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# roughness

The degree to which a material appears smooth, affecting both diffuse and specular response.

```
var roughness: MDLMaterialProperty { get }
```

## Discussion

At lower values, the material appears shiny, with well-defined specular highlights. At higher values, a diffuse material becomes retroreflective, and specular highlights are very spread out.

The default value is `0.9`, appearing mostly matte.

---

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