On the user level spatial splits on hair BVH leads to very long build times,
without giving too much advantage in the render times.
There is also some issues and possibly bugs in the builder which lead to all
sort of numerical issues (like divisions by zero). There are also performance
issues that comes from the fact that the alignment space is applied every time
primitive's aligned bounds are requested. It also seems that the splitting
might not be considering aligned space consistently when calculating SAH and
performing splits.
It does sound like issues we'd get fixed ideally, but the importance of the
BVH2 is fading out with the HW-RT becoming more and more popular.
This change contains fix needed for the split algorithm to avoid numerical
issue reported by UBSAN when rendering the `BVH2 particle simple.blend` from
the #126508.
Ref #126508
Ref #136245
Pull Request: https://projects.blender.org/blender/blender/pulls/136430
b524d0fe39