Intel software engineers have released version 0.7 of Open PGL, their open-source Path Guiding Library (PGL) that can be used by 3D renderers to enjoy state-of-the-art path guiding methods for better sampling quality and efficiency.

Open PGL is part of Intel's oneAPI Rendering Toolkit and can allow for some very nice results while being Apache 2.0 licensed and delivering great visual quality and performance:

Open PGL is used by Blender and other software. Open PGL 0.7 delivers new experimental features of Radiance Caching (RC), Guided/Adjoint-driven Russian Roulette (GRR), and Image-space guiding buffer (ISGB). Open PGL's radiance caching support in particular should be nice for helping with performance. There are also a number of API improvements, new optimizations, bug fixes, and also having initial support for Windows on ARM.

Downloads and more details on Open PGL v0.7 via GitHub .