The inability to modify camera projection matrices in blueprint (and the extreme difficulty of doing it in C++) puts a big damper on several very creative effects.
Exposing the FMatrix on a camera lets us do fun off-axis projections like this:
Additionally, proper Portals and Mirrors may be implemented as well.
A blueprint node that allows for the creation and modification of arbitrary FMatrix objects and their application to Cameras and SceneCapture2D actors would be great to this end.
(It’s important they’re FMatrix objects and not FPerspectiveMatrix objects since FPerspectiveMatrix doesn’t support off-axis projection).