Learning BYOND, Day 6: Open Heart Surgery

I’m probably going to go back and severely edit those “Learning BYOND” entires. Right now they’re a somewhat rambling collection that probably contain a number of inadvertent lies said out of code-newbie innocence. I’m not sure anyone finds those entries particularly interesting… at the very least, I should throw in some helpful diagrams!

Diagrams like so.

Diagrams like so. Funny enough, knowing how to answer the Pythagorean Theorem is actually quite useful for aspiring BYOND users (although the get_dist() function performs much the same way).

Oh well, this entry will be somewhat more interesting, I hope. Today, I talk about what goes into coding a force that drives a virtual universe.

The heart of my game is the actionqueue procedure. This is activated when the world first boots up and stays running for the duration. Every second, it cycles through a list of designated “alive” mobs and checks the action queue on each. Each mob in the game can only execute one action per turn. In this way, BYOND’s flexible engine has been shaped into a simulated turn-based roleplaying game engine.

Controlling the use of the actionqueue is tricky because (thanks to the sleep() proc within it) it is waiting while other procedures are occurring at the same time. To protect against the conflicts that may occur, the actionqueue only performs the first action in the queue. No other procedure should manipulate that first action. Otherwise, if the timing is just right (or just wrong) then something’s going to break. If something needs to be inserted before that first action, the actionqueue procedure is the one to handle this.

The actionqueue procedure must be very efficient. I’ve tested that my computer can run about 50,000 lines per second. If I have 50 objects and the ActionQueue wants to go through 1000 lines each, it’ll bog down the server. If, on the other hand, each object only processes 10 lines then I can support up to 5000 idling objects. (Give or take — this is a bit of a shot in the dark.) If the server’s lagging, there will be a visible hitch every second when the actionqueue goes through its list.

Sorry Q-Bot, Ive made my own.

Sorry Q-Bot, I've made my own.

How many “living” objects will I need? It’s hard to say. Though my plan is not set in stone, currently I want to do an epic 1000×1000 2d tile-based world. That’s huge – traveling at one second per square, it’ll take about 16 1/2 minutes to cross the length of it. (I’ll probably add quicker means to travel.)

However, on such a large map, will there will always be something fairly meaningful going on with the players will be in the thick of it? This brings us to the central point: a huge world is pointless in game mechanic terms. Where the player is is not half as important as what I give them to do.

With the implementation of the actionqueue, I’ve harnessed BYOND’s flexible event model into a powerful virtual heart that drives my ideal game. In the coming days, I’ll have to design and implement the virtual soul that engages the player. It’s a pretty tall order – hopefully my 25 years of playing games will grant some insight there.

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