3D effects: merged contours keep their parts, and edge cases are consistent

The boolean's answer went through orient(), which judges each ring's
side from its first point. The boolean often starts a contour where it
touches another, so a triangle whose tip rests on a square's edge was
dropped, and an even-odd hole touching its outline was filled. The
boolean already runs holes against their outlines, so its rings are now
only turned as a whole.

Other fixes:
- A bowtie drawn as one contour has no area of its own. It was dropped
  before the meet check and built nothing, although it fills both lobes.
  Sampling now keeps rings with no area, and orient() drops them after
  the check. Flat rings, every point on one line, fill nothing and are
  still dropped, so a stray flat contour doesn't send separate art
  through the boolean.
- An open subpath was closed along its end handles when the profile went
  through the boolean, but straight otherwise, as the renderer fills it.
  It is now closed straight before the boolean too.
- An empty union was taken as a refusal. Contours that cancel (a square
  drawn twice under even-odd) built a square. They now build nothing.
- Contours meet within twice the boolean's own sweep tolerance,
  computed by its rule from every anchor and handle of the path it is
  given. pathops snaps anchors onto nearby heights before the sweep
  joins edges within that tolerance, so contours up to about 1.4 times
  it apart can come out as one; within twice it, every contour it
  might join goes through it, even far from the origin, and the few it
  leaves apart cost a boolean that builds the same shape.
- A one-anchor subpath draws nothing, so it is skipped, as the renderer
  and the boolean skip it.
- A profile the boolean refuses reuses the rings already sampled.

Tests:
- touching parts and holes;
- an open subpath with handles, alone and beside crossing bars;
- a flat contour beside separate squares;
- contours joined far from the origin, including by handles alone,
  and contours a few millionths apart near it kept apart;
- triangles snapped together and joined at 1.4 times the tolerance,
  the same triangles left apart and kept whole, and the factor pinned
  between 1.9 and 2.2 times, with the worst case just past twice the
  tolerance left apart by pathops;
- a 24-bar grid: too complex for Extrude and Inflate, whole under Rotate;
- the merged rings turned as a whole;
- a one-anchor loop;
- the bowtie and the cancelling squares under all three effects;
- a 3,001-point star that the boolean refuses (TooComplex), built as
  drawn.

Docs: the pathops README's Limits section now says only the try_
functions refuse, lists OpenPath and the caught panic, and describes
unite_all's answers, and which calls take a precision. three-d.md and effects-parity.md (the 3D row, its
history and status line) describe the merge and its limits.

docs/effects-parity.md

@@ -1,6 +1,6 @@
 # Effects parity
 
-> **Last reviewed:** 2026-10-10 · **Last updated:** 2026-11-06 · **Change:** minor (Extrude & Bevel, Inflate and Rotate apply to groups and layers, their objects turning about one shared axis (#4506); the Transform effect's copies of a path with a fill and a stroke (or several fills and strokes, an even-odd fill, or a partly transparent one) are drawn each above the one before, as Expand Appearance makes them (#5920); Expand Appearance makes each copy of a path's Transform effect an object of its own (#5612); previously: Pixelate › Color Halftone: Max Radius in pixels of the Document Raster Effects resolution, 4–127 px, with older documents converted on opening and radii written back in points for older app versions (#3260); Effect dialogs clamp bounded length inputs immediately on commit and flash rejection on invalid input (#4638); previously: Drop Shadow Darkness uses fixed RGB subtraction and CMYK black addition; scores unchanged; Pathfinder › Trap: the Pathfinder panel's Trap… and Effect › Pathfinder › Trap… add an overprinting strip of the lighter colour where two solid colours meet; recounted with Hard Mix (#3061) and Soft Mix already in the catalogue: Pathfinder 13/13, Illustrator effects 49/50) · **Target:** Adobe Illustrator 2026 (30.x)
+> **Last reviewed:** 2026-10-10 · **Last updated:** 2026-11-08 · **Change:** minor (Extrude & Bevel, Inflate and Rotate merge contours that cross, touch or overlap, as type often draws a glyph, before building a solid; previously: Extrude & Bevel, Inflate and Rotate apply to groups and layers, their objects turning about one shared axis (#4506); the Transform effect's copies of a path with a fill and a stroke (or several fills and strokes, an even-odd fill, or a partly transparent one) are drawn each above the one before, as Expand Appearance makes them (#5920); Expand Appearance makes each copy of a path's Transform effect an object of its own (#5612); previously: Pixelate › Color Halftone: Max Radius in pixels of the Document Raster Effects resolution, 4–127 px, with older documents converted on opening and radii written back in points for older app versions (#3260); Effect dialogs clamp bounded length inputs immediately on commit and flash rejection on invalid input (#4638); previously: Drop Shadow Darkness uses fixed RGB subtraction and CMYK black addition; scores unchanged; Pathfinder › Trap: the Pathfinder panel's Trap… and Effect › Pathfinder › Trap… add an overprinting strip of the lighter colour where two solid colours meet; recounted with Hard Mix (#3061) and Soft Mix already in the catalogue: Pathfinder 13/13, Illustrator effects 49/50) · **Target:** Adobe Illustrator 2026 (30.x)
 
 Every entry of Illustrator's Effect menu, by its public feature name, against VectorCraft's effects catalogue
 (`effect_catalog()` in `crates/effects/src/lib.rs`) and the Effect menu built from it
@@ -179,7 +179,7 @@ VectorCraft choices; an original approximation, never compared with another appl
 | Item | Ours |
 |---|---|
 | Revolve | initial: live, editable profile, rotation and light gizmos, default-on Cap with continuous curved rims, smooth vector shading and round seam joins, SVG/PDF output, Expand Appearance ([revolve.md](revolve.md), #846) |
-| Extrude & Bevel, Inflate, Rotate | initial: live, depth, twist, taper, solid or hollow caps, five original bevel shapes, Inflate volume, both sides, twist, taper and cap, Rotate of every fill and stroke, groups and layers turned about one shared axis (#4506), Position presets, rotation and light gizmos, SVG/PDF output, Expand Appearance ([three-d.md](three-d.md)) |
+| Extrude & Bevel, Inflate, Rotate | initial: live, depth, twist, taper, solid or hollow caps, five original bevel shapes, Inflate volume, both sides, twist, taper and cap, Rotate of every fill and stroke, groups and layers turned about one shared axis (#4506), contours that cross, touch or overlap merged first ([three-d.md](three-d.md)), Position presets, rotation and light gizmos, SVG/PDF output, Expand Appearance ([three-d.md](three-d.md)) |
 | Materials panel, lighting, ray-traced render | Window › 3D and Materials panel with the object types (Plane, Extrude, Revolve, Inflate) and the Object, Rotation and Lighting settings of the applied effect ([three-d.md](three-d.md#3d-and-materials-panel)); one to ten directional lights with per-light Color (opaque RGB, white by default), Intensity, Rotation, Height, Softness and neutral Ambient Light, Revolve and colored Inflate use smooth vector shading; Extrude & Bevel and Rotate retain planar shading; original Standard, Diffuse, Top Left and Right lighting rigs; no materials, shadows or ray tracing |
 | 3D (Classic): Extrude & Bevel, Revolve, Rotate | none |
 | Turntable (30.0 beta) | none |
@@ -193,6 +193,7 @@ angular cut caps, exact visibility, 3D Classic, Turntable) is 25–45 h.
 
 | Date | Change | Summary |
 |---|---|---|
+| 2026-11-08 | minor | Extrude & Bevel, Inflate and Rotate merge contours that cross, touch or overlap (a glyph's arm across its stem) before building a solid, so the solid follows the shape as it is filled; others are built as drawn ([three-d.md](three-d.md)); scores and estimates unchanged |
 | 2026-11-06 | minor | Extrude & Bevel, Inflate and Rotate apply to a group or layer: a solid for every path, compound path and type in it, all turned about one shared axis as the public documentation describes for groups ([three-d.md](three-d.md#groups), #4506); scores and estimates unchanged |
 | 2026-11-06 | minor | The Transform effect's copies of a path or compound path whose fills and strokes stack (a fill and a stroke, several of either, an even-odd fill, or a partly transparent or blended one) are drawn each as an object of its own above the one before, as Expand Appearance makes them, instead of one path of every copy whose fill lay under every copy's stroke (#5920). A single opaque stroke or nonzero fill still draws as one path. Counts unchanged. |
 | 2026-11-04 | minor | Expand Appearance of a path or compound path whose Transform effect makes copies gives a group of one object per copy, each with the path's fills and strokes, instead of one compound path of every copy; copies of copies nest (#5612). Counts unchanged. |

docs/three-d.md

@@ -19,8 +19,11 @@ another.
 
 Each solid follows its shape as it is filled. Separate and nested contours are built as drawn. Contours that cross,
 touch or run along each other or themselves, as type often draws a glyph, are first merged into one outline by
-[`vectorcraft-pathops`](../crates/pathops/README.md), keeping contours however narrow. All three effects then share
-its [limits](../crates/pathops/README.md#limits): a shape it refuses is built from its contours as drawn, where it can be.
+[`vectorcraft-pathops`](../crates/pathops/README.md), keeping every contour but the numerical debris a boolean leaves.
+Whether contours meet is judged on the outline as it is followed (see the curve tolerance below), so curves that
+overlap by less than that are built as drawn. All three effects share pathops'
+[limits](../crates/pathops/README.md#limits): a shape it refuses is built from its contours as drawn, where it can be.
+An open subpath is closed by a straight line either way.
 
 ## 3D and Materials panel
 
@@ -234,8 +237,8 @@ out, perspective). No Adobe software, assets, presets or bevel shapes were used.
 - Curves are followed within 1/2000 of the shape's size (at least 0.05 pt), so a small curve takes a few points
   and a large one up to 32. Extrude & Bevel and Inflate take up to 2,048 outline points (a stroke's outline is
   counted on its own), Rotate (which only turns the outline) 65,536. The limit is counted on the shape as drawn and,
-  when its contours meet, again on the merged outline, which can have more points: bars crossing in a grid trace
-  every hole between them.
+  when its contours meet, again on the merged outline, which can have more points (bars crossing in a grid trace
+  every hole between them); past it, the shape is too complex for the effect.
 - **3D (Classic)** (the track cube, surface types, blend steps, map art), Turntable and 3D export are separate,
   unbuilt items.