Bathymetry Hamonshū generation implementation notes

Documentation index · Generation guide · Generation methods · Bathymetry Roulette · Natural Earth data

Outcome

bathymetry-hamonshu is a separate standard art-generation pass. It does not replace or alias bathymetry-roulette. Both use the same twelve nested Natural Earth depth thresholds, explicit overlapping projected-page cells, 24 jittered Voronoi regions, original bathymetry blue ramp, 30% graphic opacity, shallow-to-deep paint order, and six production projections. The form engine is different: this pass calls Izzi’s a60-svg-curves-hamonshu.h instead of a60-svg-curves-roulette.h.

Izzi supplies a source-indexed 153-entry procedural catalogue derived from Mori Yūzan’s 1903 Hamonshū, volume 2. Cartofreako owns the depth mapping, field layout, geographic clipping, color, metadata, layer assembly, and artifacts. The Smithsonian Libraries digitization is CC0; Natural Earth is public domain. Izzi’s descriptive English motif names identify visual forms and are not translations of historical captions.

Depth encoding

Hamonshū paths are line constructions, so this pass does not invent a roulette d/r equivalent or fill open polylines into arbitrary polygons. Instead, depth strictly increases two native Izzi parameters: line/constituent density and curvature. Independently of those art experiments, the pass restores the same shallow-to-deep blue-hue variation as the original Natural Earth bathymetry scheme. Color is therefore a redundant third cue. Every line uses its depth band’s blue at 30% opacity.

All values stay inside Izzi’s validated density range 0.25–4.0 and curvature range 0.20–4.0. Each constituent curve uses 24 relative samples. The values are categorical rendering parameters attached to Natural Earth thresholds; they are not physical models of wave energy, pressure, or current speed.

Source motifs and variation

Twelve entries from Izzi’s curated explorer provide the spatial vocabulary:

The decorative page-51 endpaper in Izzi’s thirteen-row curated explorer is intentionally excluded. Every retained entry directly describes water, current, crest, ripple, trough, channel, or spray.

The layout uses the same 1.10-unit cells and 2.15-unit base diameter as the revised roulette pass. Motif boxes vary from 0.74 to 1.36 of that diameter; phase spans one turn, small rotations stay within ±1/24 turn, alternating motifs reflect, centers shift by at most 0.22 cells, and alternating rows stagger by half a cell. Even the smallest box overlaps adjacent cells. Linework is serialized explicitly rather than emitted through an SVG <pattern> or <use> reference.

Voronoi grouping, clipping, and layers

Twenty-four deterministic sites form a jittered 6-by-4 grid in projected page space. Each field-cell center selects its nearest site. Site-to-motif mapping rotates by depth; at every depth each of the twelve motifs owns exactly two Voronoi regions. This creates broad neighborhoods of related line form while retaining local phase, reflection, and overlap.

The generated motif paths are not hard-clipped at the planar Voronoi boundary. They may overlap neighboring regions, which softens the group transition and permits intentional interference and moiré. Each path is clipped only by its Natural Earth depth polygon. The generator paints nested thresholds shallow to deep; before drawing each field it paints the common opaque pale ground through that threshold. Deeper thresholds therefore replace shallower artwork and produce exclusive visible bands without polygon differences.

bathymetry-hamonshu-metadata
defs
  12 bathymetry-hamonshu-clip-* clip paths
bathymetry-hamonshu
  bathymetry-0m
    bathymetry-0m-hamonshu-ground
    12 bathymetry-0m-hamonshu-variation-* groups
  bathymetry-200m
  ...
  bathymetry-10000m
bathymetry-hamonshu-key

Each variation path records the Izzi source ID, depth density and curvature, box factor, phase, rotation, reflection, offsets, two Voronoi site numbers, instance count, stroke paint, and opacity. Root metadata records source, projection, field geometry, nearest-site policy, absence of hard Voronoi clipping, blue-ramp contract, accepted moiré, and exact cell counts. Cahill–Keyes contains 1,269 cells per depth and 15,228 motif instances.

Commands and standard-pass behavior

Generate the six layered SVGs or all SVG/PDF/PNG artifacts with:

make generate-bathymetry-hamonshu
make generate-bathymetry-hamonshu-artifacts

One projection uses make generate-bathymetry-hamonshu-PROJECTION; for example:

make generate-bathymetry-hamonshu-cahill-keyes

The pass is included in make all, assets-single, assets-resilient, the Cahill–Keyes snapshot input set, and generation-profile "all". Profile selectors accept the canonical bathymetry-hamonshu and the convenience aliases hamonshu and art-agua-hamonshu.

The Stage 13 focused review artifacts are generated locally at assets.generated/cahill-keyes/svg/bathymetry-hamonshu-ck-44-22.svg and assets.generated/cahill-keyes/png/bathymetry-hamonshu-ck-44-22.png. They are deliberately not linked from GitHub Pages until a completed static-asset release publishes them to the immutable S3 tree.

Verification and limits

Focused tests validate the twelve monotonic depth parameter pairs, Izzi API bounds, twelve unique source IDs and path results, 24-site/equal-two-region distribution, overlap, identifiers, and exact 30% opacity. Each generator reopens its SVG and verifies the projection view box, metadata and counts, twelve geographic clips, 144 variation groups, depth paint order, source IDs, ground/clip references, hole preservation, finite path data, configured font, absence of SVG pattern definitions, and presence of all twelve Natural Earth blues.

The fields encode categorical depth thresholds, not continuous bathymetry. Hamonshū motif, density, curl, line direction, and moiré do not encode ocean current, swell, hazard, geology, uncertainty, or measured bottom roughness. Because every motif instance is serialized, large SVG/PDF files and substantial Inkscape export memory are accepted characteristics of this art pass.