What is the preferred methods for doing so, performance-wise?
For example I want to pick certain objects in an area around a given point.
What I have thought off so far is using invisible objects as extended hit detectors. Like creating a circle or square then have collision responses to them.
Or maybe just pass the entire object list and iterate on it, then using a distance/angle based condition.
If you have a physics engine that is already capable of efficiently finding collisions between bounding shapes, generating a temporary shape (like a sphere) is common practice. If the physics engine has support for single-frame shape-collision queries, you could use that, but many will require you to create a new physics collision shape and then remember to remove it yourself after the next physics update.
You might want the object to exist more than one frame anyhow, for example maybe the effect you're looking for is to damage every enemy in contact with the explosion at 100 dmg/sec with the explosion lasting 3 seconds, so enemies can enter or leave the explosion and get less than the full 300 dmg it could do.
