# Interpolation¶

Description

For all the Interpolation methods, the argument `t` is often `time` or `value`, though it can have other values, instead. If `t` is `time`, the interpolation between values happens over a duration. If `t` is `value`, then the expression maps one range of values to a new range of values.

For additional explanations and examples of the Interpolation methods, see JJ Gifford’s website.

Chris and Trish Meyer provide additional information and examples for these methods in an article on the ProVideo Coalition website.

Ian Haigh provides a script on After Effects Scripts website that you can use to easily apply advanced interpolation method expressions—such as bounces—to properties.

Andrew Devis provides a pair of video tutorials on the Creative COW website that show in detail how to use the linear expression method along with the Convert Audio To Keyframes command.

## linear(`t`, `tMin`, `tMax`, `value1`, `value2`)¶

Description

Returns `value1` when `t <= tMin`. Returns `value2` when `t >= tMax`. Returns a linear interpolation between `value1` and `value2` when `tMin < t < tMax`.

For example, this expression on the Opacity property causes Opacity values to ramp linearly from `20%` to `80%` over the time from `0` seconds to `6` seconds:

```linear(time, 0, 6, 20, 80)
```

This method—like all the Interpolation methods—can also be used to convert from one range of values to another.

For example, this expression on the Opacity property converts the Opacity values from the range `0%`-`100%` to the range `20%`-`80%`:

```linear(value, 0, 100, 20, 80)
```

Parameters

 `t` Number `tMin` Number `tMax` Number `value1` Number or Array `value2` Number or Array

Type

Number or Array

## linear(`t`, `value1`, `value2`)¶

Description

Returns a value that linearly interpolates from `value1` to `value2` as `t` ranges from `0` to `1`. Returns `value1` when `t <= 0`. Returns `value2` when `t >= 1`.

Parameters

 `t` Number `value1` Number or Array `value2` Number or Array

Type

Number or Array

## ease(`t`, `tMin`, `tMax`, `value1`, `value2`)¶

Description

Similar to linear with the same arguments, except that the interpolation eases in and out so that the velocity is `0` at the start and end points. This method results in a smooth animation.

Parameters

 `t` Number `tMin` Number `tMax` Number `value1` Number or Array `value2` Number or Array

Type

Number or Array

## ease(`t`, `value1`, `value2`)¶

Description

Similar to linear with the same arguments, except that the interpolation eases in and out so that the velocity is `0` at the start and end points. This method results in a smooth animation.

Parameters

 `t` Number `value1` Number or Array `value2` Number or Array

Type

Number or Array

## easeIn(`t`, `tMin`, `tMax`, `value1`, `value2`)¶

Description

Similar to ease, except that the tangent is `0` only on the `tMin` side and interpolation is `linear` on the `tMax` side.

Parameters

 `t` Number `tMin` Number `tMax` Number `value1` Number or Array `value2` Number or Array

Type

Number or Array

## easeIn(`t`, `value1`, `value2`)¶

Description

Similar to ease, except that the tangent is `0` only on the `value1` side and interpolation is `linear` on the `value2` side.

Parameters

 `t` Number `value1` Number or Array `value2` Number or Array

Type

Number or Array

## easeOut(`t`, `tMin`, `tMax`, `value1`, `value2`)¶

Description

Similar to ease, except that the tangent is `0` only on the `tMax` side and interpolation is `linear` on the `tMin` side.

Parameters

 `t` Number `tMin` Number `tMax` Number `value1` Number or Array `value2` Number or Array

Type

Number or Array

## easeOut(`t`, `value1`, `value2`)¶

Description

Similar to ease, except that the tangent is `0` only on the `value2` side and interpolation is `linear` on the `value1` side.

Parameters

 `t` Number `value1` Number or Array `value2` Number or Array

Type

Number or Array