terrain op• データ種: mesh → mesh
• 呼び出し: import fullseye as fs; fs.ledger.mesh_subdivide(V, F, *, levels: 'int' = 1, target_edge=None, max_faces: 'int' = 4000000) (実装を直接呼ぶなら import render3d; render3d.mesh_subdivide(V, F, *, levels: 'int' = 1, target_edge=None, max_faces: 'int' = 4000000)、台帳から引くなら ops3d.get("mesh_subdivide"))
Refine a triangle mesh → `(V, F): uniform midpoint subdivision (levels` passes,
×4 faces each) or adaptive tessellation to a target edge length (`target_edge`:
median edge = target, edge segments ≤ 1.5×target, in-face Delaunay edges < 2×target).
The geometry is *unchanged* — every new vertex lies on an old facet, so surface area
and enclosed volume are preserved exactly (tests pin this) and nothing is ever
decimated; only the facet size changes, so a later :func:mesh_displace_spectrum can
carry short wavelengths without aliasing.
Adaptive mode cuts each edge into `n = round(length / target_edge)` (≥ 1) segments
— a per-*edge* count, hence conforming across neighbours (no T-junctions) — and fills
each face with a **hexagonal lattice at spacing `target_edge` in the face plane**,
triangulated by a per-face 2-D Delaunay (Qhull). The interior therefore has edges
≈ `target_edge` *whatever the shape of the source face* (the Gaskell Itokawa faces
have a median longest/shortest edge ratio of 1.83, so a per-face lattice pattern
inherits that anisotropy; repeated midpoint bisection additionally leaves a factor-2
spread `(target/2, target]`). Measured on the Itokawa model (edge p5/median/p95 =
2.6/4.7/7.2 m, target 1.5 m): see `examples_3d/itokawa_regolith_hero.py` — the test
pins p95/p5 ≤ 1.5 on a graded plane. `max_faces` (default
`MAX_SUBDIVIDE_FACES`) is a memory guard: if the plan would exceed it the call
raises `ValueError` (fail-closed) rather than silently under-refining.
Deterministic. Fail-closed: degenerate mesh, `levels < 0`, non-positive
`target_edge / caps → ValueError`.
2 つのモードがあり、`target_edge` の有無で切り替わる。
• `target_edge=None(一様): 全辺を中点で割る細分を levels` 回繰り返す(面数は
1 回ごとに 4 倍)。`levels=0 は入力をそのまま返す。各回の前に 面数×4 > max_faces`
なら `ValueError`。
• `target_edge 指定(適応): 辺ごとに分割数 n = round(長さ / target_edge)`
(最小 1)を決め、隣接面で共有するので T 字接合は出ない。分割数は内部上限 64 に
無言でクランプ されるため、`target_edge` の 64 倍を超える長さの辺は目標に届かない。
どの辺も分割不要なら入力のコピーを返す。面数の見積り
`Σ(3 辺の分割数の和 + 平均分割数²) が max_faces` を超えると計算前に
`ValueError。levels` はこのモードでは使わない。
返り値 `(V (N',3) float64, F (M',3) int64)`。新頂点は必ず元の面の上に置くので面積と
体積は変わらない(平滑化ではない)。適応モードは面ごとに 2-D Delaunay(scipy Qhull)を
使うので、極端に細長い面では品質が落ちる。細分後に `mesh_edge_lengths` で辺長分布を
確かめ、`mesh_displace_spectrum` へ渡す。
• サンプルデータ カタログ(DL URL / ライセンス) — 2-D は skimage.data(BSD/public)+ 合成、3-D は実データ源(Stanford/PDS 等)の DL URL。
• 演算子の来歴・参考文献 — この op 族の元になった研究/手法の出典。
• itokawa_regolith_hero — py -3.11 examples_3d/itokawa_regolith_hero.py
mesh を入力に取れる)mesh_to_voxel · mesh_to_points · to_points · fuse_to_voxel · ambient_occlusion · cast_shadow · supersample_mesh · render_beauty
terrain)mesh_displace_fbm · terrain_region_mask · mesh_scatter_boulders · mesh_edge_lengths · displacement_band_weights · mesh_displace_spectrum · bump_normals_fbm
*Provenance: render3d.py — 3D operator registry. この per-op ノートは tools/opdocs.py md が自動生成(手編集しない)。*
© 2026 Kazufumi Furuse — Fullseye operator documentation. Licensed under Apache-2.0.