AI: Difference between revisions

OK, we have positioning down; now for the actual behaviors that an AI can be set to execute within these ranges. There are fourteen possible combat behaviors (in brackets are the XML strings):

Combat ranges and various AI combat behavior was discussed in previous section. Even with combat ranges, there are still other parts of combat to be taken care of - picking up weapons from the ground, melee overrides of weapons, behavior if character is unarmed and of course, firing weapons or using hand to hand combat. Files inspected in this section will be [[CMBT]] profiles and [[ONCC]] files.

'''"Melee override" ([[CMBT]] profile)''' - similar to [[BSL]] command '''chr_dontaim''', this behavior bids the AI character to use hand to hand animation varient (see [[TRAM]]) and to switch from whatsoever other behavior to melee combat. This field was probably added to deal with conflicts when multiple AI behaviors are applied on character. Possible values are (xml strings in brackets):

:*None (None) - no override is used.

:*If Punched (IfPunched) - melee override applied when AI character is melee attacked by its enemy. Does not work when the character is invincible (cheat).

:*Cancelled - unfinished stuff, does nothing. Remains only the question what it was meant to be...

:*Short (ShortRange) - Melee override is applied when enemy is within Short range.

:*Medium (MediumRange) - Melee override is applied when enemy is within Medium or Short range.

:*Always melee (AlwaysMelee) - Melee override is applied withing all combat ranges

:*Alarm running - It is even required if alarm run is called via "If no gun" alarm run behavior, otherwise glitches will appear.

:*Retreating behavior - When "If no gun" is set as "Retreat", unarmed AI character will try to run away from its enemy. However, if enemy meets Melee override parameter (for example get into Short range while Melee overrride is set to ShortRange), then this AI stops running away and starts attacking the enemy.

:*Weapon firing - If distance between AI character and its enemy is smaller than minimal shooting distance, AI tries to run away from its enemy (still facing the enemy) till distance between characters is greater than minimal shooting distance. However, this backpedal behavior can be overriden by "Melee override" if all conditions are met - AI character then starts using melee (even with loaded weapon in hand) for at least 10 seconds (hardcoded timer) After ten seconds AI tries to restore its previous behavior. If enemy is still too close, Melee override is immediately applied again.  

:*Weapon pickup - if AI is trying to pick up a weapon and enemy crosses the range specified in MeleeOverride, then weapon pickup behavior is overridden by melee.

'''"If no gun" behavior ([[CMBT]] profile)''' - this parameter tells AI character what kind of action AI should do if it is unarmed or has empty weapon and no spare clips. Possibilites are (xml strings in brackets):

:*Melee (Melee) - AI character attacks enemy with hand to hand combat  

:*Retreat (Retreat) - AI character runs away from its enemy (a bit glitchy, but works)

:*Run For Alarm (RunForAlarm) - see section [[#Alarm behavior - "She's everywhere!"|Alarm behavior]]. Remainder: this alarm calling behavior requires Melee override set as ShortRange, MediumRange or AlwaysMelee, otherwise alarm behavior gets glitched and AI character gets stuck. If no alarm console is found within Alarm search distance, AI character resorts to melee.

[[File:GoForGun.JPG|thumb|right|alt=Picture showing AI moving to a weapon.|AI character moving to a weapon.]]

'''Weapon pickup behavior ([[ONCC]] file)''' - when in combat mode, unarmed AI character can be told to move to a loaded weapon and pick it up or to switch held empty gun for a loaded gun which is lying on the floor. Overall, AI characters only register pickable weapons which are lying around them up to a distance of 60 units (hardcoded). Weapons which are lying further than 60 units from the AI character are ignored. In [[ONCC]] file these parameters can be set to alter gun pickup behavior (xml tags in brackets ):

:*Chance for pickup (GoForGunChance) - percentual chance of AI being told to go and pick up a weapon. It seems that the weapon closest to the AI character is always chosen to be picked up.

:*Running pickup (RunPickupChance) - percentual chance of AI picking the weapon by performing an evasion move (melee dodge move).

'''Getting up after being knocked down ([[ONCC]] file)''' - if AI character is knocked to the ground, it stays on the ground for a while (simulation of concussion) then gets up. In [[ONCC]] file there are two parameters regarding getups (xml tags in brackets):

:*Knockdown minimal number of frames (DazedMinFrames) - minimal number of frames for which AI character stays on the ground.

:*Knockdown maximal number of frames (DazedmaxFrames) - maximal number of frames for which AI character stays on the ground.

:If knockdowned AI character gets hit by melee, it gets up immediately after the hit. Being hit by weapons does not make AI character instantly get up. Standard getups are simple ones (as if knockdowned player hit some direction key). If AI character is in melee combat mode, its MELE profile has getup attacks listed and enemy is within the required range, chance is this AI character will use getup attacks or instead of simple getups.

'''Making sure enemy is dead ([[ONCC]] file)''' - yes, even this is a part of Oni combat Artificial Intelligence.

:When enemy is defeated in hand to hand fighting, AI character stands for a while and "checks" if enemy is dead. During this interval AI character can utter a short victory speech if corresponding sound slot in [[ONCC]] is filled and percentual chance roll is successful. Also during "check body" time interval AI character can perform a taunt animation if percentual roll is successful. Here are listed all related fields from [[ONCC]] file (xml tags in brackets):

:*Investigate body (InvestigateBodyDelay) - time interval for which AI character stands next to its defeated enemy and stares at him.

:*Dead taunt chance (DeadTauntChance) - percentual chance of performing taunt animation.  

:*Check body sound probability (CheckBodyProbability) - Percentual chance of playing victory speech.

:*Check body sound (CheckBodySound) - link to Oni Ambient sound file ([[OBD:OSBD/OSAm]]).

:If the enemy is defeated by weapon, then AI character keeps shooting this dead enemy for some extra time to "make sure" the enemy is dead, then comes close to investigate the body. No taunts, no win phrases. Parameters of this behavior are:

:*Dead make sure (DeadMakeSureDelay) - time interval for which AI character keeps shooting the dead enemy

:*Investigate body (InvestigateBodyDelay) - it is the same as the one listed above.

Modding hints - behaviors enlisted in this section can be combined to achieve quite impressive results.

:*Unfortuantely, Oni does not provide (code-wise) any AI routines to deal with dynamic holstering and unholstering of possessed weapons. Thus, melee overrides are the only way how make armed AI character somehow defend itself when enemy gets too close.  

::Nevertheless, [[BSL]] provides function to make character holster or unholster a weapon - '''chr_forceholster'''. In order to make a character holster the held weapon, this character has to be using pistol or rifle animation variant (see [[TRAM]]). Since AI characters can use walk_noaim and run_noaim movmement modes (which disable weapon variant i.e. aiming with weapon), the weapon variant should be explicitly coerced via BSL function '''chr_dontaim'''. Unholster is easier, simply character has to be be executign some overlay-comaptible animation at the moment when chr_forceholster is executed. That means standing/running/crouching/walking/jumping is OK and function will succeed, but attack animations or animations of getting hit are not OK and function will fail.

::*IMPORTANT NOTE: The AI character must be "active" all the time in order to perform BSL animation checks ('''chr_wait_'''''animation/animtype/animstate'' checks). Remember that Oni was made back in years 2000/2001, so various tricks were used to save memory and enhance performance. One of these feints is making invisible characters (behind wall, behind closed doors etc) go into INACTIVE mode, which means they are only stored in a RAM memory as a structure, but no physics, no checks for collisions and no drawing functions are applied on them in order to save system resources (BTW yes, that means inactive characters can walk in air and pass through walls). On the contrary when character is ACTIVE, it is fully operational, physics working, collisions being checked and character being ready in graphics memory to be drawn anytime. To make sure character stays active means either applying individually "'''chr_lock_active''' ''ai_name''", or (since now is year 2011 ^_^) simply applying "'''chr_all_active=1'''" to make all characters be ready to be drawn anytime.

::Here is a simple example of a BSL scripted holster behavior. Character is given a gun, then weapon is holstered. When this AI character notices enemy and plays startle animation, then unholster is called. [http://www.youtube.com/watch?v=2WNMh8u5wBI THIS YouTube video] shows the script in action.

:*Melee override can be used together with "Go For Gun" behavior and properly sized Short combat range to create AI characters who jump the gun each time they have a chance yet they are not allowing enemy to land free hits in the process (If enemy gets too close, Short range melee override kicks in).

:*"If No Gun" behavior "Retreat" works in a rather simple manner - if unarmed, AI character is given a desire to run as far away from the enemy as possible. This behavior can look a bit awkward, but is useful for making more life-like civilians. Combined with Melee override at "short range" or "if punched" and a bit of BSL scripting to deliberately switch between "combatant" and "non-combatant", a modder can achieve impressive yet lightweight (on game engine) results. [http://www.youtube.com/watch?v=BTGQTAoU_1E See this YouTube video.]

:*Setting short getup times is a good way to make AI driven character formidable opponent in hand to hand combat. However, too short getup times can introduce problems. It is a good idea to experiment with getup parameters till the character feels "natural".

:* Don't overextend "Check body" and "Dead make sure" timers. It looks silly and on top of that it makes AI characters easy targets of a surprise rear throw.

:AI parameters regarding gunfire dodging are set in [[ONCC]] (xml tags in brackets):

:For each one of these weapons, there are in ONCC defined these parameters (xml tag in brackets):

:[[ONCC]] parameters for targeting and prediction (xml tags in brackets):

:[[ONWC]] parameters for targeting and prediction (xml tags in brackets):

'''Miscellaneous [[ONWC]] AI setup''' - there are a few more parameters in ONWC which affect AI behavior with the weapon. They are (xml tags in brackets):

:*basic parameters of a weapon (pistol or rifle type, type of ammunition etc.) can be set as a various flags in [[ONWC]] flags field (<Flags> in xml). These three flags from them affect AI behavior (xml tags in brackets):

:[[MELE]] profile always contains these parameters (xml tags in brackets):