I wrote this last year. Enjoy.
http://www.codercorner.com/ZeroByteBVH.pdf
As usual, the bitcoin tip jar is here if you like what you read 
EDIT:
“Any sufficiently advanced technology is indistinguishable from magic”
If a game uses PhysX, it does not mean you will notice it. It might not have obvious PhysX effects in it. It might not have cloth, or PhysX particles, or water effects, etc.
These are just flashy/trendy effects that are easy to advertise/sell/etc for the marketing people. The kind of stuff that gamers care about, maybe. But this is not the important part.
The most important part is the one that you don’t see. The one that makes you game playable at all.
When you fire a gun in a FPS, that’s PhysX (”raycast single” scene queries).
When NPCs/AI see you, that’s PhysX (”raycast any” scene queries).
When many NPCs properly interact and avoid going through each-other, that’s PhysX (broadphase).
When your character simply moves in the level, that’s PhysX (”sweep” scene queries, or even PhysX’s character controller).
It’s not just about ragdolls or particle effects. PhysX is also there supporting the invisible foundation upon which everything else is built.