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What's your preferred way of letting objects affect the game?

Cornstalks · 2013-02-24T17:29:27

I try to program as atomically as possible, following the Single Responsibility Principle as best I can (but I don't go extreme nazi on things, in case you panic). This works pretty well in a lot of my work. But games are complicated. Objects interact with each other and the entire game's state regularly throughout the game. Units collide, one unit attacks another, a building makes units, a unit can create projectiles, and those projectiles can affect a large number of other units, etc. In other words, when programming this, you need a way for one object to be able to affect another object (or the game state itself, possibly by creating other units or projectiles). But it's not just a one-time case; many different units have different affects and interactions, which can result in messy code when trying to make all these possible interactions and events possible. What's your preferred way of letting various objects (units) affect the game (by creating other units, buildings, projectiles, hurting/healing other units, etc.)? I'm trying to think of some good ways to let these interactions occur that allows for (generally) clean code. My current solution is to have a Game class that actually runs a single game (by updating units (units update themselves as much as possible, but the Game tells them when to), enforcing game rules (so units can't walk up cliffs, for example), updating scores, etc.), and having each unit (or any other object that needs to interact with the Game itself) hold a reference to the Game to which it belongs. If a unit wants to do something that affects another unit or the Game, it calls the corresponding method on the Game object. For example, if unit A wants to create a building at x, y, it calls Game's makeBuilding(owning_player, x, y), and the Game either creates the building, or it returns false indicating that was an illegal move (perhaps there's already a building there). Or, for another example, unit B wants to launch a rocket that's aimed at target_x, target_y. Unit B then calls Game's createProjectile(owning_player, unit_pos_x, unit_pos_y, target_x, target_y), and the Game creates the projectile and takes ownership of it. Or, another example, unit C performs a melee attack at position x, y in direction dir, so it calls Game's meleeAttack(owning_player, x, y, dir) and the Game can decide if another (enemy) unit was hit and deal damage as needed. Is this a sane solution? Is there a better one? I'm afraid Game will grow into a monstrous class and have too much responsibility, but then again I'm not sure this can be avoided, and this solution will hopefully prevent a lot of spaghetti code and unnecessary coupling. I want to try and explore as many (good) solutions as I can before I get too far down the road with this game I'm working on.

General and Gameplay Programming Programming

Started by Cornstalks February 16, 2013 10:27 PM

19 comments, last by darkhaven3 11 years, 1 month ago

Sporniket

360

February 21, 2013 03:58 PM

In my recent game projects, I can relate my design to a company : game entitys (player, asteroids, aliens, laser beams,...) are under the care of a manager (PlayerManager, FlyingObjectsManager, BulletManager,etc...), that are under the care of the Main manager (Game)

Basically, the main manager tells the other managers to do their stuff or redraw their stuff when it's time, and the others manager tell their entity to update or redraw, and manages their group of entities (e.g. the flyingObjectManager spawns asteroids and bonus and recycle them when they go out of the screen).

When their should be an interaction between entities from different manager, it is carried by the main manager either procedurally (e.g. in my game loop retrieve a collection of flying objects/bullets from the corresponding manager, and ask the player manager if anything collides with a player), either event-driven (e.g., a player entity has collided with a bonus, the score must be updated and the bonus entity must be hidden).

Of course, my games are simple, so this level of details is adequate. For bigger projects, (e.g. an ARPG in an open world), their would be more levels of management, like in a big company.

Space Zig-Zag, a casual game of skill for Android by Sporniket-Studio.com

darkhaven3

160

February 24, 2013 05:29 PM

I can see this being a legitimate approach if and only if your game logic is heavily data-driven and validated by external tools prior to loading into the engine.

Really? All I can see is the many hundreds of ways this can crash and burn in a series of amusing ways... more so when you consider the follow up reply about not sanity checking the results...

Sure it can crash and burn if I care to introduce bad definitions in the frametable. Who cares? If the function called by a frame for a particular mobj_t says "You can't move here because I said so", then the mobj_t shouldn't give a damn. All that would happen is the mobj_t would stop moving in that direction, and possibly attempt to move in a different direction arbitrarily. It's not an mobj_t's responsibility to determine where it can move in this specific context; it's handled at a higher level. All an mobj_t is responsible for is itself, or being the target of another mobj_t in special cases (monster infighting, or the player being the target of a monster, mainly). And even in that case, mobj_t's typically don't care if they are targets of one another, and can't directly modify one another's target reference; they will attack one another until it is somehow resolved by other mechanics, typically by means of one mobj_t changing targets to the player or another monster, or entering its death state.

It seems simple and concise enough to be easy to debug and easy to implement, and it seems like it would be quite fast, especially in the context of a 2D sidescroller.

What's your preferred way of letting objects affect the game?

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What's your preferred way of letting objects affect the game?

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