Two faults, both reported from looking at the model.
The sails passed through the buck. A tilted shaft spreads its sails through
depth -- at 0.14 rad a 3.5 m sail swings 0.49 m fore and aft -- and with the
hub only 0.08 m in front of the gable the whole lower half of the disc was
inside the building. Both halves of the fix are what a real mill does: the
shaft tilts a few degrees rather than eight, just enough to keep the sails
off the boarding and put some of their weight on the thrust bearing, and it
projects far enough out that the sweep happens clear of the wall. Far
enough and no further -- the clearance the disc needs is sailLength times
sin(tilt), about 0.26 m, and the first correction overshot to nearly a
metre, which left the sails hanging off the gable with only the shaft
between them.
And the tail ladder climbed to blank boarding. A mill is entered from its
tail, through the one wall the sails never sweep past, and the miller comes
up the same ladder he turns the mill with; a flight of steps ending at a
plain wall was the one thing about this model that could not be true. The
door is boarded proud of the wall with two ledges and a frame, because
there are no booleans in this geometry and a door of applied planks is how
a plank building is actually closed.
28 models, 20 679 triangles, all checks pass, 0 floating cases, build clean.
Opening the viewer showed the mill reporting one material while declaring
two. It declared an `iron` slot and used it nowhere: the windshaft's own
comment called it iron-banded and then painted it oak like everything else.
Four sails pull on one shaft from four directions and what holds the whips
to it is iron strapping, so the bands are real and now exist.
Adding them exposed something that had been wrong since the model was
written. `taperedBoxGeometry` takes its third argument as a Y height, so
the shaft -- written with no rotation and only a z offset -- was a short
vertical post standing inside the buck rather than a shaft projecting from
the front gable. Buried in the body it survived every render unseen. The
bands, built the same way, came out coaxial with it, and the z-fight check
reported that immediately.
Two smaller things settled on the way.
The bands first went into `trestle`, where the support check found them
hanging at the model's origin: they are authored around the hub, so they
only make sense in the frame of the part whose origin is the hub. They
belong to `sails` anyway, since the shaft turns with them -- in a real mill
the sails are keyed to it.
And the four sails converged on the hub in perfect symmetry with their
faces meeting there. The fix is how the sails are actually carried: TWO
stocks pass through the shaft at right angles, one behind the other, each
carrying a sail at both ends. Four timbers cannot occupy one crossing, and
the check was right to say so.
Worth recording how the shaft was found, because reasoning about it failed
three times. Rebuilding the four sails alone, in every combination of whip,
rail and bars, gave zero overlaps -- which ruled the sails out and left only
what else was in that part.
28 models, 20 547 triangles, all checks pass, 0 floating cases, GLB
round-trip clean, Conformant, build clean.
The largest thing in the kit, and the one whose name is its whole design:
the entire body -- millstones, gearing, miller and all -- is balanced on one
massive vertical post and turns bodily on it, so the sails can be pointed
into whatever wind there is. The miller does that by walking the tail
ladder round, which is why the ladder is not a way up but a lever, and why
it reaches so far behind the mill.
Four parts, in the order the thing is built: `trestle` (two cross-trees,
the post standing on them, four quarter-bars), `body` (the boarded buck and
its pitched roof), `sails` (a windshaft leaving the front gable, with its
own origin so `setTurning` spins it alone), and `ladder`. `setTurning`,
`setAngle` and `update` drive the sails at about ten revolutions a minute
-- a working mill turns slowly, not in the blur people draw.
The sails are where the triangles went, and deliberately. A sail is not a
blade, it is a LATTICE the miller dresses with canvas according to the
wind. Drawn solid the silhouette is wrong in the one place everyone looks,
so the bars are modelled and the budget is taken from the buck's boarding,
which reads perfectly well as vertex colour. 1 516 triangles.
Four faults on the way in, all found by measuring rather than by looking:
The roof pitches were built `slope * 2` long and tilted by the complement
of the roof angle, which made two panels 2.79 m across a building 1.80 m
wide, standing up like the covers of an open book. Each pitch covers half a
roof, and the tilt is measured from the horizontal because
`chamferedBoxGeometry` takes an X-Z footprint.
The rails of the tail ladder were tilted the wrong way round. `run` is
positive -- the head sits at a larger z than the foot -- so rotating by
`-lean` laid the rails along the opposite diagonal to the one the rungs
were placed on. They crossed near the middle and diverged towards the ends,
and the bounding box looked correct the whole time because the translation
put the ladder where it belonged and only its internals were wrong. The
support audit found it as loose rungs, and found it only at the small end
of the height slider, where the voxel grid is fine enough not to bridge the
gap: the joint was never real at any size.
Fixing the ladder's foot, which sat 0.10 m below the cross-trees so the
mill hovered above whatever it was placed on, then displaced the rails
perpendicular to their own axis by almost exactly a rung's half-depth --
correcting the rails alone was worse than not correcting at all. Rails and
rungs now share one lift.
And the lowest sail tip came within 0.27 m of the ground, which reads as a
mill about to plough its own field.
28 models, 20 523 triangles, all checks pass, 0 floating cases, GLB
round-trip clean, Conformant at 30 items, build clean.
