If I have something like this:

```
y = sin(x+z)
```

How can I plot the values of y, as a function of x and all the possible values of z in [-0.1, +0.1]?

That is, I want the area defined by those limits. So everything bounded by sin(x-0.1) and sin(x+0.1) would be shaded, everything outside would be whitespace.

I'm trying to express this in gnuplot, but any software would probably be fine.