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# blinn

Shading that incorporates ambient, diffuse, and specular properties, where specular highlights are calculated using the Blinn-Phong  formula.

```
static let blinn: SCNMaterial.LightingModel
```

## Discussion

The Blinn-Phong approximation of real-world reflectance calculates the color of a point on a surface using the following formula:

```objc
color = ambient * al + diffuse * max(0, dot(N, L)) + specular * pow(max(0, dot(H, N)), shininess)
```

Some terms refer to the material’s properties: [`ambient`](/documentation/SceneKit/SCNMaterial/ambient), [`diffuse`](/documentation/SceneKit/SCNMaterial/diffuse), [`specular`](/documentation/SceneKit/SCNMaterial/specular), and [`shininess`](/documentation/SceneKit/SCNMaterial/shininess). The other terms are as follows:

- `al`: The sum of all ambient lights in the scene (a color).
- `N`: The surface normal vector at the point being shaded, as supplied by the geometry’s vertex data, interpolated between vertices, and possibly modified by the material’s [`normal`](/documentation/SceneKit/SCNMaterial/normal) property.
- `L`: The (normalized) vector from the point being shaded to the light source.
- `H`: A vector halfway between the light vector `L` and the (normalized) eye vector `E` (the vector from the point being shaded to the viewer), calculated using the formula `H = normalize(L + E)`.

---

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