fullseye

particle_step — GFX2D particle op

• データ種: table → table
• 呼び出し: import fullseye as fs; fs.ledger.particle_step(state, dt, gravity=(0.0, 98.0), drag=0.0) (実装を直接呼ぶなら import gfx2d; gfx2d.particle_step(state, dt, gravity=(0.0, 98.0), drag=0.0)、台帳から引くなら opsgfx2d.get("particle_step"))

使い方

Advance a particle state by dt seconds. Returns a new dict.

Semi-implicit (symplectic) Euler::

v <- v + (g - drag*v) * dt
p <- p + v * dt
age <- age + dt

which makes the closed form exact and checkable: with gravity=(0,0) and drag=0 the position after k steps is p0 + v0*k*dt, and with drag the speed is v0 * (1 - drag*dt)**k. Both are compared as equalities in the test suite.

gravity is (gx, gy) in px/s^2, positive gy pulling down the screen. The input dict is never mutated.

Raises ValueError: dt <= 0; drag * dt >= 1, which is the point where explicit drag stops decaying the speed and starts reversing it — an instability that otherwise shows up as particles flying backwards rather than as an error.

参考(サンプルデータ・文献)

• 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。
• アルゴリズムの正典(著者・年)と用途は上記ファミリ使い方ガイドに記載。

実行できる例(この op を実際に呼ぶ検証済みサンプル)

• gfx2d_scene — py -3.11 examples/gfx2d_scene.py

型が繋がる次の op(table を入力に取れる)

layer_stack · particle_render

同カテゴリ(particle)

particle_emit · particle_render

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Provenance: gfx2d.py — GFX2D 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.

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