Getting serious about Main loop map/level control

UpAllNight

Hey guys, didn't really know where to ask this so I went for General. :0

My situation: To paint a picture - when you first start a new project in Gotdot and create your first Scene ( this I will call my Main.scene ), I want to use my Main.scene to handle all map/level changing and loading. Main.scene will contain all my logic code for the entire game. I want to load in and out pre-created map.tscn's and I also want to spawn mobs.tscn all from the main logic loop. In short, Main.scene controls the entire game, logic, input, mobs, etc..etc..

My question is, is there a way to 'append' a scene to a scene? I'm not sure how I should go about loading the level scene into my Main scene without unloading my Main scene which handles all the games logic.

Should I perhaps use Autoload and control my main game logic from scripts I feed into Autoload? Just use main.tscn to determine which map to load and unload etc. etc.. If I go that way, will code loaded through Autoload have access to variables and node handles from others scenes ? In other words, can I manipulate nodes loaded from other scenes in an Autoloaded atmosphere?

Hopefully this little diagram helps get my question across.

-Game Loads
-Autoloaded scripts load
-Main.tscn  loads and loads Map1 scene ( I assume Main.tscn is now unloaded ).
-Autoloaded Logic.script kicks in and handles gameplay logic, weather system, mob spawns.. etc
-Map1 scene has been completed, player won! Map1.scene unloads and Main.scene loads back up
-Main determines its time for Map2.scene, loads it and passes control to the newly loaded Map2 scene
-Autoload Logic.script kicks back in and handles game logic as it did for Map1.. etc.. 
-Wash and repeat.**

I'm nearing a crucial turn in my project and I got to get my foundation down before I go much further. Oh, and I've been Up All Night ! :)

Thank you !

cybereality

It depends how you want to code. There is no "correct" way. I don't use main loops anymore, though that is typically how game programming is taught. My games are all individual objects with their own behavior. Like autonomous agents. This makes the game more dynamic, and also allows for easier AI and physics code, since nothing really depends on each other. There is just a world, and things inhabit the world, doing their own thing, like real life. But the main loop method has some performance benefits and can make certain type of stuff easier.

In terms of your question, you can add levels (scenes) just like you add any other object. Basically anything in Godot can be a scene. So you use onready var to load the next level (using load() or preload()) then instance it with instance(), and finally add it to the scene tree (wherever you want) with add_child(). You also have to get rid of the old level with remove_child() and queue_free(). That's basically it.

UpAllNight

I see, you hit on some interesting approaches. I to wish to leave all code inside the individual actors myself but I just couldn't solve the problem of having to repeat a bunch of code.

For example,

Mob_a scene contains the mesh, all the effects, animation, sound and any visual extras that particular enemy would have. Now if I stuff all his AI behavior into the same scene as the mob I can edit just that scene and it'll change all Mob_a's in the game, which is good ! But my problem comes in with the next mob, Mob_b. This mob has all the characteristics of Mob_a but different mesh and skins and stats ( health, dmg, etc.. ) and he may have different abilities that Mob_a don't have. So dumping the Ai code into this mob wouldn't work as he thinks and acts differently. I'd basically have to write Ai loops for each mob type i have in game and further more have to change/edit every mob if something arises in the future.

I've been struggling with this concept since day one, I suppose I still have my head wrapped around the way other game engines I was brought up on did things ie: Main logic loop that runs through each actor per cycle. As long as I can reference and manipulate the external nodes then I see myself settling on a main logic loop, at least for the needs of the game project I have swimming around in my head.

cybereality

You would use OOP (object oriented programming). There would be a base class for an AI or Agent or whatever you want to call it, which just denotes that it is controlled by the computer. This will have some basic logic that all agents share, such as path finding, a finite state machine, collision detection, vision (like seeing the player or objects they may be interested in), etc. Then each enemy or character (like an NPC) would inherit from the Agent class and make their own version, like GoblinAgent, NPCAgent. And you could go down as many times as you want. So for NPCs you can have ShopOwnerAgent or BarTenderAgent, both of which inherit from NPCAgent, which inherits from the base Agent class. And each level can define their own specific behavior (like the bar keeper needs to know how to make drinks, and the shop owner may have specific dialogue to sell you an item at a discount, etc.). This is how most games work.