---
title: MDLMaterialSemantic.interfaceIndexOfRefraction
framework: modelio
role: symbol
role_heading: Case
path: modelio/mdlmaterialsemantic/interfaceindexofrefraction
---

# MDLMaterialSemantic.interfaceIndexOfRefraction

The index of refraction for the medium surrounding a material.

## Declaration

```swift
case interfaceIndexOfRefraction
```

## Discussion

Discussion This value corresponds to the n1 parameter in Schlick’s equation for approximating Fresnel reflection effects. Typically, one assumes a the medium surrounding a material is air or empty space, so a value of 1.0 suffices for most uses of this semantic.

## See Also

### Constants

- [MDLMaterialSemantic.baseColor](modelio/mdlmaterialsemantic/basecolor.md)
- [MDLMaterialSemantic.subsurface](modelio/mdlmaterialsemantic/subsurface.md)
- [MDLMaterialSemantic.metallic](modelio/mdlmaterialsemantic/metallic.md)
- [MDLMaterialSemantic.specular](modelio/mdlmaterialsemantic/specular.md)
- [MDLMaterialSemantic.specularExponent](modelio/mdlmaterialsemantic/specularexponent.md)
- [MDLMaterialSemantic.specularTint](modelio/mdlmaterialsemantic/speculartint.md)
- [MDLMaterialSemantic.roughness](modelio/mdlmaterialsemantic/roughness.md)
- [MDLMaterialSemantic.anisotropic](modelio/mdlmaterialsemantic/anisotropic.md)
- [MDLMaterialSemantic.anisotropicRotation](modelio/mdlmaterialsemantic/anisotropicrotation.md)
- [MDLMaterialSemantic.sheen](modelio/mdlmaterialsemantic/sheen.md)
- [MDLMaterialSemantic.sheenTint](modelio/mdlmaterialsemantic/sheentint.md)
- [MDLMaterialSemantic.clearcoat](modelio/mdlmaterialsemantic/clearcoat.md)
- [MDLMaterialSemantic.clearcoatGloss](modelio/mdlmaterialsemantic/clearcoatgloss.md)
- [MDLMaterialSemantic.emission](modelio/mdlmaterialsemantic/emission.md)
- [MDLMaterialSemantic.bump](modelio/mdlmaterialsemantic/bump.md)