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Line/Arc and Vector-Line Comparisons

Status: Independently visible comparison methods retained

Authority: Current contract (2026-08-12)

Last reviewed: 2026-08-14

Question

Why does Drawing Lab keep Line/Arc and Vector Lines beside Fast Dimension Lines?

Short answer

Comparison methods stay independently reviewable. No geometry source is automatically fused. Line/Arc remains fallback evidence. Vector Lines recovers centrelines from Potrace-derived outlines. Fast Dimension Lines is the current fast Detection path.

Dimensions from Line/Arc

This path uses fitted line and arc primitives. It starts from ink points and groups carriers with support bounds. Residual curves remain after line carriers explain what they can. The denser fitting work is slower than the page-wide Fast Dimension Lines Hough pass. It remains useful when comparing carriers and later local arc needs.

Dimensions from Vector Lines

This path uses Potrace recipe potrace-0.80 appearance output. It reconstructs fill from closed outlines. It derives a medial-axis centreline from that fill. It then fits compatible Hough segments for dimension comparison. Outline boundaries are not engineering lines before that conversion. See Outline Versus Centreline.

Stage ownership

All three methods can contribute Detection evidence. Understand still owns type, units, view ownership, and measured-feature ownership. Do not treat any comparison overlay as confirmed dimensions.

Local arc policy

Local arc and circle fitting remains a later bounded supplement. Use it for diameter, radius, and angular cases when a possible dimension needs that geometry. Do not hide that step inside a fused detector claim.

Open Questions

  • After representative review, does one comparison geometry source become the default fallback?

Sources