Making a look-at trigger through a camera

Questions & Answers
1

Hey, So i have been really stuck on how i should go about making something trigger if i look at it / look away in the cameras view… What would be the easiest way?

I was thinking using Raycasts?

2

The Dot product is perfect for this sort of thing.
Some pseudo:

Vec3 dirFromMeToObject = (objPos - myPos).normal
Vec3 myCurrentFacingDir = trans.forward

if (Vec3.Dot(dirFromMeToObject, myCurrentFacingDir) > 0)
    //object is with a 180 degree arc in front of us

if (Vec3.Dot(dirFromMeToObject, myCurrentFacingDir) > 0.5)
    //object is with a 90 degree arc in front of us

if (Vec3.Dot(dirFromMeToObject, myCurrentFacingDir) > 0.75)
    //object is with a 45 degree arc in front of us