What's the difference between modification of rotation in UCameraModifier::ModifyCamera and UCameraModifier::ProcessViewRotation?

When I went through code about UCameraModifier, I found that there’re two functions:

  • UCameraModifier::ModifyCamera
  • UCameraModifier::ProcessViewRotation

The first one will return a POV with a rotator, that I can change in override functions. And the latter one will directly return a rotator.

What’s the difference? For each function, what is the appropriate condition applied?