The optics the predicate is a statement about.
A node refines while distance < spacing · scale and scale goes as
pixelsPerRadian, so doubling it is one more level of refinement everywhere
on the visible disk. The focal-length control spans 8.1× of it — 378 px/rad
at 110° to 3,062 at 20° — which is three levels, and the zoom channel
multiplies another 8× for six levels across the two sliders together. The
patches do not follow the square of it: refinement runs out of levels at
surfaceDetailFloor before it runs out of budget, so 20° at zoom 1 measures
1.9× to 3.2× the demand rather than the 66× the arithmetic suggests —
DEFAULT_MAX_PATCHES below carries the counts, including the corner where
the floor is reached and the square starts to bite again. That is why the
predicate takes the lens the picture is actually composed through rather than
a nominal angle: a fixed one is right for exactly one setting of the two
controls and wrong by six levels at their ends.
LENS_PRESETS.flight over BASELINE_VIEWPORT — 65° over 1080 display
pixels, which is 848 px/rad. The streamer passes the live lens; this is what
the headless probe and the tests measure against, and naming it here is what
keeps those numbers comparable between runs.