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.
OpenMoonRay is an open-source, production-grade path-tracing renderer developed by DreamWorks Animation and hosted under the Academy Software Foundation (ASWF). It is designed for feature film and VFX pipelines, supporting CPU and hybrid GPU (XPU) rendering, physically based materials, and integration with USD-based digital content creation tools via a Hydra render delegate. The system is composed of approximately 20 interconnected submodules covering core rendering, scene representation (RDL2), shaders (Moonshine), distributed computation (Arras), denoising, and more. Key entry points include the `moonray` CLI, `hd_render` for Hydra, `arras_render` for distributed rendering, and a Qt-based GUI (`moonray_gui`). The architecture is modular: the root repository orchestrates builds, provides test data, and houses build scripts and CI configurations, while the actual rendering logic resides in submodules. External dependencies include USD, OpenVDB, Embree, OpenImageDenoise, MaterialX, and Qt5, many of which require local patches for compatibility. The project is actively maintained with regular TSC meetings, CI workflows for Linux and macOS, and a growing open-source community.