The sign read as broken, and the reason was the same one the tankard's
handle had: `bendGeometry` applied to a `boxGeometry`. A box has two levels
in Y, and two levels cannot bend -- they shear. Both the brace and the
curl were sheared parallelograms rather than curves, and the sheared curl
is what pushed the bracket's top to 0.579 while the post it is bolted to
ends at 0.442. An arm standing above its own post is not ironwork, it is a
mistake, and it had been in every render of this model. Both are now real
sweeps from `arcBarGeometry`, with their ends placed inside the post and
inside the arm rather than corrected towards them afterwards.
Replacing the curl immediately exposed a second fault that it had been
hiding. The board's part origin sat at [0, pivotY, 0] -- the post's centre
line -- while every piece of the board and its chains is authored hanging
from the cross-bar at z = reach * 0.86, half a metre away. At rest that is
invisible. The moment the swing action runs, the assembly turns about a
point it does not hang from and the tops of the chains sweep off the bar
they are looped through. The support audit had been reporting this as a
detached board only because the sheared curl was accidentally filling the
gap; with the curl the right size, it failed honestly. The origin is now
the cross-bar and the geometry is written relative to it: same place in the
world, correct axis to turn about.
Two proportions with it. The post was 62 mm square carrying a 0.72 m board
two metres up -- thinner than the board is thick, and part of a habit of
under-sizing timber that the bench, the table and the fence share. And the
chain drop was 0.12, so the five links that connect board to bracket were a
smudge; the chain is half of what makes a hanging sign read as hanging.
Lengthening the drop grew the links from radius 0.0195 to 0.0434, at which
point they interlock in earnest and their six-sided facets, all built at
the same phase, met coplanar. Each link is now indexed differently about
its own axis -- deterministically, so the seeded stream is untouched, and
a real chain does not index its links either.
27 models, 18369 triangles, all checks pass, 0 floating cases, build clean.
CRT
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