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# scatteringFunction

The collection of material properties that define the material’s response to light.

```
var scatteringFunction: MDLScatteringFunction { get }
```

## Discussion

A [`MDLScatteringFunction`](/documentation/ModelIO/MDLScatteringFunction) object defines a Bidirectional Reflectance Distribution Function (BRDF), which determines how a material interacts with lighting to produce a surface appearance. Though you can access the individual material properties in a scattering function directly, a scattering function object lets you work with the collection of lighting-related material properties as a single unit. Use the [`MDLScatteringFunction`](/documentation/ModelIO/MDLScatteringFunction) class itself to describe a classical Lambertian/Blinn-Phong shading model, or the [`MDLPhysicallyPlausibleScatteringFunction`](/documentation/ModelIO/MDLPhysicallyPlausibleScatteringFunction) class to describe a shading model based more closely on real-world physics.

A scattering function determines lighting-related aspects of a material’s appearance, but not all aspects. For features such as opacity and surface deformation, use the methods listed in Working with individual material properties to access the corresponding material properties.

---

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