Hi,
A bit behind the curve (senior moment thing), but I was bumbling along with (obviously) with the 2nd Edition (don’t ask how/why) and I was looking at Chap 21 (MPS) and looking at my sources (for the 4th edition) and I was confused. Sure, I now have the 2nd edition sources, but my main question is why that entire section on Ray Tracing in the MPS chapter (Edition 2) seems to have been deleted by Edition 3 (and later editions). Was it moved? Is the code/techniques no longer valid? I ask because it looks like some of the things covered in the Ray Tracing section are interesting in stuff I’m working on.
Apple first introduced Ray Tracing in MPS (Metal Performance Shaders), but they redesigned it at WWDC 2020. It’s now a huge topic worthy of its own book, so wouldn’t fit in the Metal by Tutorials book any more.
This is the API documentation: Ray tracing with acceleration structures | Apple Developer Documentation
Also, in 2023, the iPhone got hardware-accelerated ray tracing, so it’s much faster on modern devices.
The final chapters of 3rd edition contain the theory of basic ray tracing through compute shaders, but no Apple API. I removed them from the 4th edition to make room for other improvements, such as Mesh shaders. But the code from the 3rd edition won’t have changed, because it was all GPU-side.
Thanks for the quick response. I appreciate it.
I did (finally) notice that all that ray tracing stuff was excised with the 3rd edition.
So, any plans for a RT tutorial? Some of us might benefit for being hand-held through examples (instead of slogging through an API spec) 
Unfortunately not in the very near future. I won’t say never, because I always have plans. But don’t hold your breath!