Moving the negation into the calculation of the sun angle prevents -0
getting into the vector (not that it makes much difference other than
minor confusion when reading the light data).
Maps specify sunlight as shining in a specific direction, but the
lighting system wants the direction to the sun as it's used directly in
shading calculations. Direction correctness confirmed by disabling other
lights and checking marcher's outside scene (ensuring the flat ground
was lit). As a bonus, I've finally confirmed I actually have the skybox
in the correct orientation (sunlight vector more or less matched the
position of the sun in marcher's sky).
Abyss of Pandemonium uses global ambient light a lot, but doesn't
specify it in every map (nothing extracting entities and adding a
reasonable value can't fix). I imagine some further tweaking will be
needed.
The parsing of light data from maps is now in the client library, and
basic light management is in scene. Putting the light loading code into
the Vulkan renderer was a mistake I've wanted to correct for a while.
The client code still needs a bit of cleanup, but the basics are working
nicely.
