meshLod.module

Owns which level each tracked entity draws at, and the arithmetic that decides it.

screenFraction(radius, distance, fovDegrees) returns the fraction of the viewport's height a sphere of that radius spans — 1.0 fills the frame, 0.05 spans a twentieth of it.

selectLevel(fraction, thresholds, current, hysteresis) maps that fraction to a level. thresholds are ordered largest to smallest, one per cheaper level; level 0 is the authored full-detail mesh. Passing current lets the climb back to a richer level require 1 + hysteresis times the threshold that was crossed, so a camera resting on a boundary settles instead of alternating.

Both are pure, so a level can be checked for a given size and range without a camera or a scene.

register / unregister track an entity, evaluate measures one against the camera and returns the level, the mesh to draw and whether that changed. The caller applies the mesh — the module never writes another component's fields.

levelOf, fractionOf and stats report what is being drawn and the measurement it came from.