RTXPT is a high-fidelity real-time path tracing reference implementation developed by NVIDIA. It serves as both a standalone demo application and a reference for integrating advanced rendering techniques into production engines. The codebase implements state-of-the-art path tracing with ReSTIR (Reservoir Spatiotemporal Importance Resampling) for direct and global illumination, NEE-AT (Next Event Estimation - Adaptive Temporal) for lighting feedback, and Stable Planes for denoising. It integrates heavily with NVIDIA RTX SDKs including RTXDI, NRD (Denoiser), OMM (Opacity Micromaps), and DLSS (Streamline). The application supports both DirectX 12 and Vulkan backends via the nvrhi abstraction layer, though Vulkan support is noted as work-in-progress. The architecture follows a modular design with separate components for lighting bakers, material systems, shader compilation, and rendering passes. It uses the Donut engine framework for scene management and shader compilation infrastructure.