---
title: lightModelTwoSided
framework: GLKit
role: symbol
role_heading: Instance Property
platforms: [iOS 5.0+, iPadOS 5.0+, macOS 10.8+, tvOS 9.0+]
path: glkit/glkbaseeffect/lightmodeltwosided
---

# lightModelTwoSided

A Boolean value that indicates whether lighting is calculated for both sides of a primitive.

## Declaration

```swift
var lightModelTwoSided: GLboolean { get set }
```

## Discussion

Discussion If the value is GL_TRUE and the back face of a primitive is being rendered, the lighting values are calculated by negating the surface normals for the primitive. If the value is GL_FALSE, then the facing of the primitive is ignored when performing the lighting calculation. The default value is GL_FALSE. Setting the value of this property to GL_TRUE may impact performance. Only use two-sided lighting when either side of a primitive could theoretically be visible to the camera.

## See Also

### Configuring Lights

- [lightingType](glkit/glkbaseeffect/lightingtype.md)
- [material](glkit/glkbaseeffect/material.md)
- [lightModelAmbientColor](glkit/glkbaseeffect/lightmodelambientcolor.md)
- [light0](glkit/glkbaseeffect/light0.md)
- [light1](glkit/glkbaseeffect/light1.md)
- [light2](glkit/glkbaseeffect/light2.md)