fullseye

circle_packing_apollonian — MATH construct op

使い方

Apollonian gasket from a Descartes quadruple — every circle a theorem.

Four mutually tangent circles satisfy the Descartes circle theorem

(k1 + k2 + k3 + k4)**2 == 2 * (k1**2 + k2**2 + k3**2 + k4**2)

where k = 1/r is the curvature (negative for the enclosing circle). The theorem is quadratic in k4, so a triple of mutually tangent circles has two solutions and the second is k4' = 2*(k1+k2+k3) - k4; recursing on that reflection fills the gasket. The centres follow the complex form k4*z4 = k1*z1 + k2*z2 + k3*z3 +- 2*sqrt(k1*k2*z1*z2 + ...), so no geometry is fitted — every circle is produced by an exact algebraic step.

★Why this earns its place: the drawing carries its own proof. Each circle can be checked against Descartes to machine precision, tangency is |z_i - z_j| == |r_i +- r_j| exactly, and an integral quadruple stays integral for ever — start from (-1, 2, 2, 3) and every curvature in the infinite packing is an integer (Lagarias-Mallows-Wilks). A drawing routine that is slightly wrong cannot keep integers integral.

Parameters

curvatures : 4 floats A Descartes quadruple. The default (-1, 2, 2, 3) is the smallest integral gasket. Must satisfy the theorem to 1e-9 relative. depth : int >= 0 Reflection levels. Level 0 is the four seed circles; each further level adds 4 * 3**(level-1), so the total is 2 * 3**depth + 2. min_curvature : float Drop circles smaller than 1/min_curvature (0 = keep all).

Returns a table: x, y, radius, curvature, depth (the enclosing circle has negative curvature and positive radius).

Raises ValueError: not four curvatures; the quadruple does not satisfy Descartes; every curvature negative or zero (no packing); depth negative or so large the packing exceeds the cap; non-finite input.

HALCON: no operator.

ファミリ共通の入力契約(fail-closed)

mathops の全 op は入力を検証してから計算する(黙って通さない):

詳しい使い方ガイド

参考(サンプルデータ・文献)

実行できる例(この op を実際に呼ぶ検証済みサンプル)

型が繋がる次の op(table を入力に取れる)

dynsys_poincare_section · dwt_inverse · chebyshev_eval_nd

同カテゴリ(construct)

ford_circles · phyllotaxis_pattern · neighbour_index_gaps · ifs_fractal · ifs_similarity_dimension · space_filling_curve · curve_locality


Provenance: mathops.py — MATH 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.