Flags array seems uninitialized in bottom up algorithm. about bvh HOT 3 CLOSED

See the documentation for std::make_unique.
Here's the relevant quote:
[std::make_unique] Constructs an array of the given dynamic size. The array elements are value-initialized. ...
As a reminder, value-initialization for int means zeroing.

from bvh.

Ah ok that makes sense, thanks. I was assuming (mistakenly) that you are using unique_ptr's to avoid value initializing the array. So the reason to use a unique_ptr instead of a std::vector is to communicate that the arrays dont change in length?

from bvh.

First of all, as you noticed, the arrays don't change in length, so there's no need to carry around a capacity field. Second, the size field of std::vector would also be redundant here: Those arrays have the same size as the number of nodes in the BVH.
To sum things up, this at the same time conveys the idea that the size does not change, and as an additional bonus makes the generated machine code a bit simpler and the class that contains those arrays thinner (not that this is a particular bottleneck, but still, it's a nice thing to have).

from bvh.