robtfm a2992fcffd

Light Textures (#18031) ...

# Objective

add support for light textures (also known as light cookies, light
functions, and light projectors)


![image](https://github.com/user-attachments/assets/afdb23e2-b35f-4bf0-bf92-f883cd7db771)

## Solution

- add components:

```rs
/// Add to a [`PointLight`] to add a light texture effect.
/// A texture mask is applied to the light source to modulate its intensity,  
/// simulating patterns like window shadows, gobo/cookie effects, or soft falloffs.
pub struct PointLightTexture {
    /// The texture image. Only the R channel is read.
    pub image: Handle<Image>,
    /// The cubemap layout. The image should be a packed cubemap in one of the formats described by the [`CubemapLayout`] enum.
    pub cubemap_layout: CubemapLayout,
}

/// Add to a [`SpotLight`] to add a light texture effect.
/// A texture mask is applied to the light source to modulate its intensity,  
/// simulating patterns like window shadows, gobo/cookie effects, or soft falloffs.
pub struct SpotLightTexture {
    /// The texture image. Only the R channel is read.
    /// Note the border of the image should be entirely black to avoid leaking light.
    pub image: Handle<Image>,
}

/// Add to a [`DirectionalLight`] to add a light texture effect.
/// A texture mask is applied to the light source to modulate its intensity,  
/// simulating patterns like window shadows, gobo/cookie effects, or soft falloffs.
pub struct DirectionalLightTexture {
    /// The texture image. Only the R channel is read.
    pub image: Handle<Image>,
    /// Whether to tile the image infinitely, or use only a single tile centered at the light's translation
    pub tiled: bool,
}
```

- store images to the `RenderClusteredDecals` buffer
- read the image and modulate the lights
- add `light_textures` example to showcase the new features

## Testing

see light_textures example

2025-06-30 21:56:17 +00:00

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