i have a new kind of AI behavior i want, that i've never needed before:

"do normal AI, while avoiding an area"

the specific case is doing normal predator or non-predator animal AI in Caveman 3.0 while staying away from campfires.

i discovered that "campfire nearby" and "taking missile fire" are not mutually exclusive conditions, and therefore require separate AI variables to avoid conflicts. so a change to the "flee from campfire" code is called for.

off the top of my head, it would seem that after deciding on a "move" the AI would have to then check to see if that "move" would place it near a campfire. if so, it would have to choose something else to do.

but the more possible "moves" the AI has, the more checks are required. skyrim has one type of AI (hostile) with two basic moves: attack and flee. caveman has at least a few more than that - perhaps as many as six different possible moves each for about six different types of AI. it would be a whole lot nicer if i could do one check in one place, rather than 36 checks in 36 places.

simply having an animal flee if withing 50 of a fire results in the critter oscillating between flee and close at a range of 50 feet, assuming their target is near the fire.

using a flag or state variable to flee at 50 and stop fleeing at 75 (or whatever) results in oscillations back and forth at ranges of 50 and 75 feet.

is one check per possible move the best approach, or should i go to a lower level and prevent targeting of entities near campfires altogether, or something else? is a separate AI state for "i can approach no closer" behavior required?

as i said, i've never had to write "avoid area" behavior AI code before - flee from area, yes. but avoid area while doing other stuff - no. so whats the easiest way to do this?

i want to keep it as simple as possible.

EDIT:

simply ignoring targets near a fire won't necessarily work. if the target is not near a fire, and the critter should flee from the target, away from the target might be towards a fire.

I have been using a modular influence map system at my last 3 clients (SOE for EQNext, ArenaNet for GuildWars 2, and now Pixelmage on Hero's Song). I wrote an article about it in the book Game AI Pro 2 and will be speaking about it at next year's GDC AI Summit.

The short version is that you project influence from things out into the world by propagating it into a grid -- falling off in value the further you are from something. When characters decide when to move, pick locations to move to, or even pathfind to new locations, they can look up values from the influence map system. They can determine things like "how much threat am I under right here?", "where is a low threat spot nearby?", or "what is a path I can take that has the least amount of threat?" By having different maps for different factions or hazards, you can combine them in meaningful ways to get a total value.

>> modular influence map system

nice!

influence maps - got it.

>> ArenaNet for GuildWars 2,

i saw the video (that was guild wars right?) good stuff.

thanks for the info.

BTW: what appended to the "selected quote" button on the website?

i may have just thought of a simpler approach.

the effect of an influence map would be to basically mark the area around a campfire as "impassable".

so why not just make the campfire a special kind of collide-able object with a really big radius? the effect would be the same.

this would be somewhat akin to embedding the influence data in the standard terrain collision map. so the collision map becomes the influence map.

its really not that different - add the influences to a copy of the collision map instead of adding collision data and influences to a separate influence map. the resulting map is more or less the same. so it still an influence map.

You know how in a movie, some people might get surrounded by fire and then they realize that the only way to get out of the situation is to dash through the least fiery area? That's what happens when you have degrees of danger.

Predators often have their own predators, and prey of course do

SO most active animals will have things they will seek (their goals) and others (like their predators) avoid. So such behavior decisions will be common to many of your animals/intelligent objects

Campfires and the humans around them would be classifies as a threat (to some) and be rated with some threshold sensor range and threat magnitude relevant to the beasty who is concerned/sensitive about this and checking for cues

You might be able to do a consolidated/shared 'influence map' for large numbers of certain beasties (for certain different 'threats' types). The granularity can be cruder (bigger grid squares) depending on how accurate it needs to be.

and if required do partial rebuild (or update) sections of it on an interval (round robin to spread it out if its alot of processing).

It may not change that fast - or it might be allowable to have the changes/revisions be driven/forced by movement activity to accelerate particularly active sections/areas of the mapping when needed.

Something like that (a basic influence map check) might also simply be a filter for early culling, leaving the objects who would run more costly/accurate processing to drive their behavior.