arch-line-weights

Apply architectural line-weight hierarchy AND solid-black poché AND material-specific hatching to a Rhino-exported .ai or .pdf, in seconds, with all your original layers preserved.

If you've ever exported a section, plan, or elevation from Rhino and watched all 340,000 strokes come out at a uniform 1.0 pt — and then tried to fix it inside Illustrator only to have ExtendScript hang for hours — this is for you.

$ arch-lw apply "DRAWING 4 SECTION [Converted].ai" --auto --preset section
# 37 colors mapped using auto:section
--- 1.0 pt ---
  RGB( 40, 40, 40)    5,862 strokes
  ...
applied 340,323 strokes across 49 color changes
   0.08 pt  →  298,443 strokes
   0.18 pt  →    6,381 strokes
   0.25 pt  →      494 strokes
    0.3 pt  →   25,120 strokes
    0.5 pt  →    3,967 strokes
    1.0 pt  →    5,918 strokes

wrote DRAWING 4 SECTION [Converted] HIERARCHY.ai  (4,081,388 bytes)

Total runtime: under 2 minutes for a 24 MB / 340 K-stroke file.

Install

git clone https://github.com/zohartito/arch-line-weights
cd arch-line-weights
pip install -e .

This installs the arch-lw CLI.

To wire up the Claude Code skill:

ln -s "$(pwd)/skills/apply-arch-hierarchy" ~/.claude/skills/apply-arch-hierarchy

After the symlink, ask Claude Code to "apply line weights to my section" and the skill will fire.

Usage

Inspect first

Always look at the color distribution before applying. Most Rhino-export files have ~10–50 unique stroke colors, one per Rhino layer:

arch-lw inspect drawing.ai > inspect.json

The JSON contains every stroke RGB and how many strokes use it. The dominant colors (highest counts) are almost always material hatch / texture — they should land in the lightest tier.

Two apply modes — pick by what you need

# Layer-preserving (recommended for Rhino-export .ai files):
arch-lw apply-jsx drawing.ai

# pikepdf-fast (loses layer structure):
arch-lw apply drawing.ai --auto --preset section

apply-jsx uses a semantic layer-name classifier: anything in a Visible::ClippingPlaneIntersections::* OCG is the section cut (1.0 pt); TEC_TIMBER_*, TEC_CLT_*, TEC_FOUNDATION etc. are structure (0.5 pt); SHS_* are secondary steel (0.35 pt); WINDOW_GLASS is glazing (0.25 pt); cladding (CU_*) is material (0.18 pt); EPDM and FLOOR_DATUMS are reference (0.13 pt). See docs/POSTMORTEM.md for why this is better than color-based classification for Rhino files.

apply (pikepdf mode) buckets colors into the preset's tier ladder by luminance. Good fallback for non-Rhino files where layer names don't encode semantics.

arch-lw apply drawing.ai --auto --preset section --dry-run    # preview
arch-lw apply drawing.ai --auto --preset section              # commit

Add --dry-run to either to print the planned mapping without writing.

Apply with a hand-edited mapping

When auto-mode misclassifies (e.g., it sticks "structural framing" in the texture tier because it's the most common color), copy examples/sample-mapping.json, edit, and pass it:

arch-lw apply drawing.ai --mapping my-mapping.json

A mapping file is just {"RGB(r,g,b)": weight_pt, ...}. Any color absent from the mapping gets --default-width (0.25 pt unless overridden).

How it works (and why it's fast)

A .ai file is a PDF with extra. The PDF content stream has all the path geometry; the .ai adds an /PieceInfo /Illustrator /Private block that caches the same geometry in Adobe's native format. Illustrator reads from the private block, ignoring the PDF stream when it can.

arch-lw apply does two things:

1. Rewrites the PDF content stream: for every stroke operator (S, s, B, B*, b, b*) it injects <width> w ahead, where <width> comes from the per-color mapping. Tracks the most recent RG (set stroke RGB) to know which color the stroke is.
2. Strips /PieceInfo: so Illustrator has no choice but to re-parse the modified PDF stream. Illustrator rebuilds its private cache on first save.

This sidesteps ExtendScript entirely. Per-item iteration in ExtendScript on 340 K paths exhibits exponential slowdown from undo-history bloat — the same work in pikepdf is a single linear pass.

Tier presets (pt)

The "Special" tier is for glazing / water / sky — anything not architectural that you want held back at a mid weight regardless of darkness.

Limitations

• Only RGB stroke colors are remapped. CMYK and Gray strokes get --default-width. (Most Rhino exports are RGB.)
• The PDF stream rewrite is for stroked geometry only. Filled paths are not touched (Rhino exports rarely have fills).
• Stripping /PieceInfo means Illustrator opens the file as if it were a generic PDF — flat, single-layer. If your .ai had carefully organized layers/groups (rare for Rhino exports), --keep-pieceinfo preserves them but Illustrator will then ignore the new widths. Pick your poison.
• Multi-page documents are supported; every page gets the same treatment.

Roadmap

• Phase 1 — MVP: inspect + apply, auto-by-luminance, JSON mappings, presets
• Phase 2 — Claude Code skill: install once, invoke via slash command
• Phase 3 — Smarter classify: use saturation + hue family + frequency to detect glazing/water/structural/texture automatically
• Phase 4 — Per-drawing-type defaults; preview generator
• Phase 5 — SVG support; native PDF input alongside .ai
• Phase 6 — Batch + watch mode for live Rhino-export workflows
• Phase 7 — pip install arch-line-weights from PyPI

License

MIT.