---
title: attenuationStartDistance
framework: modelio
role: symbol
role_heading: Instance Property
path: modelio/mdlphysicallyplausiblelight/attenuationstartdistance
---

# attenuationStartDistance

The distance from the light source, in units of local coordinate space, at which its illumination begins to diminish.

## Declaration

```swift
var attenuationStartDistance: Float { get set }
```

## Discussion

Discussion At distances less than the start distance, the light’s illumination is at full intensity. At distances greater than the end distance, the light provides no illumination. At distances in between the start and end distance, the attenuationFalloffExponent property defines the transition from full illumination to no illumination. The default distance is 1.0.

## See Also

### Managing Attenuation

- [attenuationEndDistance](modelio/mdlphysicallyplausiblelight/attenuationenddistance.md)