#implementation vs concept

[askagamedev]

All that stuff about making Super AI was Super Interesting, but how is the normal not-playing-games-against-itself-to-try-and-win AI designed & developed?

Ok, so… Game AI is a really deep subject. Like… deep enough that there are professional engineers and designers who are employed full time to make this sort of thing happen. I can’t do the entire subject justice in a small post I threw together in one evening. So instead, you’ll all get a multi-part series on the topic because it’s something I find fun. 

Let’s take a look at the eagle-eye view of the topic.

Developing Game AI (Part 1)

Normal game AI is definitely different from experimental/theoretical AI. Experimental AI like Deep Blue, AlphaGO, the UC Berkeley Overmind, or OpenAI are developed to see how far computer learning can go. Game AI is primarily geared towards providing a fun experience for the player. This can have some amount of overlap with experimental AI, but the fundamental goals are different, which necessitates different design and implementation. From the very beginning, we developers establish ground rules for what the AI is supposed to do, as well as its limitations. We have to answer questions like:

Does the AI represent an equal opponent for the player? (E.g. Hearthstone, Chess, Street Fighter)

Will the player fight many AIs at once? Is the AI effectively disposable? (E.g. Dynasty Warriors, Doom)

Will the AI need to cooperate with the player? (e.g. Mass Effect, StarCraft)

Will the AI need to cooperate/interact with other AI? (e.g. Fallout, Skyrim)

Will the AI need to navigate non-uniform terrain? (e.g. Uncharted)

One of the bigger factors to the answers to these questions is how long (we think) it will take us to actually implement these things. We are, after all, always on a schedule. Complicated and extensible AI is great, but not if we can’t fit it into the schedule or budget. Once we figure out the limits of what the AI is supposed to do, we begin with rudimentary design and implementation.

AI development is generally broken into two separate parts - getting the AI to make a choice, then actually executing that choice. These two parts can be (and often are) developed independently of each other. 

Making the choice would be figuring out which card to play, which spell to cast, or which ally to heal. Typically, this involves some sort of prioritization system, where the AI evaluates potential options and chooses one based on some set of established rules. Is attacking more worthwhile than using a spell? How about using an item? Should the AI try to maximize its use of mana per turn for tempo, or should it try to maximize card advantage? Which enemy should the AI target for this attack? The most dangerous one? The one with lowest HP? And how do you quantitatively define “most dangerous” anyway?

Executing the choice is the less sexy, but incredibly important part that most fans don’t think about. In fact, most of the design and implementation time for AI in games is often spent making the execution work. After the AI chooses which spell to cast, how does it actually do it? The AI probably has to move into range, which requires pathfinding. The AI has to cast the spell, which means that it can’t be taking damage, unconscious, silenced, etc. The AI might have to consider environmental hazards when pathfinding. The AI might have to consider its location in the world - say that the player is trying to kite an enemy out of its home base, but the game must stream the environment from the disc. If the player goes too far from the enemy base, it will get unloaded from system memory, and likely take enemy with it. How do we handle such cases?

In addition to that, in many games there’s also an even lower level of AI that often needs to work as well. At its most basic level, the character animation system is governed by AI as well. If the player shoots an enemy, it probably needs to play some sort of take-damage reaction, right? How does the enemy know to do that? Something has to prioritize which animations are playing when, and which take priority over what. Dying usually trumps climbing a ladder or casting a spell. There’s generally an AI that handles what animations a character needs to be playing, and when to transition from one animation to another. Remember, the machine doesn’t have any inherent concept of matching motions or positions or anything; any sort of animation transition must come from some sort of set of rules that we create. That also includes keeping track of states like death, unconscious, aggression, snared, which direction to face, etc. and that AI must be able to override or pause the higher order functions too. After all, the AI shouldn’t be trying to navigate to a point on the map if it’s dead.

Building these sorts of systems require a lot of thought and work. The vast majority of developing game AI is spent solving these kind of core problems on a system-wide level. Things like emulating a personality or adding polish touches often come super late (if at all) in the development cycle, simply because getting the core elements to work requires so much time, effort, and iteration. AI can be as simple or deep as we want, but the very basic stuff requires a lot of work to set up.

Next time, I’ll talk about how we get AI to evaluate choices.

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[askagamedev]

Hi Dev. I have an important question. How do you know if an idea is good? I'm paranoid to really tell people a lot about mine because I'm paranoid they think its going to be stupid. I tell my family but my paranoia leads me to believe they could be patronizing without knowing it. So how do you know? Or is it just subjective? If I were to pitch them one day would they be laughed at?

My litmus test for whether an idea has merit has always been to ask myself “Can I make this happen by myself? If not, can I make it happen with a 1-3 people I know and can work with?” If the answer is “No”, then it’s probably time to toss the idea out or rework it until the answer is “Yes”. As I’ve gained experience and grown as a developer, the scope of ideas I can answer “Yes” to has steadily grown. I’ve also come to realize that a lot of my early ideas were stupid - they might have had some interesting aspects to them, but they were either too elaborate or just impossible to implement. Keep in mind that “make it happen” could mean “build a prototype to demonstrate the gameplay or principle at work”, not necessarily an entire finished product.Remember, ideas are only good if they can be made a reality.

Ideas are not special snowflakes that need to be nurtured and protected from the harsh realities of the world. Ideas are extremely common. You should always be ready to change or discard your ideas and come up with new ones - nothing is sacred. Ideas exist as potential solutions to a problem. If the idea cannot actually solve the problem, then you must discard them and move on to one that can or revise and fix your failed idea to make it work. To do this, you need to be able to evaluate your idea for feasibility. What are its possible failure points? What assumptions does the idea make? What happens if one or more of those assumptions is wrong?

Remember, pitching an idea is more than just getting someone to buy into the idea itself. Whenever you pitch an idea, what you are really pitching is your ability to make that idea a reality. Nobody is going to pay for someone else’s idea only to do all of the work themselves, not when they are fully capable of making their own ideas a reality. Which goes right back to my litmus test - if I can’t do it myself (or within a small team of people I actually know and can work with), then it’s not a feasible idea and I need to come up with something else that I can do. If you go into game development, you’ll often be asked to come up with ideas to solve problems. In those situations, coming up with an idea that doesn’t involve you solving the problem won’t fly. Any idea that actually gets used will almost certainly require you to make it happen. As your skills improve and you gain experience, the scope of ideas you can say “Yes” to, as well as your ability to determine an idea’s feasibility, will also increase.

[askagamedev]

What does a concept artist do during the the later half of a game's development (or near end), Do they start working on another project??

Sometimes! What a concept artist does during production often depends on the studio, the project, and the artist’s individual skills. The main issue is that a project really only needs so much visualization and concept work, and it’s usually done fairly early in the development process. Sometimes you’ll see some concept work done late to fill gaps and such, but that’s usually pretty rare - preproduction is the time to handle that sort of thing, in order to establish the visual style for asset creation during the production phase. After that’s done, the team leaders need to find other things for the concept artists to do - businesses can’t afford to keep paying salaries if no work is being done, but we also want to keep them if we can since hiring is expensive and good help is hard to find. So the team tries to find them work to do in some way, shape, or form.

As you theorized, large studios (i.e. a studio that has more than one project in development at a given time) will often shuffle the more senior concept artists onto new projects that are earlier in their development process. This is only possible at what is sometimes referred to as a “one and a half” project studio - a studio capable of handling one full project in production mode and a “half” a project in the concept/preproduction phase. But this doesn’t always happen either - sometimes the project schedules coincide or run into delays or whatever. When that happens the studio ends up with a hole in the schedule, in which case the orphaned concept artist will need to do something else to earn his or her paycheck. In the worst-case scenario, the concept artist might not have any other skills and is laid off. Sometimes studios will prepare for this by only contracting concept artists for a project and release them afterwards, rather than bring them on full time. 

Most of the time, the concept artist will be expected to pick up other art-related duties depending on what the artist is good at - character modeling, texturing, environment art, rigging, animations, and the like for the project development. Sometimes concept artists are loaned to the marketing team to produce or refine marketing material out of game assets/concept art for the game, or work on assets for DLC or cross-promotional products. This is also one thing that concept artist hopefuls should be cognizant of - a good concept artist will likely have some useful crossover skills aside from concept art, if only to be useful during time periods when concept art isn’t specifically necessary, but art assets still need creating. If you hope to be a concept artist, you have to realize that you’re going to be competing with people with those types of skills in addition to concept art.