This was caught by ASAN.
Our algorithm header has many one-liners that compute the "next power of
two length / 2" but they all have the caveat that if the input is
already POT, then the "/ 2" part does not occur.
Usually we deal with this by testing the difference against zero.
However in `partition_point` we were skipping the test, thus causing a
potential out-of-bounds access.
I fixed `partition_point` and added a few more tests for non-POT cases.
the C++ standard says:
if T is a class type with a default constructor that is neither
user-provided nor deleted (that is, it may be a class with an
implicitly-defined or defaulted default constructor), the object
is zero-initialized and then it is default-initialized if it has a
non-trivial default constructor
Unfortunately, MSVC always calls the default constructor, even if it
is trivial, which breaks constexpr-ness.
To workaround this, we're always zero-initializing TVecN<>
Also removed constexpr from default constructors, since they never can
be constexpr as they're not initializing the vector.
computeLightTree() takes a list of light as
a bitfield and produces a depth-first
binary tree array that can be used to efficiently
check which lights volumes contain a given z
coordinate in screen space.
Currently computeLightTree() produces the array
locally on the stack, which isn’t useful, but
before we can make use of it, a lot of other
things have to happen.
