shadow_cast_2d — GFX2D light op

• データ種: image2d → image2d

• 呼び出し: import gfx2d; gfx2d.shadow_cast_2d(occluder, x, y, steps=None, softness=0.0) (または 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

*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.