Urban area's ... obsticles

[Clees]

My idea...

The problem with AI in urban combat it that it dose not understand enviroment (its becouse lack of functions which could give you infromation how close it is to the nearest wall etc. - this information could be very, very useful for skilled scripter).

The solution for it can be found - but its quite ... "simple" and a bit "physic".

We have function to create objects. createCamera (or whatever)
We have function to set postion of a object
We have function to get a pice of information of objects current (very importent in my idea) position
And moust importent : we have funtions to set some objects velocity (if im wrong - tell me - but I think yes)

1. We create a object which dose not fall on ground when dropped (zero mass or in other words error in programming )
2. We set position of it very, very near our soldier.
3. We setVelocity of this object in any wanted direction
4. In short periods of time we check position of our "thrown" object.
5. When this object stops (its position dose not change so fast as some time ago) (I hope it stop... dont know ... It should be ... you know) it means - we have an obsticle ... we have its location... we can do with this information whatever we want...

what do you think?

[HotShotAce]

umm, basically i didnt understand anything in this post but i do understabd you want AI to move through an urban enviroment right?

this might help :

http://www.ofpec.com/yabbse/index.php?board=27;action=display;threadid=20876

[Triggerhappy]

i understand that, could be a very useful function
great idea!

[Clees]

Ok... two days ago I wrote simple script to check this idea: here are my observations:

1. We can change velocity only of object of class vehicle which have engine (it's not possible to throw for example a chair - and im not taking here about calculating new position and changing it place by place by setPos - try playcing a object chair named chair1 , a trigger and give in activation chair1 setVelocity [1,0,0] - nothing will happen).

Conclusion :

This script requires a new addon - an invisible (and visible req. during debugging) object of class "vehicle" on which function "setVelocity" can be executed with effect.

[XCess]

Sounds like sonar to me. Wouldn't it be easier to use objects IDs and getPos?

[Fragorl]

Clees:

What you are talking about is a trace, right? You have a starting position and an endpoint, and you move an item along this path until it hits something or reaches the end. This is common programming practice, at least in the Uneal series which i can speak for.

I tried implementing this in a function in ofp using a modified bullet that did no dammage as the trace object. The problem I found was as the function is instantaneous you cant have any delays, and what ever item you want to do the trace with doesn't have time to move along the trace path, before the function finishes. You could try using a script but that would defeat the purpose of an instant function.

I agree, it would be very useful if someone could get it to work! I made a couple of functions to work around this, but they aren't as good as this would be. Be cool if someone could get it to work tho.

[HotShotAce]

What I'm trying to understand is what this script will actually do? Can someone explain it to me please. From what I understand its for AI movement in urban areas. Will it be like the urban ai script recently released where your men go to your last position or will your men constantly follow you like in games like full spectrum warrior?

[Clees]

To HotShotAce

Not only AI movement in urban areas. This kind of function could return position of real obsicle - very, very useful information. What I mean by this?

Example : In editor You place a house on position [x0,y0,z0]. House is a quite large object (walls, etc.) and takes some space on ground. There is no inprogrammed function which could return you position of single point on the wall of a house (exa. [x0 - 20, y0 - 11, z0]) (a tank, a big box or anything else behind you can hide (you can do it without programming - I hope ;-) - AI cant)

"Will it be like the urban ai script recently ..."

If someone could write script in which this kind of function would be used (to gather information about real enviroment) results would be very, very impressive.

To Fragorl

Yes. I think its called ray-tracing. Yhe, its very common (to be honest Im quite sure it has to be implemented to OFP AI sorce-code - but we dont have access to it ... nevermind).

"... to move along the trace path, before the function finishes ..."

And what about function which execute itself till (it could "kill" cpu) condition is met (for example.. trace velocity more/less zero or else.. better) and then returns its position.

[Fragorl]

@Clees

You're right, there will be something like this in the native ofp code. For instance i think that's how the ai manages urban navigation in actual island towns, and how they keep formation, and how they check for line of sight to other players etc.

What you are talking about is a trace, right? You have a starting position and an endpoint, and you move an item along this path until it hits something or reaches the end.

Actually, this isn't quite right. There is not necessarily any object involved, its more just a mathematical collision check between the trace's position and any overlapping objects.

With any luck since 1.96 is the last(?) patch, Bis will open source at least some of their code, or provide a detailed editor or something. We can only hope.

I don't know about deliberately hijacking cpu time to focus only on your function, but i do know that this pretty much happens anyway if your function loops with 'do...while' whilst waiting for an object to be destroyed or disappear... a really noticeable drop in fps...
 
i made a couple of line-of-sight functions to get by this which were purely mathematical. They checked if an ai soldier could 'see' another soldier or object, but the problem was they had to treat ALL in game objects as 1.) the same size, and 2.) as simple geometric objects, i.e a rectangular prism.

[HotShotAce]

i understand now... simple but effective, hope you can pull it off, thnx for explaining (btw, recent urban script is nothin like this, just positions on map.)

[Triggerhappy]

this sounds really cool, so I'm workin on it for now.

no promises though!  

[Sentinel]

I came up with an idea of listing dimensions of most common houses (are there that many house types  ) and use that as a database. Then it would be needed to define ai that those areas where the houses are, aren't passable (or a point to move).

[Triggerhappy]

the idea i had was using OFPs clipping problems to find objects

sending 8 invisible things out a 45 degree intervals and move em out until the move i set them at isn't where they are.

using while..do to loop it and getpos/setpos to move the object outward

[Fragorl]

@Sentinel
I might be able to incorporate the house sizes into my function(s) perhaps, if you gave me the dimensions relative to the direction of the house

@Triggerhappy
Did it work?

[Triggerhappy]

haven't finished it yet, i haven't found anything that will clip (i tried sticking a gamelogic in a building and used hint format to tell the pos and it didn't move)

i suppose a bullet would work, but i'm not sure how to camcreate one

[Seabiscuit]

A bullet would damage what it runs into wouldnt it?
What about using the invisible H or invisible targets?
And will this really work?
Triggerhappy, you mentioned the clipping problem.
I've noticed many times that AI will just walk through walls when I place them inside a building and give them a move command.
And using a setpos I can set units in the middle of a wall or halfway between a floor without affecting them at all.

It would seem to me that as far as groups and formations are concerned, units need only to determine where their next highest ranking member and perhaps next subbordinate are, not every member of the group, therefore they only track the position of 2 objects.
This would be a simple binary tree one person/branch on the tree dies and the leaves fill in(too many programming analogies?).
As for all the other objects, AI seems to be mostly oblivious to them in their natural state except that they cant walk through most of it(exception above).
When you place a group and tell them to attack they dont care what's in the way, tree or house, they move toward it.
If the group is in formation, they hold that formation even if units end up in the water or outside a building or whatever.
In fact the AI can see right through objects right? (not sure if this is true for buildings but certainly for trees and shrubbery)
They take little consideration to windows or doors when inside a building shooting out and wont bother hiding (the best they can do is lay down and stay in formation).

Not trying to bring the ideadown , just thinking out loud.
I really hope this works out cause it would be like having a nearestNonClippingObject function in addition to nearestObject.

[Fragorl]

Yes, that is exactly the point. The AI's use of cover is abysmal, because the ai has no concept of 'cover' as it applies to shrubbery, houses, trees etc.
The point of the function would be to allow the ai to at least have some concept of not being able to 'see' another player, and either use this to their advantage (cover) or get around it as a problem (hunting a player)

edit: anyhow, here is my old workaround for the lineofsight problem. Uses projection vectors and such. Cheers to Machoman, i used his vector funcs

[Fragorl]

And after thinking about it for a while, i have another possible solution. It's more complex than just using a function, and has some undesirable aspects, but it is quite usable.

If we're using a bullet to do the line of sight check, and requiring it to move with a certain velocity, then there'll have to be a looping/checking aspect, which means a script. So think of this as sort of a latent function. There is a gap between when you start the trace and when you get the results of the trace (if and where an obsticle was encountered), but if you're prepared to have a short wait in your ai script or whatever (the length of the wait depends on how far you want to do the trace), then there is no reason this shouldn't work.

EDIT June 3 2005
Script posted here originally is out of date. New version will be completed soon