fullseye

shadow_cast_2d — GFX2D light op

• データ種: image2d → image2d
• 呼び出し: import fullseye as fs; fs.ledger.shadow_cast_2d(occluder, x, y, steps=None, softness=0.0) (実装を直接呼ぶなら import gfx2d; gfx2d.shadow_cast_2d(occluder, x, y, steps=None, softness=0.0)、台帳から引くなら opsgfx2d.get("shadow_cast_2d"))

使い方

Visibility of every pixel from a point light at (x, y), as image2d.

Ray-marches the segment from each pixel to the light, sampling occluder (2-D, [0, 1], 1 = fully blocking) at steps points with nearest lookup, and returns 1 - max(occluder along the ray). For a binary occluder that is exactly 0 or 1 — no tolerance involved.

The sample excludes the pixel itself, so an occluder is lit on its own light-facing surface and casts behind itself.

softness > 0 blurs the visibility map by that sigma afterwards, which is a penumbra-shaped lie rather than a penumbra: a real one widens with distance from the occluder. It is offered because it looks right and named so it cannot be mistaken for physics.

steps defaults to the image diagonal, which samples about once per pixel. An occluder thinner than the step spacing can be missed; that is the honest limit of a fixed-step march and the reason steps is an argument.

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(image2d を入力に取れる)

dither

同カテゴリ(light)

radial_light · light_mask · normal_map_decode · normal_map_shade

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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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