Yes, very true. Or at least you can usually collapse. Memory is the issue, and collapsing multilevel doesn’t always fit.
There is some cost in the current hardware to multi-level traversal, that’s true. But still top & bottom terminology isn’t future-proof, doesn’t translate to CPU, and we might not be limited to 2-level GPU traversal forever. More to the point perhaps is that “top” and “bottom” aren’t words that describe the function. It’d be better to have terms that say what it does rather than where to find it, right?
Full disclosure, I work on OptiX. (But to be clear I literally have no idea if/when we might see multilevel traversal in hardware. I just happen to be in favor of seeing it someday, and if/when it does, TLAS and BLAS will become more awkward or get replaced.)
There is some cost in the current hardware to multi-level traversal, that’s true. But still top & bottom terminology isn’t future-proof, doesn’t translate to CPU, and we might not be limited to 2-level GPU traversal forever. More to the point perhaps is that “top” and “bottom” aren’t words that describe the function. It’d be better to have terms that say what it does rather than where to find it, right?
Full disclosure, I work on OptiX. (But to be clear I literally have no idea if/when we might see multilevel traversal in hardware. I just happen to be in favor of seeing it someday, and if/when it does, TLAS and BLAS will become more awkward or get replaced.)