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Specify light() only runs for pixels affected by light #12174

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3 changes: 3 additions & 0 deletions tutorials/shaders/shader_reference/spatial_shader.rst
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Expand Up @@ -547,6 +547,9 @@ the ``unshaded`` render mode. If no light function is written, Godot will use th
written to in the ``fragment()`` function to calculate the lighting for you (subject to the render mode).

The ``light()`` function is called for every light in every pixel. It is called within a loop for each light type.
Keep in mind the ``light()`` function only runs for pixels that are affected by at least one light source, and is
completely skipped for pixels that are not hit by any light and shadow. You can use this to create different behavior for
lit and unlit pixels in your shader.
Comment on lines +550 to +552

@Arecher Arecher Jul 27, 2026 •
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Keep in mind the ``light()`` function only runs for pixels that are affected by at least one light source, and is
completely skipped for pixels that are not hit by any light and shadow. You can use this to create different behavior for
lit and unlit pixels in your shader.
The ``light()`` function is only guaranteed to run for pixels that are affected by at least one light source, and
*might* be completely skipped by the renderer for pixels that are not hit by any light or shadow at all.

Not sure if this addition (even with changes to make it more accurate) is worthwhile of being added to the docs anymore though, since it's a little vague and not directly applicable.


Below is an example of a custom ``light()`` function using a Lambertian lighting model:

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