lighting demo

Signed in as __USERNAME__. The volumetric media lighting experiment, forked from the sandbox: the bridge scene at 512×448 hi-res on a 12Hz render cadence (60Hz sim, the present pan covering camera movement between redraws). On top of the shared renderer: a world-aligned 3D density volume (smog/fog/mist/spray/smoke, per-type base colors averaged per voxel) and a scattering volume lit by every light through the surface pass's own volumetric shadow march, composited by a Beer-Lambert view-ray march. M A/Bs against the legacy analytic weather march. Other controls as in the sandbox: QWE/AD/ZSC or the left stick walk the 8 compass directions; Numpad +/− adjusts speed; the right stick or arrow keys override facing; [/] or D-pad cycles the character; the mouse wheel steps integer zoom, R resets; N toggles day/night, T the torch, U the tuning panel.