# Smooth expression

From Castle Wiki

The **smooth** expression returns a value which is smoothed over time.

Given a number that changes over time, N(t), and a **smoothing** parameter, this expression updates its output Y each step with the following:

Y(0) = N(0)

Y(t) = Y(t - 1) + dt * (N(t) - Y(t - 1)) / smoothing