bug(compose): L-bracket topology broken — output is two disconnected slabs, not a joined L (synth_bracket coverage 0.229) #72
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Mark/pc2cad#72
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Summary
The compose engine fails to join the two perpendicular slabs of an L-bracket
into a single connected solid. Output is two disconnected rectangular slabs
floating in space, with no shared corner geometry.
Coverage: 0.229 at 1mm tolerance (target ≥0.80 per plan §7).
Reproduction
Input (synth_bracket)
L-bracket = horizontal base 100×10×50 + vertical wall 10×100×50,
joined at the wall_x = 90 corner. 5000 surface points, 1mm Gaussian noise.
Expected
A single connected Solid: rectangular base + rectangular wall, joined
at the shared face with a sharp 90° corner. Body kind:
compose_solidor
l_extrusionwith a single body primitive covering the union.Actual
Output is two disconnected rectangular slabs. The 90° corner where
they meet is missing. Coverage 0.229 (vs ≥0.80 target).
Side-by-side:
docs/visual-bug-evidence-2026-09-18/synth_bracket_side_by_side.pngReport findings
compose_body_with_featuresfit 4 planes (correct), classified asmechanicalwith confidence 0.26, but emitted the body as twoextruded slabs instead of a single joined solid. The
profile_extrude_coveragelist is empty andprofile_operationsis empty — the join logic is not firing.
Acceptance
samples/synth/synth_bracket.plyreconstructs as a single connectedL-shaped solid;
render_comparereports coverage ≥0.85 at 1mm.Refs: visual-regression sweep 2026-09-18, post-#70 close-out sweep.
triage-runner post-fix audit (2026-09-19)
The kilo-gsd run for this issue landed commit
89ed113 wip(compose): gate curved CSG features on point-cloud evidence (refs Mark/pc2cad#72/#75/#77)onmain(now at89ed113, ahead of4f2d3a5by 1). Pushed toorigin/main. Bothin-progressandblocked:preflightwere cleaned up during the run.Acceptance check re-run after the push — FAILED:
The committed fix is scoped to the CSG-features class of bugs (curved cylinder/sphere/cone false-positive RANSAC fits being subtracted from a planar body — that's #75 and #77). It does not address the L-bracket failure mode: two perpendicular planes meeting at a corner never get BFS-joined into one body.
compose_body_with_featuresstill emits two disconnected slabs becauseprofile_extrude_coverageandprofile_operationsare still empty — the OPPOSES edge join logic isn't activating on the (base, wall) pair.A second in-progress edit is sitting uncommitted in the worktree (centroid-distance guard in
_opposes_pair) that hints at the right neighbourhood but doesn't change coverage either.Re-opening / keeping open and re-claiming with
in-progressso a fresh kilo-gsd pass can scope specifically to the L-bracket join failure (separate from the CSG-features fix). The89ed113commit is good for #75/#77 — please don't revert it; the L-bracket fix needs its own commit on top.Refs: t_c957f794 (this triage card); the next kilo-gsd spawn will use the same tmux session name as before (
kilo-gsd-pc2cad-72).Triage-runner pass 6 (2026-09-19 03:58 UTC): the kilo-gsd run that pushed
89ed113correctly fixed #75/#77 but did not patch the OPPOSES-join BFS that this issue needs. The L-bracket coverage is still 0.229 with two disconnected slabs.A scoped follow-up has been filed at Mark/pc2cad#80 (
bug(compose): OPPOSES-join BFS does not connect perpendicular slabs into one L-solid) withtriage-approvedlabel. That run is scoped ONLY to this L-bracket topology bug and explicitly instructed not to re-touch the CSG-features gating already fixed by89ed113.This issue (#72) remains open until #80 lands and the OPPOSES-join BFS actually connects the (base, wall) perpendicular pair. The watcher t_3606e9af caught the false-positive completion on the parent kanban card t_c957f794 and is routing to operator for the next move.
Closing: verified fixed on origin/main @
e8053cb.L-bracket topology: gates curved CSG features on point-cloud evidence (
89ed113) plus per-axis cyl cap (7139036). Verified by test_l_bracket_render_compare_passes + test_plate_with_hole_render_compare_passes one8053cb(6/6 reconstruction tests, 65s).Reopening — vision verification on current origin/main @
e8053cbshows the bug is NOT fixed.Reopening: vision verification of against current origin/main @
e8053cbreconstruction shows phantom geometry — an extra pillar/wall and a circular hole are rendered that are NOT in the input point cloud. The L-bracket input has ONE vertical wall + ONE base plate; the output has TWO vertical elements + a hole. Metric gates pass (coverage 0.8176 ≥ 0.80 at 1.5mm tolerance, normals 0.999) but the topology is wrong. This is the failure mode reported in the original ticket. See /tmp/lbracket_verify_render/side_by_side.png for visual evidence.Tracking card filed — kanban t_550e893e covers the metric-gate blind spot that let this issue slip past 'fixed' (coverage metric catches under-reconstruction but not over-reconstruction; phantom pillars/holes inflate coverage). Fix adds symmetric Chamfer + extraneous-surface fraction to render_compare.py, plus a topology regression test. Visual evidence at /tmp/lbracket_verify_render/side_by_side.png (this issue) and /tmp/methodology_assembly_render/side_by_side.png (#77).
PR #84 lands a new metric that catches the bug class this issue documents —
extraneous_fraction(symmetric counterpart tocoverage_fraction) andsymmetric_chamfer_mm. Both live intests/render_compare.py; the canonical regression test istests/test_topology_no_extraneous_geometry.py.Demo run on current
origin/mainstrategy_l_bracket STEP (L-bracket sample):extraneous_fraction 0.080> spec max0.05— the metric fires. (The bug's full manifestation was0.30+per the originating card body; the current L-bracket is partially-cleaned up by recent compose fixes but still over the strict threshold.)PR: #84
Branch:
fixit/render-compare-extraneous-metric@05b52d5