The spec review found two places where the marker and threshold
contract does not hold.
A clamp narrower than the chord tolerance is still judged
tolerance-free against finely re-read material and reported as the
whole clamp rectangle. That existing safety policy is kept, so its
marker is the clamp's centre: within half the clamp's size (under
0.0005) of the material, though not necessarily on it. Document this
on PlateOverlapPair.Marker and in the overlap docs, and lock it in the
tiny-clamp region test.
Also document that 1e-8 grid rounding can move an area within
rounding error of the 1e-5 threshold to either side of it.
The overlap crosshair sat on the pair's area centroid. For a split,
holed or concave overlap, that point can be off the red material:
between two patches, in a hole, or inside a curve.
PlateOverlapPair.Marker is a point inside the pair's largest island.
It is the island's pole of inaccessibility (PolyLabel), searched to a
tenth of the island's area/perimeter within a 4096-cell budget. If
that bounded search does not land inside (a long thin sliver), the
marker falls back to the midpoint of the widest interior run of a
horizontal scan line placed between vertex heights.
The overlay crosshair, marker hit testing, hover coordinates
("Marker:") and the cutting-inspection ring now use the marker.
Centroid stays the true area centroid. View > Overlap Check > Display
> Centroids is now labelled Markers.
Before the marker existed, its call sites used the centroid. Two
patches, a covered frame, a half annulus and a thin crescent then put
it off the material; now all four land on it. Disabling the scan-line
fallback fails its test. On the 389-plate corpus, markers add about
0.4 ms per overlapping pair; pair and area results are unchanged.
The material-overlap diagnostic clipped every triangle of one part
against every triangle of the other, then carved each fragment by
every hole triangle. Curved overlaps produced thousands of fragments,
and a part sitting inside another part's cutout was slow even when
clear.
PlateOverlapAnalyzer now intersects each candidate pair's hole-aware
material once with Clipper2, in part-local coordinates on a 1e-8 grid.
Each operand is its outline minus the union of its holes (positive
fill rule). Regions become connected islands: a counterclockwise
outline plus clockwise Holes, including an island that both parts'
holes enclose together. PolygonAreaMoments.TrySubtract gives each
island's net moments. A pair is reported when its total shared area
exceeds Tolerance.Epsilon. Out-of-range or nonfinite coordinates make
the pair incomplete rather than clear. The overlay and the cutting
inspection highlight fill outlines with their holes.
On 389 real PEP-converted plates the pair, clamp-finding and issue
sets are identical to the previous kernel. Pair areas are equal or up
to 0.0002 larger: the kernel drops fragments below its area threshold.
With material prepared, the per-plate clipping maximum fell from
2.6 s to 52 ms (total 5.0 s to 0.5 s).
Engine and validation checks still use Collision.
PlateOverlapAnalyzer.Capture(parts, OverlapMaterialCache) reuses each clean
program's converted entities and prepared material across requests, and
Analyze(snapshot, previous) reuses pair results whose two parts kept the
same source, exact pose and relative order, renumbering them. A recheck
after moving one part only clips that part's neighbors again.
On 501 real PEP plates: full check median 1 ms / max 6.4 s; incremental
recheck after one move median 0.1 ms / max 38 ms. Incremental results
matched uncached full analysis exactly across 2505 edits.
aj