Ue4中的框选函数

void AHUD::GetActorsInSelectionRectangle(TSubclassOf<class AActor> ClassFilter, const FVector2D& FirstPoint, const FVector2D& SecondPoint, TArray<AActor*>& OutActors, bool bIncludeNonCollidingComponents, bool bActorMustBeFullyEnclosed)
{
    // Because this is a HUD function it is likely to get called each tick,
    // so make sure any previous contents of the out actor array have been cleared!
    OutActors.Empty();

    //Create Selection Rectangle from Points
    FBox2D SelectionRectangle(0);

    //This method ensures that an appropriate rectangle is generated, 
    //        no matter what the coordinates of first and second point actually are.
    SelectionRectangle += FirstPoint;
    SelectionRectangle += SecondPoint;


    //The Actor Bounds Point Mapping
    const FVector BoundsPointMapping[8] =
    {
        FVector(1, 1, 1),
        FVector(1, 1, -1),
        FVector(1, -1, 1),
        FVector(1, -1, -1),
        FVector(-1, 1, 1),
        FVector(-1, 1, -1),
        FVector(-1, -1, 1),
        FVector(-1, -1, -1)
    };

    //~~~

    //For Each Actor of the Class Filter Type
    for (TActorIterator<AActor> Itr(GetWorld(), ClassFilter); Itr; ++Itr)
    {
        AActor* EachActor = *Itr;

        //Get Actor Bounds                //casting to base class, checked by template in the .h
        const FBox EachActorBounds = Cast<AActor>(EachActor)->GetComponentsBoundingBox(bIncludeNonCollidingComponents); /* All Components? */

        //Center
        const FVector BoxCenter = EachActorBounds.GetCenter();

        //Extents
        const FVector BoxExtents = EachActorBounds.GetExtent();

        // Build 2D bounding box of actor in screen space
        FBox2D ActorBox2D(0);
        for (uint8 BoundsPointItr = 0; BoundsPointItr < 8; BoundsPointItr++)
        {
            // Project vert into screen space.
            const FVector ProjectedWorldLocation = Project(BoxCenter + (BoundsPointMapping[BoundsPointItr] * BoxExtents));
            // Add to 2D bounding box
            ActorBox2D += FVector2D(ProjectedWorldLocation.X, ProjectedWorldLocation.Y);
        }

        //Selection Box must fully enclose the Projected Actor Bounds
        if (bActorMustBeFullyEnclosed)
        {
            if(SelectionRectangle.IsInside(ActorBox2D))
            {
                OutActors.Add(Cast<AActor>(EachActor));
            }
        }
        //Partial Intersection with Projected Actor Bounds
        else
        {
            if (SelectionRectangle.Intersect(ActorBox2D))
            {
                OutActors.Add(Cast<AActor>(EachActor));
            }
        }
    }
}