MLINE dashed elements were fully CPU-expanded (apply_along) — one wire per
dash — to keep the parallel lines in phase. Move pure-dash elements onto the
GPU dash shader and end-align every element to the multiline's centre-line so
they share one interior phase.
- wire_distances now accumulates arc-length from the double-single (high+low)
points, so the dash phase stays precise at UTM coordinates. f32-high-only
deltas quantised ~0.1 there and drifted the parallel lines apart — the
original reason MLINE dashes were CPU-side.
- New WireModel.dash_align_end carries a shared begin/end dash length. The
shader uses it as align_end for every parallel element (the interior phase
depends on align_end, not the wire's own length) while align_total stays the
element's own length, so each still ends on a dash at its own endpoint.
- MLINE tessellation derives that length once from the centre-line, routes
pure dash/space/dot elements to the GPU pattern and text-bearing elements to
apply_along.
- apply_along gained an "A"-type mode (shared reference length): a solid
begin/end dash and a phased interior, so its dashes — and embedded text —
line up with the GPU-dashed sibling elements instead of tiling from start.
Pure-dash MLINEs now cost one WireModel + pattern per element instead of N
segments; single (non-MLINE) entities keep the from-start tiling unchanged.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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