How can I get all actors in a camera's view frustum?

Okay, I though there were some collision cache. If not it may still be faster with my current implementation.

I’m working on an RTS game and have implemented a “box selection” feature. I.e. while holding down the mouse a box will be drawn, selecting all “units” under the box. At the moment I just iterate through all actors of a specific interface and check if they are inside or not.

Thought I should improve that solution by not checking against “units” off the screen, which impossibly could be selected.