Senior C# Developer

Lumion; Sassenheim; Hybrid; EUR 110,000 - 170,000; Full time

Job summary

Lumion is seeking a Senior C# Engineer to shape the scripting environment and bridge the native C++ core with a modern C# API. You will drive architecture choices, performance priorities, and the developer experience for our C# tooling.

Join a hybrid, international team delivering cutting-edge rendering and AI-driven features. You will collaborate across the C# team to evolve the scripting ecosystem from concept to production-ready deployment.

Qualifications

• Proven track record designing C# environments for high-performance apps.
• Deep experience with .NET 8/9+ and memory/perf optimization.
• Collaborative in hybrid team settings and able to shape vision from concept to production.

Responsibilities

• Evolve the Lumion scripting layer and make it a first-class citizen within the engine.
• Design and implement the interop layer and modern C# API bridging native C++ core.
• Drive memory management, serialization, and long-term stability of the C# environment.

Skills

C# architecture design

C# & C++ interop

C# tooling & ergonomics

Tools

Roslyn tooling

Job description

Lumion is redefining how architecture is communicated in the era of AI, from early concepts to final presentations. Our expanding portfolio helps architects, designers, and visualisation professionals communicate ideas with speed, clarity, and emotion, while making it easier for teams and stakeholders to collaborate around design.

We’re a passionate, international team of developers, designers, architects, and visualisation specialists looking to define how the AEC space collaborates on bringing design concepts to life. With a team across our Netherlands HQ, Denmark, Poland and a globally distributed remote workforce, we are at an exciting inflection point: new leadership, a growing product portfolio, and a market being rapidly reshaped by AI. The convergence of 3D rendering, real-time engines, and generative AI is accelerating, and we intend to lead it.

THE ROLE

We are seeking a Senior C# Engineer to join our team and serve as a foundational architect for our C# development environment. Working alongside our lead C# engineer, you will focus on evolving our scripting layer, transforming it into a high-performance, first-class citizen within the Lumion engine. You will play a pivotal role in defining the developer experience, performance characteristics, and long-term stability of the environment. You will drive the architecture from the ground up, designing the interop layer and API generators that bridge our native C++ core with a modern, idiomatic C# API. From memory management and serialization, you will help co-drive the technical roadmap that makes C# the premier environment for our developers.

WHAT YOU BRING

• A proven track record in designing C# environment architectures for high-performance applications, with deep expertise in .NET 8/9+ and low-allocation hot paths.
• A strong history of advocating for C# developer productivity, creating tools and APIs that prioritize ergonomics without sacrificing engine-level performance.
• The ability to work collaboratively within the C# team, helping to shape and execute the vision for the C# scripting environment from concept to production-ready deployment.

CORE COMPETENCIES

• API Design: Ability to create "idiomatic" C# interfaces that hide native complexity without sacrificing performance.
• Performance Profiling: Ability to use tools to identify bottlenecks in C# code and interop overhead.
• Compiler & Tooling Knowledge: Experience with Roslyn or similar build-time analysis tools is a major plus.

YOU’LL THRIVE HERE IF

• You enjoy "peeling the onion"—deconstructing complex, legacy systems and rebuilding them into clean, modern architectures.
• You value "Process, Not Outcome"—you appreciate technical depth and enjoy documenting the "why" behind design decisions.
• You are comfortable working in a hybrid environment where you influence both the low-level native engine code and the high-level application logic.
• You want to define the future of AEC software, where 3D rendering, real-time engines, and generative AI converge.