shadow_cast_2d — GFX2D light op

• 数据种类:image2d → image2d

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

用法

每个像素相对 `(x, y) 点光源的可见性,作为 image2d`。

> 以下的详细说明为原文 —— 摘要与标题已翻译。

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(示例数据・文献)

• 示例数据目录(下载 URL / 许可证) —— 2-D 用 skimage.data(BSD/公有领域)加合成图,3-D 给出真实数据源(Stanford/PDS 等)的下载 URL。

• 算子来历与参考文献 —— 该算子族所依据的研究/方法出处。

• 算法的正典(作者・年份)与用途见上面的族使用指南。

可运行的示例(实际调用该算子并已验证的样例)

• gfx2d_scene — py -3.11 examples/gfx2d_scene.py

类型可衔接的下一个算子(可接受 image2d 作为输入)

dither

同类别(light)

radial_light · light_mask · normal_map_decode · normal_map_shade

*Provenance: gfx2d.py — GFX2D 算子登记表。本条目由 tools/opdocs.py md 自动生成(请勿手工编辑)。*

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