the code snippet is supposed to compute the maximal `isect.t` in the
array, which is used to determine if subsequent intersections should be
added.
However, the previous implementation includes the old `isect.t` which is
going to be replaced, resulting an overestimation of `tmax_hits` and
thus missing closer intersections.
For BVH2, the issue is fixed by computing the `max_t` after a new entry
is inserted.
For Embree, the issue is fixed by finding the `second_largest_t` as well, and
compare that with the new insertion to find the new `max_t`.
Pull Request: https://projects.blender.org/blender/blender/pulls/125739
Weizhen Huang
d4ceade5ea