Resume

Reuben Dunnington: Systems Programmer

Empathetic, intrinsically motivated generalist. Building performant, scalable systems across teams and disciplines.

Professional Experience

• Developed technical interview process for systems engineers and made key hires. Cross-team systems eng meeting, driving quality, performance, scaling, and identifying problems with systems, process, and workflow.
• Led development on a Mass-based NPC spawn/despawn system featuring multi-agent patrols with editor and runtime tooling and visualization. Character cap and intelligent despawn to control perf without loss of NPCs.
• Created and drove Unreal upgrade process, coordinating stakeholders across the studio to ensure minimal disruption. "Smoothest engine upgrade I've seen in my career" - Principal Tech Artist Matt Canei.
• Created optimization plan highlighting effort-to-reward. Implemented character and replication optimizations, bringing single-threaded server frametime down from 54.97ms avg (141ms max) to 21.83ms avg (62ms max).
• Championed and drove debug menu adoption across the studio. Integrated and modified Imgui to work seamlessly in a client-server environment.
• Custom OSS git source control solution for Unreal. UGS parity with game/engine syncing for content creators. Rust-based external tooling. OFPA name translation. Optimizations for Unreal plugin bringing ops from 20s to 0.5s, and batched locking 1000x faster in DynamoDB (1500s to 1.5s).
• From-scratch OSS code testing framework, with Slate UI test runner. Code tests have native coroutine support. Unit, "world", and client-server tests for guaranteeing replicated behavior.
• OpenTelemetry library integration and OSS plugin featuring spans, metrics, and events. Built-in editor, map, and PIE load timing observability.
• Mentored interns, junior, and senior engineers. No gameplay or systems experience to effective Unreal C++ developers in ~6 months. Code reviews, “mob” programming, and quick feedback loops to accelerate learning.

• Identified and optimized both code and data sources of Unreal game thread perf problems across a variety of different systems. Champion for workflow iteration times, improving PIE performance from 45ms down to 15ms, map load times from 5+ mins to ~30s, and out-of-process PIE startup times from 30+ mins to ~1 min.
• Wrote custom tooling and debug systems to support content creators' specific needs around animation, world building, audio (Wwise), and gameplay systems. Extended existing Unreal systems with new UI and hotkeys.
• Owned the full stack of NPC AI, locomotion, and animation systems, implementing behavior tree-driven, designer-tweakable, custom movement abilities synced with animation in a networked environment.
• Extended the Houdini Engine for Unreal plugin to leverage native landscape spline curves for procgen roads.
• Champion for test automation, extending the native Unreal framework to simplify writing tests, creating multiple code and BP-oriented tests to lead by example, and integrated them with our automated Jenkins pipeline.
• Leveraged Unreal replication and RepGraph, minimizing net traffic while providing a compelling real-time, debuggable experience on the client for gameplay systems such as destruction and AI-oriented functionality.
• Fixed crashes and critical bugs in various engine-level systems, such as World Partition, Level Instances, UObject, Navigation, Input, Animation, and Gameplay Ability System.

• Ported Slipspace engine, tools, and CI to prerelease Xbox Series X hardware, OS, and SDK. Worked closely with the platform team providing kernel and SDK feedback, testing, and bug reports. Managed rollout to 500+ people.
• Aggressively profiled and optimized memory for many systems in different parts of the engine, saving hundreds of megs that allowed the memory-constrained Xbox One title to ship and increasing Mean-Time-To-Failure over 4x (46.6 to 197.6 mins).
• Owned all engine-level memory APIs, creating new in-engine and standalone tools for memory analysis, improving existing tracking features, and hooking telemetry support for continuous integration visiblity.
• Profiled and implemented optimizations for major perf bottlenecks in the asset pipeline's asset metadata system, in some cases shaving hours off nightly build times.
• Upgraded tools, asset pipeline, and infrastructure to support external studios. Enabled multiple codevelopment partners to be able to work on code and assets worldwide, which before would have been impossible.

• Discovered and executed CPU and memory optimization opportunities in client code, including a new custom Lua memory profiler and content tools that shaved over 40% of overall memory usage and cut load times in half.
• Designed and implemented NoSQL-based systems capable of unlimited horizontal scaling in a live environment.
• Created an automatic server-based hot-reload system for Lua to enable quick iteration on mobile devices.
• Full stack engineer for gameplay. UI/UX, gameplay logic, node.js backend, redis and rethinkdb storage.
• Mentored junior engineers, increasing their independence and spreading knowledge of in-house systems.

• Led engineering development from inception through closed beta with excellent KPIs, resulting in an external evaluation projection of $30 million gross revenue over 1 year.
• Co-designed and integrated data analytics and A/B testing solutions in collaboration with publisher requirements to discover, analyze, and resolve user experience problems and increase retention and revenue.
• Implemented many crucial game features including core loop battle system, UI prototypes, and data pipelines.
• Collaborated closely with designers on tutorial, iterating quickly on publisher feedback for greenlight milestones.
• Mentored remote engineer new to the project, providing feedback and building their connection with the team.

• Gathered publisher requirements, achieving milestones for data analytics, ads, and in-app messaging.

• Integrated Scaleform's full technology stack including custom renderer, ActionScript interop, and input on multiple platforms to meet milestone requirements, gameplay programmer needs, and UX design aspirations.
• Invented a custom localization solution that integrated tightly with inhouse tools, streamlining designer workflows while reducing localization costs.

• Added and polished features on engine and gameplay systems, optimizing the game on 3DS to run at 30 FPS.
• Owned and improved designer tool workflows. Fixed an “impossible” tools bug that cost countless man-hours.

• Implemented features, fixed bugs, and improved stability for a critical E3 demo a month after joining the team.
• Closely collaborated with artists to realize their UI vision throughout the game on multiple platforms.

• Single-handledly shipped the universal version of the game, adding iCloud save and other bugfixes.

• Implemented gameplay features and designer-oriented editing tools that tightly integrated with Unity.

• Independently brought the entire project from inception to ship within two months.

• Supported and added major features, polished UX, and met inhouse needs for a Vala IDE plugin for Gedit.

Open Source Experience

• Major contributor to the Orca project, a development platform and runtime environment for cross-platform, sandboxed graphical applications.
• Implemented a full C standard library implmentation in terms of Orca APIs to provide a familiar programming environment for C programmers.
• Provided a complete set of idomatic API bindings to the Zig programming langugage.
• Replaced raw calls to wasm3 with a custom wasm layer that allows for easy compile-time switching between wasm backends.
• Platform layer work fixing bugs and bringing Windows to parity with MacOS.

• Primary author and maintainer of Bytebox, a from-scratch WebAssembly interpreter written in Zig, capable of running in standalone mode or embedded as a library.
• Fully compliant with the WASM 2.0 spec.
• Implemented WASI Preview 1 support, an extension that allows WebAssembly programs to interact with objects outside it's sandbox via IO.
• Debugging interface supports single-stepping, and tracing per-function or per-instruction.
• C FFI interface for use in other languages.

Education