tb_alpha_shape_boundary — 2D `typed` op

• Data kinds: points → signal

• Call: fullseye.apply(img, "tb_alpha_shape_boundary", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])

*No figure: this op takes points as input. A Studio program starting from an image cannot reach that type — see the runnable examples below for how it is used.*

Usage

Returns the boundary point indices via alpha shapes (point cloud → boundary points).

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

Delaunay 四面体分割の外接球半径 < 1/alpha の四面体の表面三角形(境界面)を集め、その頂点

集合を境界点とする。中実(表面+内部)の点群から表面殻の点だけを抜き出す用途に向く。

alpha を大きくすると許す半径 1/alpha が小さくなり、より密着した(細部を拾う)境界になる。

Parameters

----------

points : array_like (N,3)

alpha : float

正の実数。半径しきい値は 1/alpha。`estimate_alpha` で目安を得られる。

Returns

-------

boundary_point_indices : numpy.ndarray (K,) int64

points に対する境界点の index(昇順・重複なし)。境界が無ければ空配列。

2-D 進化レジストリへ橋渡しした 3d の op `alpha_shape_boundary。実装は同じで、呼び出し規約だけ op(v, a, b) に合わせてある。この op に調整点は無く、a も b` も使われない。

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)

• (none yet)

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

identity · tb_create_funct_1d_array · tb_smooth_funct_1d_gauss · tb_smooth_funct_1d_mean · tb_derivate_funct_1d · tb_integrate_funct_1d · tb_zero_crossings_funct_1d · tb_abs_funct_1d

Same category (`typed`)

tb_points_to_voxel · tb_estimate_point_normals · tb_iss_keypoints · tb_angle_3points · tb_project_points · tb_render_point_depth · tb_statistical_outlier_removal · tb_radius_outlier_removal

*Provenance: ops.py — 2D operator registry. This per-op note is generated by tools/opdocs.py md (do not hand-edit).*

tb_alpha_shape_boundary — 2D typed op