This Effect can layer on other effects to keep their brightness within a particular range

This gives effects global information about the frame, before and after rendering pixels. This
can make some effects more convenient to write, and it allows effects to keep track of global per-pixel
data if they need to.

Also allows particle lifetime to be dynamic again.

Woo, 355 keyframes per second.

This is a big file, let's not include it in the distribution by default.
The script itself is the part that makes an interesting example.