Can be used to create a effect that simulates pain or poisoning. Especially useful when used with volumes. You could set up a “frost” effect on your Global volume, and create local volumes around say… barrels of fire, that override the “Size” parameter.
A grayscale texture can be used to improve this effect. A few examples are included in the SC Post Effects/_Examples/Overlays folder.
In order for the “Size” parameter to work as intended, your texture must have white values between 0 and 1. The parameter interpolates between these values, making the texture appear to grow towards the center of the screen.