A rung used to fix the gridunit SPACING, with the canvas extent falling out
of spacing x cell count. That is why the top of the ladder was unusable: at
REGION_M spacing a viewport-sized canvas spanned ~251,658 km — six times
around a rocky body — so the Region rung capped to the body and redrew the
Global picture pixel-for-pixel. "Global and region look the same" was not a
rendering bug; it was this relation, stated in metres.
Inverted: a rung fixes the EXTENT and the spacing falls out of the canvas
size. The shorter viewport axis spans exactly one cell of the rung's level,
so a widescreen window shows more ground on the long axis rather than less
on the short one. Every rung now shows the ground its name promises —
Region 262x466 km, District 4.1x7.3 km — and the canvas cell count is
viewport-driven and identical at every rung, so derive cost no longer varies
with depth and resize is free.
Consequences that fell out of the inversion rather than being chosen:
- Region leaves the orbital derive set. It was envelope-only because at
251,658 km nothing finer made sense; at 262 km it is a genuine provincial
map and takes the full courses-aware derive. Region having no rivers at
all was much of why the top of the ladder read flat. It also joins the
deep display ratio for the same reason.
- The S2 station-spacing floor is deleted, not retuned. It guarded an
O(1/spacing) blowup that the inversion makes structurally impossible (the
canvas cell count is now constant across rungs, so stations-per-course is
bounded however deep you scroll). Kept, it would do active harm in the
opposite direction: a 2,048 m pitch across a 3.6 km District canvas places
two stations and draws every river as a straight line. Station placement
gets its own generator pass.
- cap_extent_to_body is superseded and now a documented no-op. A canvas can
no longer over-request a body by construction. The residual question —
whether a rung's cell exceeds the whole body — is liveness, not capping,
and is_rung_live_on_body() answers it by omitting the rung. Empirically it
never fires on inhabited content: all six rungs are live on all 271
populated bodies with a radius.
- snap_to_gridunit no longer truncates its multiplier to int. Post-inversion
the deep rungs run sub-metre (Chunk ~0.12 m at a 1080 px short axis), where
int(spacing) floors to zero and would collapse every request centre onto
the origin.
Both sides derive spacing from the same three inputs (rung, echoed cell
extent, body radius) rather than one telling the other, so there is nothing
to keep in sync beyond the constant table itself. Body radius already
reaches the viewer via enter(); no wire change.
Pair session with Jeroen, 2026-07-26. D-243/D-255 amendments to be backfiled.
Co-Authored-By: Claude <noreply@anthropic.com>
jpmschweitzerandClaude
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