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# constant

Uniform shading that incorporates ambient lighting only.

```
static let constant: SCNMaterial.LightingModel
```

## Discussion

This shading model calculates the color of a point on a surface with the following formula:

```objc
color = ambient * al + diffuse
```

The [`ambient`](/documentation/SceneKit/SCNMaterial/ambient) and [`diffuse`](/documentation/SceneKit/SCNMaterial/diffuse) terms refer to the material’s properties. The `al` term is the sum of all ambient lights in the scene (a color).

---

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