Basic actor line of sight check for GZDoom.

//This is written for ZScript https://zdoom.org/wiki/ZScript

Class SightBlockChecker : LineTracer
{
    Bool BadLOF; //If true, there is something standing in the actors' line of fire.
    Actor Shooter; //The actor firing the raycast.
    Override ETraceStatus TraceCallback ()
    {
        Actor Mobj = Results.HitActor;

        //If the trace hit an actor that isn't the shooter, and has the specified token.
        //This would be better implemented with a custom flag on your actor instead of a token, but a token also allows this to work more universally, as stupid as it is.
        If (Results.HitType == Trace_HitActor && Mobj != Shooter && Mobj.FindInventory ("SightBlockToken",True))
        {
            BadLOF = True;
            Return Trace_Stop;
        }

        Return Trace_Skip;
    }
}

//Height offset is the height relative to the callers' position that the trace will be shot from.
//Range is how far the trace will go before it stops.
Bool A_CheckSightBlockers (Double HeightOffset = 32, Double Range = MaxTargetRange)
{
    Let Check = New ("SightBlockChecker");

    Vector3 Direction = (AngleToVector(Angle, Cos(Pitch)), -Sin(Pitch)); //Fire the ray at wherever the actor is facing.

    Check.Shooter = Self;
    Check.Trace ((Pos.X,Pos.Y,Pos.Z+HeightOffset),CurSector,Direction,MaxTargetRange,0);

    If (Check.BadLOF)
    {
        Check.Destroy();
        Return False;
    }
    Check.Destroy();
    Return True;
}