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The AI Systems of "Left 4 Dead" [pdf]

valvesoftware.com

41–50 of 84 posts

Re: The AI Systems of "Left 4 Dead" [pdf]

#41
post #34
post #31

Earlier quoted context omitted.

The link is to the original. The scribd link is to the side and is automatically added by HN. (I never really liked scribd and with pdf.js it's clearly obsolete)

For PDFs at least, scribd seems purely parasitic.

I believe the intention of having the scribd links is to mirror the content if the original source goes down under the HN reader load, which has happened at times.

Re: The AI Systems of "Left 4 Dead" [pdf]

#42
post #17

That's hardly AI. It's just algorithms. Parametrized, using a probability distribution to randomize the environment, user programmed algorithms. EDIT: Well, if this AI in game development, then so be it. But it's still not AI in the generic way, IMHO. To downvoters: I didn't contest the fact that they don't work. I do enjoy this games a lot and I praise the programmers that make such games work.

That's what "AI" usually means in the context of game development.

Exactly, AI in games solves a different problem than "traditional" AI. It's merely about creating the illusion of intelligence. Not unlike what happens in rigid body dynamics (approximated, not actual physics sim), graphics (plenty of tricks here, e.g. displacement maps vs actual geometry), animation (e.g. blending canned animations).

Re: The AI Systems of "Left 4 Dead" [pdf]

#43
post #26

Earlier quoted context omitted.

That's what "AI" usually means in the context of game development.

Thanks, I edited my comment. I am more in the field of general AI ( and the rest of pure definition of AI ). So normally what I saw is the intelligence of a programmer put into very clever algorithms. I don't see any learning effect , or persistence effect. In fact, once you shut down the game, it starts all over. I'd love a game that learns from the player ( like how to climb over an obstacle ). Or can anyone point…

If a system can learn, isn't that Machine Learning (which itself is a subfield of AI)?

Searching algorithms have always been part of the AI field.

Re: The AI Systems of "Left 4 Dead" [pdf]

#44
post #41
post #34

Earlier quoted context omitted.

For PDFs at least, scribd seems purely parasitic.

I believe the intention of having the scribd links is to mirror the content if the original source goes down under the HN reader load, which has happened at times.

IME, HN readers will almost always post either a Google cache link or cache the original content. The scribd thing just slows everybody down.

Re: The AI Systems of "Left 4 Dead" [pdf]

#45
post #9

Question about the navigation mesh. I'm assuming that represents an entire open area (otherwise the path optimization makes no sense) and the dark stuff are the obstacles. In that case I'm wondering how the arrive at the actual grids and arrows (slide 12)

Yes, navigation meshes can be created either automatically, by a designer, or through a mixture of the 2 (usually they are first computed and then adjusted by someone). Indeed, automatic and stable generation is essential in case of big, procedurally generated scenes, and it would be in general a nice achievement for the field. gmaslov provided links that explain some common ways of generating navigation meshes, that quickly looked to me like improved/refined application of the "flood filling" method. I just wanted to point out that there is a very interesting way (imho) of generating a 2D/multilayered navigation mesh, which is, by computing the Generalized Voronoi Diagram of the obstacles and then by annotating the vertices (and thus edges) of the graph with information about the closest obstacles' points. This way, we have both a "backbone graph" and a subdivision (a mesh). Here is a link to the related research of my Uni: http://www.staff.science.uu.nl/~gerae101/motion_planning/ecm... check it out if you are interested, there are also a couple of summarizing images and videos. The advantage is that such meshes are smoother, compact, yet they ensure very good coverage of the walkable space.

Disclaimer: I am a MSc student working on the above method for my final thesis (involving GPGPU steps and a true multi-tiled approach).

Re: The AI Systems of "Left 4 Dead" [pdf]

#46
post #41
post #34

Earlier quoted context omitted.

For PDFs at least, scribd seems purely parasitic.

I believe the intention of having the scribd links is to mirror the content if the original source goes down under the HN reader load, which has happened at times.

Or, the intention of having Scribd links is to boost SEO for and awareness of Scribd, thus increasing the value of Y Combinator's equity stake.

Re: The AI Systems of "Left 4 Dead" [pdf]

#47

Earlier quoted context omitted.

That's what "AI" usually means in the context of game development.

Exactly, AI in games solves a different problem than "traditional" AI. It's merely about creating the illusion of intelligence. Not unlike what happens in rigid body dynamics (approximated, not actual physics sim), graphics (plenty of tricks here, e.g. displacement maps vs actual geometry), animation (e.g. blending canned animations).

One could argue that "traditional" AI is also about creating the "illusion" of intelligence. That is what the Turing test is testing -- whether the illusion is sufficiently good to fool the tester into thinking that they're communicating with something intelligent.

The difference is in the degree to which the illusion has to hold up. Game "AI" exist in a limited, artificial world; so they can get away with "simple" algorithms without any learning elements. General AI needs to operate in the real world (even if constrained to a particular domain), where the "rules" are too numerous and complex to program in advance; thus learning is an essential part of "traditional" AI.

Re: The AI Systems of "Left 4 Dead" [pdf]

#48
in the past few months i started to learn a little bit about AI, including algorithms in planning (like PDDL) and logic engines. the more i learned the more i saw what the gaming companies, and that entire community, are doing and how they are some of the biggest consumers of these technologies. i have to say that it's impressed me, and it seems like the gaming companies are on the forefront of multiple areas of technologies, not just graphics and specialized CPUs.

no if only i could hire from that talent pool :)

Re: The AI Systems of "Left 4 Dead" [pdf]

#49
post #24
post #10

Earlier quoted context omitted.

I always wished that I could tell the bot teammates "stick together", "fan out" or "help me" via the chat. That would give them an actual sense of social intelligence, and bring them closer to real players (to be 100% realistic they would then have to ask "where r u??" :)).

Oh man that would be so cool. I suppose if text based adventure games can "understand" meaning within text, there's no reason it couldn't be remodelled into a chat setting.

There are plenty of FPS games with AI that you can control with commands. The Rainbow Six games all have this, and if I'm not mistaken, I believe Counter Strike's bots can be controlled with commands as well.

Re: The AI Systems of "Left 4 Dead" [pdf]

#50
post #26

Earlier quoted context omitted.

Thanks, I edited my comment. I am more in the field of general AI ( and the rest of pure definition of AI ). So normally what I saw is the intelligence of a programmer put into very clever algorithms. I don't see any learning effect , or persistence effect. In fact, once you shut down the game, it starts all over. I'd love a game that learns from the player ( like how to climb over an obstacle ). Or can anyone point…

IIRC, there was a survival horror game that claimed to learn from and adapt to the player in order to provide a scarier experience (playing to the player's phobias and such). Not sure if that qualifies.

F.E.A.R.'s AI was supposed to work this way, I do believe.

http://web.media.mit.edu/~jorkin/gdc2006_orkin_jeff_fear.pdf

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