---
title: envelope
framework: phase
role: symbol
role_heading: Instance Property
path: phase/phasemappedmetaparameterdefinition/envelope
---

# envelope

A collection of line segments that curve and connect to form a graph.

## Declaration

```swift
var envelope: PHASEEnvelope { get }
```

## Discussion

Discussion The line segments collectively plot an output value for the inputMetaParameterDefinition property. To plot the input, call evaluate(x:), passing in the input metaparameter’s value. To gradually change the input over time, call fade(value:duration:).