terrain_region_mask — 3D `terrain` op

• Data kinds: mesh → signal

• Call: import fullseye as fs; fs.ledger.terrain_region_mask(V, F, *, smooth_fraction: 'float' = 0.3, method: 'str' = 'neck', seed: 'int' = 0) -> 'np.ndarray' (to call the implementation directly, import render3d; render3d.terrain_region_mask(V, F, *, smooth_fraction: 'float' = 0.3, method: 'str' = 'neck', seed: 'int' = 0) -> 'np.ndarray'; from the registry, ops3d.get("terrain_region_mask"))

Usage

Per-face terrain weights (M,) in [0,1]: 0 = smooth regolith "sea", 1 = rough highland.

> The detailed description below is the original text — the summary and the headings are translated.

`method='neck'` (default, Itokawa-motivated): the sea is the band of faces around the

narrowest cross-section along the principal (long) axis — MUSES-C Regio sits in the neck

between head and body — widened until it covers `smooth_fraction` of the surface area.

`method='noise'`: low-frequency seeded fBm thresholded at the area-weighted

`smooth_fraction quantile (generic patches). method='slope'`: faces are ranked by

local slope (angle between face normal and the smoothed neighbourhood normal); the

flattest `smooth_fraction` of the area is sea. Deterministic; fail-closed on bad input.

返り値は面ごとの float64 `(M,)` で値は 0 か 1 の二値(中間値は出ない)。手順は

`method` ごとにスコアを 1 つ作り、スコアの小さい面から面積を累積して全面積の

`smooth_fraction` に達するまでを「海」(0)にする。

• `'neck'`: 面重心の面積重み付き主軸(SVD 第 1 成分)に沿って、主軸座標の 20〜80 %

区間を 24 ビンに切り、各ビンの半径 90 percentile が最小のビン中心を「くびれ」とし、

くびれ面からの距離をスコアにする。8 面未満のビンは無視。`seed` は使わない。

• `'noise': 面重心での :func:fbm_noise`(波長 = 境界箱対角 / 3、2 オクターブ、

`seed`)をスコアにする。

• `'slope'`: 面法線と「3 頂点の頂点法線平均」のなす角(ラジアン)をスコアにする。

`seed` は使わない。

`smooth_fraction は [0, 1] (範囲外・非有限は ValueError`)。0 なら全面 1、1 なら

全面 0 を即返す。`method が上記以外なら ValueError`。得た重みは

`mesh_scatter_boulders / sample_boulders の region_weights` に渡して海に岩を

置かないようにする用途。

References (sample data, literature)

• Sample-data catalog (download URLs / licences) — 2-D uses skimage.data (BSD/public domain) plus synthetic images; 3-D lists download URLs for real data sources (Stanford, PDS, …).

• Operator provenance and references — the sources of the research/methods this op family came from.

Runnable examples (verified samples that actually call this op)

• itokawa_regolith_hero — py -3.11 examples_3d/itokawa_regolith_hero.py

Ops the type connects to (they accept `signal` as input)

fuse_to_voxel

Same category (`terrain`)

mesh_displace_fbm · mesh_scatter_boulders · mesh_edge_lengths · mesh_subdivide · displacement_band_weights · mesh_displace_spectrum · bump_normals_fbm

*Provenance: render3d.py — 3D operator registry. This per-op note is generated by tools/opdocs.py md (do not hand-edit).*

terrain_region_mask — 3D terrain op