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# lambert

Shading that incorporates ambient and diffuse properties only.

```
static let lambert: SCNMaterial.LightingModel
```

## Discussion

This shading model is based on Lambert’s Law of diffuse reflectance, calculating the color of a point on a surface with the following formula:

```objc
color = ambient * al + diffuse * max(0, dot(N, L))
```

The [`ambient`](/documentation/SceneKit/SCNMaterial/ambient) and [`diffuse`](/documentation/SceneKit/SCNMaterial/diffuse) terms refer to the material’s properties. The other terms are as follows:

- `al`: The sum of all ambient lights in the scene (a color).
- `N`: The surface normal vector at the point being shaded, as supplied by the geometry’s vertex data, interpolated between vertices, and possibly modified by the material’s [`normal`](/documentation/SceneKit/SCNMaterial/normal) property.
- `L`: The (normalized) vector from the point being shaded to the light source.

---

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