---
title: roughness
framework: modelio
role: symbol
role_heading: Instance Property
path: modelio/mdlphysicallyplausiblescatteringfunction/roughness
---

# roughness

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

## Declaration

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

## Discussion

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.

## See Also

### Working with Shading Properties

- [subsurface](modelio/mdlphysicallyplausiblescatteringfunction/subsurface.md)
- [metallic](modelio/mdlphysicallyplausiblescatteringfunction/metallic.md)
- [specularAmount](modelio/mdlphysicallyplausiblescatteringfunction/specularamount.md)
- [specularTint](modelio/mdlphysicallyplausiblescatteringfunction/speculartint.md)
- [anisotropic](modelio/mdlphysicallyplausiblescatteringfunction/anisotropic.md)
- [anisotropicRotation](modelio/mdlphysicallyplausiblescatteringfunction/anisotropicrotation.md)
- [sheen](modelio/mdlphysicallyplausiblescatteringfunction/sheen.md)
- [sheenTint](modelio/mdlphysicallyplausiblescatteringfunction/sheentint.md)
- [clearcoat](modelio/mdlphysicallyplausiblescatteringfunction/clearcoat.md)
- [clearcoatGloss](modelio/mdlphysicallyplausiblescatteringfunction/clearcoatgloss.md)