UE5 | Interfaces & Casting - Hierarchy 

Thank you, I'm glad you found it helpful. :) As for the pitched whine, I never actually noticed it so thank you for pointing it out. I currently use NVIDIA to record and audacity to normalize the volume so I'll be sure to check out some of the audio setting to hopefully removing it in any future videos.

In terms of casting, it's the class that is forced to be loaded if its not already loaded. Each object spawned from the class itself will then have additional data that is related to its unique instances variables. (different from the class default) This is why using base classes and hierarchy is important. Chances are you're core base classes would be loaded anyway so keeping them light weight (void of heavy assets such as textures, sounds etc) is vital to help ensure only what is actually been used is actually loaded. Plus it gives you more control on when something should be loaded when using soft references, of which can only really be utilized when you have good hierarchy. If I have an actor references (such as the example var) whilst I can store anything in it that is a child of actor, as long as I don't cast to anything, it means this specific class with the var inside won't have to force the class to be loaded. This instead would be off loaded to the class that actually spawns the actor. The third person character is probably a bad example as most people probably only have one character, meaning it would be loaded anyway.

@@mpattym either way the class is already loaded in memory so there is no reason for it to consume more memory. Like I said, the problem of using the size map is that the application is not running so it will calculate everything needed but that is not necessary the final memory usage. It has to be used as reference and not as the final value. I'm sure that if you run the game with either cast to the final class or cast to a base class then the memory usage will be the same.

@@fwannmacher the size map shows you what it has to load just to exist in the world whether it's being used or not. This is without specific instance data. This is how people can get into a situation where they have a single actor that loads everything in their game. (It's why casting is seen as bad) But this is resolved through good hierarchy. In essence, a class will load everything it thinks it'll need so it's ready.

because some people think that they have to ban casting and only use interfaces because it is heavy but they just don't know how to use it properly. Thats why he made this video :D

The difference between the act of casting and using an interface is negligible. As I mentioned in the video, the only thing to consider with casting is it's asset footprint it can create. And by asset footprint I mean assets that get forced to be loaded when they aren't actually being used. All of which is mitigated through using good class hierarchy. Adding to this, if you're not using interfaces correctly (using them to avoid casting), you can actually end up in a worse position than if you had just used casting to begin with. Being pretty active on various UE related discord channels, I've encountered many people (usually beginners) who end up doing convoluted interface setups just to try and avoid casting which is unnecessary.