at current speed. The situational +0.1/+0.2 offsets are deliberately omitted. - **Existing saves migrate on load**: a pre-v22 creature whose think speeds still match its npc-speeds entry (never hand-tuned) adopts the table's move values — worlds and pets pick up the new pacing without a respawn. Tuned creatures keep movement inheriting their think clock. - **Paragons scale movement by `SpeedBuff` (1.2x)**: RunUO had no deliberate policy here — dividing by 1.2 knocked most speeds off `TransformMoveDelay`'s exact-equality table (raw pass-through, 2x+ faster), while 0.3/0.6 creatures landed back on it for ~1.33x. This applies the uniform 1.2x the buff always claimed. UnConvert snaps speeds back to exact table values within 1e-4 — /1.2 then ×1.2 drifts 0.45 and 0.9 by an ulp, which would read as hand-tuned (and defeat a future skip-table-conformant-values serialization pass); tuned speeds keep. - **Herding paces the movement clock**: the old `CurrentSpeed` getter hack is gone. A herded creature walks at a fixed 0.3s/step — RunUO's forced pace, without its `TransformMoveDelay` inflation to 0.6 — so herding is never penalized by a slow creature. Thinking is untouched, and `CheckHerding` walks through `MoveToPoint`, so herded creatures path around obstacles. - **Badly-hurt slowdown now inflates the step delay only** (RunUO parity), computed from the base each step. Previously it wrote `CurrentSpeed = CurrentSpeed + 0.05..0.15` back on every successful step — compounding unboundedly while hurt and slowing decisions too. - Removes the vestigial `MoveSpeedMod` (never read, written, or serialized). - With no bucket or per-instance move values, both clocks carry identical values and creatures pace as before. ### Testing - Full suite passes (1557, including 12 new `MoveSpeedTests`: resolution classes, `SetSpeed` clearing, `0`-re-inherit, v22 round-trip with exact-consumption check, save migration adopt/skip, buff scale/snap, herding). - In-game verified via local diagnostics build (per-step budget tracing): steady 700ms step cadence on a 0.3s think grid with one-step catch-up after idle, think grid unperturbed by move wakes. |
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| Distribution/Data | ||
| Projects | ||
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| .cursorrules | ||
| .editorconfig | ||
| .gitattributes | ||
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| AGENTS.md | ||
| azure-pipelines.yml | ||
| CLAUDE.md | ||
| CODE_OF_CONDUCT.md | ||
| CONTRIBUTING.md | ||
| Directory.Build.props | ||
| FAQ.md | ||
| GEMINI.md | ||
| global.json | ||
| LICENSE | ||
| ModernUO.slnx | ||
| publish.cmd | ||
| publish.ps1 | ||
| publish.sh | ||
| README.md | ||
| rider-settings.zip | ||
| Rules.ruleset | ||
| SPONSORS.md | ||
| stylecop.json | ||
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| version.json | ||
ModernUO 
Ultima Online Server Emulator for the modern era!
Requirements
Supported Operating Systems
Required Frameworks
All Operating Systems
Windows
Hardware
| Use | vCPU | RAM | Storage |
|---|---|---|---|
| Development / test | 2 dedicated | 2 GB | SSD |
| Small live shard (< 50 concurrent) | 4 dedicated | 4 GB | NVMe |
| Medium (50–200) | 4–8 | 8 GB | NVMe |
| Large (200+) | 8+, high clock | 16 GB+ | NVMe |
See dev-docs/server-requirements.md for more information.
Development
Supported IDEs
Getting Started
- Install prerequisite requirements
- Clone this repository (or download the latest):
git clone https://github.com/modernuo/ModernUO.git
- Open
ModernUO.slnto start developing
Building/Publishing
Interactive Mode (Recommended for new users)
Run ./publish.cmd (Windows) or ./publish.sh (Linux/macOS) with no arguments to launch the guided build tool. It will:
- Check prerequisites (.NET SDK, native libraries)
- Walk you through configuration and platform selection
- Build and publish the server to the
Distributiondirectory - Show deployment instructions for cross-compiled builds
Command Line
./publish.cmd [release|debug] [os] [arch]
os- Supported operating systemsarchx64- Intel/AMD 64-bitarm64- ARM 64-bit
Linux Prerequisites
Fedora, CentOS, RHEL, AlmaLinux, Rocky, etc
dnf upgrade --refresh -y
# RHEL-family distributions (CentOS Stream, AlmaLinux, Rocky, RHEL) need CRB and EPEL enabled.
# Fedora skips this block.
dnf install -y dnf-plugins-core
dnf config-manager --set-enabled crb
dnf install -y epel-release
# Prerequisites
dnf install -y findutils libicu libdeflate libargon2 tzdata
Ubuntu, Debian, etc
apt-get update -y
# The ICU runtime package carries the ABI version in its name (libicu74, libicu76, …) and has no
# stable alias, so match it by pattern rather than pinning a release-specific name.
apt-get install -y '^libicu[0-9]+$' libdeflate0 libargon2-1 tzdata
Only the runtime libraries are needed — the -dev/-devel packages are not. Run
./build-tool --check-prereqs to check the current machine and print the exact packages your
release needs.
zstd is not listed because ZstdNet bundles libzstd for every platform, and liburing is not
listed because IORingGroup issues io_uring syscalls directly.
If the shard's configured time zone is a legacy alias such as US/Eastern, Debian 12 and Ubuntu
24.04 also need tzdata-legacy. See Platform Prerequisites
for what each dependency is for and what breaks without it.
OSX Requirements
brew install icu4c libdeflate argon2
Running the Server
- Follow the publish instructions
- The
Distributiondirectory is portable — copy it to your production server for deployment - Run
ModernUO.exeordotnet ModernUO.dllfrom theDistributiondirectory - On first run, the server will prompt you to configure game data file locations
Troubleshooting / FAQ
- See FAQ
Want to sponsor?
Thank you for supporting us! You can find out how by visiting the sponsors page.
Collaborators
Thanks
- RunUO Team & Community
- Voxpire, the ServUO Team & Community
- Karasho, Jaedan and the ClassicUO Community
Development Tools & Plugins provided with ♥ by
Code Signing Policy
Free code signing provided by SignPath.io, certificate by SignPath Foundation.
This program will not transfer any information to other networked systems unless specifically requested by the user or the person installing or operating it
Teams & Roles
Approvers & Committers: Development Team