Not that either way would be more correct than the other (this is what
three.js uses I think), but it was documented everywhere to be
1/(1 + d^2)
but the calculation instead did
1/(1 + d)^2
This now also means the analytical test equation works. I should have
paid more attention to it not matching before, because that obviously
pointed to this problem.
Point lights are now significantly brighter than before, the tests were
updated to use a larger distance to avoid issues with overflows. Does
not affect the (default) directional lights in any way.
This is a -- long overdue -- breaking change to the rendering output of
this shader, finally adding support for lights that get darker over
distance. The attenuation equation is basically what's documented in
LightData, and the distinction between directional and point lights is
made using a newly added the fourth component of position (which means
the old three-component setters are all deprecated). This allows the
shader code to be practically branchless, which I find to be nice.
This breaks basically all rendering output so all existing Phong and
MeshTools::compile() test outputs had to be regenerated.
Interestingly enough / sadly none of the tests showed a clear difference
when removing the incorrect normalization, so here's a dedicated test
case. Sigh.
Vladimír Vondruš