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();

     //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[] =
     {
         FVector(, , ),
         FVector(, , -),
         FVector(, -, ),
         FVector(, -, -),
         FVector(-, , ),
         FVector(-, , -),
         FVector(-, -, ),
         FVector(-, -, -)
     };

     //~~~

     //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();
         for (uint8 BoundsPointItr = ; BoundsPointItr < ; 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));
             }
         }
     }
 }