Oculus - Au Naturel Edit

Oculus Au Naturel — latitude/season-aware shadows
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Shadows and light rays now follow the sun and moon to the positions the
shader actually draws them at, instead of the positions they would occupy
with no latitude or seasonal adjustment.

Previously the shader tilted the sun's path for latitude and time of year,
which moved the visible sun, moon, sky, clouds and volumetrics — but could
not move the shadow map, because that is rasterised by the engine from the
celestial angle and no fragment shader can reach it. Cast shadows therefore
disagreed with the visible sun by the whole adjustment: roughly 10-12
degrees a couple of thousand blocks from the equator, and up to ~68 degrees
at high latitude in midwinter.

The tilt is now computed engine-side and folded into sunPathRotation for
the shadow path only:

  - the shadow map render
  - the shadowModelView uniform
  - the shadow culling frustum

The visual path of the rendered sun and moon are deliberately untouched. The sun, moon texture and moon glow keep their existing shader-side adjustment, which already worked.

Because the volumetric light shafts are carved by shadow-map sampling
rather than drawn along the light vector, the god rays above water and the
shafts below it follow the corrected shadow map automatically. Voxy's
heightmap terrain shadows were already baked with the adjusted direction,
so near and distant shadows now agree with each other for the first time.

Other packs are unaffected: the adjustment is zero unless the loaded pack
declares LATITUDE_SUN_PATH_INTENSITY, and that option remains a slider on
the pack's own options screen.

The tilt angle is quantised to 0.1 degrees. The shadow projection is
snapped to a world grid to keep shadow texels stable as the player moves;