Article 4 (on refitting) and 5 (constructing BLAS + TLAS) should arrive this week, completing the basic C++ implementation of the algorithm used for DXR / RTX.
I skimmed through the series last night and enjoyed it. It's a nice basic overview so far and will be handy to point to for anyone who wants to learn the basics of this stuff. I look forward to seeing the rest of it.
As I didn't know what the BVH is, from the first, OP linked article: In this series we explore the wonderful world of the bounding volume hierarchy: the mysterious data structure that enables real-time ray tracing on recent GPUs, in complex, animated scenes. Despite the broad adoption of ray tracing in games, in-depth understanding of the underlying technology seems to be reserved to a select few. In this article we show how a proper BVH is implemented without support from DXR / RTX / OptiX / Vulkan, in easy-to-read ‘sane C++’.