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Geometry, Lines, Arcs, and Ridge

Status: Current geometry evidence families with comparison paths retained

Authority: Current contract; ridge accuracy targets remain unverified

Last reviewed: 2026-08-14

Question

What geometry evidence does Detection expose, and what does that evidence mean?

Short answer

Detection exposes geometry as reviewable carriers and support evidence. Line/Arc fitting, ridge centrelines, and vector-derived centrelines remain visible. Outline boundaries are not engineering lines before centreline conversion.

Line and arc fitting

Line/Arc fitting starts from ink points on a Detection input. It builds a dense raster vectorize graph without Hough. It recovers junctions, splits, and trail pieces. Support points are the ink points that still back a candidate. Carrier grouping joins collinear fragments into longer line carriers. Support bounds mark where raster support remains along each carrier. Curves that a line carrier already explains are suppressed. Remaining curves become residual curve tracks. The method is slower than Fast Dimension Lines because it builds a dense graph and refines support for every input. These primitives remain fallback and comparison evidence. They also help later local arc work for diameter, radius, and angle cases.

Ridge detection

Ridge detection finds ridge pixels along stroke ridges. Path linking joins those pixels into ridge paths and junctions. Vector carriers turn paths into open centreline polylines. Ridge evidence aims at true stroke centrelines. Optional consolidation can join paths across gaps without assigning geometry type. Ridge consolidation accuracy remains pending human benchmark. Do not treat ridge targets as validated accuracy.

Vector-derived geometry

Potrace recipe potrace-0.80 traces closed ink outlines. Those outlines are appearance evidence. Inkscape four-scan remains a sharp-dark multi-scan appearance benchmark. Vector Lines reconstructs fill from Potrace outlines. It then derives a medial-axis centreline and fits compatible Hough segments. Appearance evidence stays separate from engineering geometry. Deeper vector method detail lives in Vectorization.

Use in dimensions

Fast Dimension Lines currently uses page-wide straight-line carriers. Dimensions from Line/Arc and Dimensions from Vector Lines remain independently visible comparison methods. Do not automatically fuse geometry-source candidates.

Open Questions

  • When do type-specific local arc and circle searches join the primary Detection path?

Sources