shadow_cast_2d — GFX2D light op

• 資料種類:image2d → image2d

• 呼叫:import gfx2d; gfx2d.shadow_cast_2d(occluder, x, y, steps=None, softness=0.0)(或 opsgfx2d.get("shadow_cast_2d"))

用法

每個像素相對 `(x, y) 點光源的可見性,作為 image2d`。

> 以下的詳細說明為原文 —— 摘要與標題已翻譯。

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.

參考(範例資料・文獻)

• 範例資料目錄(下載 URL / 授權) —— 2-D 用 skimage.data(BSD/公有領域)加合成圖,3-D 給出真實資料源(Stanford/PDS 等)的下載 URL。

• 運算子來歷與參考文獻 —— 該運算子族所依據的研究/方法出處。

• 演算法的正典(作者・年份)與用途見上面的族使用指南。

可執行的範例(實際呼叫該運算子並已驗證的樣例)

• gfx2d_scene — py -3.11 examples/gfx2d_scene.py

型別可銜接的下一個運算子(可接受 image2d 作為輸入)

dither

同類別(light)

radial_light · light_mask · normal_map_decode · normal_map_shade

*Provenance: gfx2d.py — GFX2D 運算子登記表。本條目由 tools/opdocs.py md 自動產生(請勿手動編輯)。*

© 2026 Kazufumi Furuse — Fullseye operator documentation. Licensed under Apache-2.0.