AI: Difference between revisions

[[File:Pathfinding grid.JPG|thumb|right|alt=Example of a pathfinding grid.|An example of a pathfinding grid.]]

[[File:Ai2 showastar2.png|thumb|right|alt=Example of an A*.|An example of the A* algorithm's work: nodes chosen as a path for AI are highlighted.]]

:*alarm running - AI character is requested to go to given console and use it, see section [[#Alarm behavior - "She's everywhere!"|Alarm behavior]]

:*pursuit of target - AI character loses direct sight of the enemy, see section [[#Pursuit of enemy alias "I will find you..."|Pursuit of enemy]]

:*running to weapons in order to pick them up, see [[#Combat behavior part 2|Combat behavior part 2]]

[[File:VisionFields.JPG|thumb|right|alt=Visualization of vision fields.|An example of a blue Striker's central and peripheral vision.]]

[[File:SoundSpheres.JPG|thumb|right|alt=Visualization of sound spheres.|Three examples of sound spheres.]]

 

Modding hints - the parameters of the vision fields are stored in ONCC, under '''<VisionConstants>'''. The central vision field distance has to be greater than the peripheral vision field distance, otherwise peripheral vision detection will somehow be broken (it will not detect). Since peripheral vision makes the AI pursue the enemy but not attack it, it can be set quite large in order to surprise lousy stealth players. But be warned: nobody likes cheating AI ^_^.

:Another example is a workaround for AIs to get alerted by dead bodies:

::Set the death particle in the ONCC to emit a custom impact effect. That impact effect will have no sound or effect attached, but will be set to be heard by AIs as gunfire within a large radius (say, 200 units).

 

:*Minimal: the minimal alert level this AI can have

:Watch [http://www.youtube.com/watch?v=OMFK5iKcZ5Q this YouTube video]. Pursuit mode is quite buggy, so when setting pursuit behaviors, there are several important things a modder has to have in mind.

::[http://www.youtube.com/watch?v=jnsGuZxqW9I Watch this YouTube video.]

:*In extreme cases, an AI can be even made to move through the level on it own, from one console to another. That can be used to create "chase" missions -- an AI wants to activate a certain number of consoles, while the player is required to stop it from doing so. Thanks to Alarm behaviors, the task of tripping consoles can be fully completed by the AI, no scripting needed. Such a setup is on the one hand prone to possible AI glitches, but on the other hand can add an element of randomness and increase replayability.

 

 

[[File:combatRanges.PNG|thumb|right|alt=Example of combat ranges.|Combat ranges of an AI character.]]

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):

:*Mutant Muro melee (MutantMuroMelee): the AI is only allowed to melee, not fire weapons. This behavior places "chenille" (the overpower effect) on the user. In order to see this visual effect, the character has to have <HasDaodanPowers> set to 1 in their [[ONCC]]. This chenille mode does not grant the actual damage overpower effect. If the ONCC has both <HasDaodanPowers> and <HasSuperShield> set to 1, the chenille mode called by this behavior grants "super shield".

::Chenille mode lasts forever if it is not terminated either via BSL or by the AI performing a TRAM which has a DisableShield flag. After a 10-second interval, chenille is turned back on. Another specialty of this behavior is an automatic backward-evasion move when about 35 points of damage or a throw are inflicted on the AI. Chenille mode is turned off if this AI switches to some other combat behavior because the enemy moved to some other combat range.

:*Superninja's behaviors sound excellent for cunning enemy units, however the annoying check for a character's minimal allowed height from the world origin, and subsequent forced re-positioning, severely impact these behaviors' usefulness. With a level which is deliberately raised to the correct height, the behavior will not cause random AI character re-positioning. Then it can be used to its fullest.

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.

==Combat behavior part 3: "They see me shootin', they hatin'..."==

Back in 2001 Oni was highly praised for its mixture of shooting and hand to hand combat. Now what could AI designers of Oni possibly do to make AI characters aim, pull a trigger or to make them avoid being hit by enemy? In this section, [[ONWC]], together with [[ONCC]] and [[PAR3]] will tell the story.

:First let's look into [[ONCC]] file. In XML file, under <AIConstants>, there's a tag named <Flags>. In binary file it is a bitset, so more than one flag can be written into it. XML strings for flags are:

:*noStartleAnim - Disables startle animation when AI sees the enemy for the first time.

:*EnableMeleeDodge - Enables firingspread/projectile dodging when AI is in pathfinding mode or combat melee mode

:*RunAwayDodge - Enables firingspread/projectile dodging even when AI itself is shooting a gun. AI character stops shooting and tries to move away from the danger area.  

:*ShootDodge -  Enables firingspread/projectile dodging even when AI itself is shooting a gun. AI character keeps shooting its enemy while at the same time attempts to move away from the danger area.  

:*NotUsed - Some ONCC character have this bit set, however it looks like it does nothing.

[[File:Firingspread.PNG|thumb|right|alt=Example of a firingspread.|Example of a firingspread.]]

[[File:Projectile.PNG|thumb|right|alt=Example of a particle with AI projectile dodge radius.|Example of a projectile with AI dodge radius (blue sphere).]]

'''Gunfire dodging mechanics'''. Gunfire dodging mechanics is a quite interesting part of Oni AI system. Interesting because the retail version features little to no such a behavior displayed which is sad because it gives a feeling of challenge to a gunplay. In order to make AI character perform dodge mechanics, this AI must be in combat mode with some enemy. Without combat mode and some enemy, AI character won't dodge. Next, AI characters perform dodge when the character intersects with:

:*Firingspread - can be seen by '''ai2_showfiringspreads=1'''. Firing spread is an invisible prism (dimensions set in [[ONWC]]) which can be created when a weapon is fired. Not every gun has a firingspread as for some guns firingspread is useless (SCRAM cannon, SuperBall gun). If AI character can dodge gunfire and intersects with a firingspread, this AI character starts gunfire dodging mechanics.

:*Projectile - epic win of Oni modders, can be seen with '''ai2_showprojectiles=1'''. In retail version of Oni, projectile dodging '''is defunct''' due to a couple of bugs in a projectile dodging code. Since the engine hackers/modders '''fixed this issue''', AI characters can execute gunfire dodge mechanics versus [[PAR3]] particle, if these AIs are in combat mode with some enemy and the particle has set <AIDodgeRadius> to a positive non-zero value.

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

:*Dodge reaction delay (DodgeReactFrames) - a delay in number of frames. This delay makes A.I character wait a bit inside danger zone before this AI character starts its reaction on firingspred/projectile.

:*Dodge timescale (DodgeTimeScale) - how long should the AI character's gunfire dodge reaction last.

:*Dodge weight (DodgeWeightScale) - how strong is the desire (???length of vector???) of this AI character to dodge a gunfire. Dodge can add together with other "vector" movements and a sum of all vectors is the direction in which AI character will try to move.

:Parameters of firingspread in [[ONWC]] are (xml tags in brakets):

:*Firingspread length (FireSpreadLength)

:*Firingspread width (FireSpreadWidth)

:*Firingspread skew (FireSpreadSkew)

:Parameter of projectile dodging in particle system [[PAR3]] is AI dodge radius (AIDodgeRadius).

'''AI character's prowess with guns'''. Still in [[ONCC]], there are data how "skillful" this AI character should be with each weapon in the game. Weapons are indexed (starting from zero) as follows:

:*w0_sec (0) - Only Bungie West empl-yees know what this weapon was supposed to be.

:*w1_tap (1) - TCTF automatic pistol

:*w2_sap (2) - Syndicate sub-machine gun

:*w3_phr (3) - plasma rifle

:*w4_psm (4) - phase stream projector

:*w5_sbg (5) - grenade launcher alias SuperBall Gun

:*w6_vdg (6) - stun gun ('''V'''an '''D'''e '''G'''raaf gun)

:*w7_scc (7) - scram cannon (swarm of small homing rockets)

:*w8_mbo (8) - mercury bow

:*w9_scr (9) - screaming cannon

:*w10_sni (10) - Mukade's Devil star (annoying red ball) as a holdable weapon; probably a relic from game development  

:*w10_ba1 (11) - Barabas' gun

:*w11_ba2 (12) - Barabas' gun; this one cannot be shot and is probably just a development relic.

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

:*Recoil compensation (RecoilCompensation) - How much the AI cahracter compensates the recoil of the weapon. Setting this to 0.0 mean no compensation, setting this to 1.0 means full compensation.

:*Best aiming angle (BestAimingAngle) - In radians, but question is whether it really affects aiming.

:*Shoot group error (ShotGroupError) - Random deviation of AI's aim within the target spot. Incorporated to simulate human inaccuracy. Can be set more than 1.0.  

:*Shoot droup decay (ShotGroupDecay) - Random deviation of the target spot. Target spot is always loosely based on enemy's position. Can be set more than 1.0.

:*Shooting inaccuracy multiplier (ShootingInaccuracyMultiplier) - How much can AI stray with its aim from the target. Not clear how much it really affects aiming.

:*Minimal shooting delay (MinShotDelay) - Minimal pause between reload and the beginning of a gunfire for this AI character.

:*Maximal hooting delay (MaxShotDelay)- Minimal pause between reload and the beginning of a gunfire for this AI character.

'''Targeting and prediction''' of enemy's movement. Apart from majority of other games, Oni AI does not "cheat" by being 100% accurate and then having some kind of additive error (even tough additive error is present in Oni, see above). It is a bit inverse - there's a bit of a problem making AI being a reasonably precise marksman ^_^. AI character is given input parameters such as distance between characters, present velocity of its enemy (vector) and velocity of held gun's projectile (number, not a vector). From this data, AI logic computes a prediction of enemy's location and ideal aiming direction in order to hit the enemy.

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

:*Predict amount (PredictAmount)- Some sort of multiplier for prediction mechanics.  

:*Predict position delay (PredictPositionDelay) - In frames, delay before prediction is applied, so AI characters always uses a bit outdated prediction result.

:*Predict delay frames (PredictDelayFrames) - In frames, delay before prediction is computed. Must be set at least to 1.0.

:*Predict velocity frames (PredictVelocityFrames) - Number of frames interval but meaning not 100% sure. Maybe enemy's velocity data are obtained and used for prediction algorithm during the interval? Must be set at least to 2.0.

:*Predict trend frames (PredictTrendFrames) - Number of frames interval but meaning not 100% sure. Maybe a trend (sort of extrapolation of enemy's movement) is computed with data from this interval? Must be set at least to 2.0.

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

:*Prediction speed (PredictionSpeed) - More precisely "projectile prediction speed". This value is taken by prediction algorithm as a speed of a projectile fired with the corresponding fire mode of the [[ONWC]] weapon. Thus when actual [[PAR3]] projectile's speed is changed, prediction behavior produces misleading values (AI is unable to hit moving targets).

:*Maximal inaccuracy angle (MaxInaccuracyAngle) - Maximal allowed deviation of aim from the enemy's character pelvis in order to keep firing the weapon. If exceeded, AI ceases fire and corrects aiming, the resumes fire. Pelvis is taken as a root point of the character, so without any extra chages done to targeting origin and targeting vector (see [[ONWC]]) AI characters always target pelvis of the enemy.

:*Aim radius (AimRadius) - no idea what it does.

:*Ballistic projectile speed (ProjectileSpeed) - special prediction can be used if weapon is meant to fire relatively slow but gravity affected projectiles (grenades). AI then adjusts aiming in order to hit enemy with the projectile according to the ideal (parabolic) ballistic curve. This is a horizontal speed component.

:*Ballistic projectile gravity (ProjectileGravity) - vertical gravity attraction for the projectile.

:*Targeting direction (Direction) - Vector with three components (x, y, z) which gives orientation of a firingspread. When set to wrong values, firingspread will not cover area where the weapon shoots, but will be pointing in some other direction ( can even point backwards ^_^). Friendly advice: do not alter unless needed.

:*Targeting origin (Origin) - Vector with three components (x, y, z) which tells AI where to fire according to enemy's pelvis position. When armed AI is in combat mode with the enemy and shoots him, the AI searches for pelvis (see [[TRIA]]) as the pelvis is the only bone recognized by AI system. For AI, pelvis is a representation of a whole character. Now when AI fires at its enemy, the AI aims for pelvis. The vector described in this parameter tells AI where and how much to deviate from enemy's pelvis position.

::So when the vector is set as (0, 0, -2), AI will aim and fire at enemy's pelvis position + two units above. That means AI will fire ABOVE the pelvis position. Here is described effect of setting "x,y,z" from SHOOTER's point of view. First to positive, then to neative value:

::*x - deviate forward/backward (does not have much of an effect)

'''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):

:*Minimal shooting distance (MinShootingDistance) - defines how close can enemy be to the armed shooting AI character. If enemy comes closer than this distance, AI stops shooting and tends to move back a bit (vector type of movement, see [[#Pathfinding and movement|HERE]]) until the distance is again equal or greater than Minimal shooting distance. Then AI opens fire again. To witness the effect, see some AI operating an SBG when its enemy is close to it.

::'''IMPORTANT''' - for some unknown reason, value from this field is '''divided by 2'''. So when 100 is set, ingame AI starts backing when its enemy is 50 units close to it.

:*Maximal shooting distance (MaxShootingDistance) - contrary to the parameter described above, this limits how far can enemy be till the AI stops shooting and tends to come closer. See some AI character shooting with w2_sap at distant enemy.

:*Fight timer (FightTimer) - a bit similar to timer-based BSL command '''chr_dontaim'''. Defines in frames for how long should AI switch from a weapon varient (shooting) to a melee varient (hand to hand combat) if this firing mode was used (don't forget, weapon can has two firing modes) and certain conditions were met. See below for ''KnockdownSwitcher'' and ''StunSwitcher'' flags explanations.

:*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):

:**NoHolster - apart from holster disabled, this flag also makes AI character ignore this weapon on the ground. One exception is w10_ba1 when AI character has set Superammo flag (InfiniteAmmo in xml) in its [[CHAR]] profile, then this AI character can pick up WMC cannon. If AI character is given the weapon it will fire it, but if the weapon is lying on the ground and AI character does not have superammo flag, this AI character will never pick it up.

:**Stun switcher (StunSwitcher) - if the enemy is within armed AI character's shooting distance and was knockdowned, stunned or blownupped, the AI character switches to a melee for a time specified in the weapon's Fight timer (see above). The flag was designed specially for w6_vdg weapon.

:**Knockdown switcher (KnockdownSwitcher) - Similar to Stun switcher, but only knockdown or blownup makes AI switch to melee. Tailored for w4_psm, probably to avoid AI abuse of an unfair advantage the w4_psm weapon grants (enemy cannot get up as long as she/he is shot).

Modding hints: Phew, what a long section. Described material has plenty of modding possiblities. Still, modders should be aware of a few things:

:*Don't set too strong dodge vector (DodgeWeightScale) and don't overdo it with dodge timer (DodgeTimeScale, the smallest possible value is 0.4; lower is not registered). Delay before gunfire dodging (DodgeReactFrames) should be minimal, otherwise it can happen AI won't start dodging till shooter's weapon is empty.

::As a side note, there is a glitch in gunfire dodging. It is not a coding bug, but simple limitation of a "vector" type of movement. When AI starts gunfire dodge, it tries to get away from the source of danger (be it firingspread or projectile). And because vector movement works as a "desire" to go to some direction, it can happen AI will express a "desire" to go into wall. In such a case, character stops until the desire to move into a wall stops (in other words, until enemy stops shooting the AI character). When AI character is unarmed, she/he will try to switch between pathfinding movement (to go to enemy and attack him with melee) and vector projectile dodge movement, so it kind of looks like the AI still tries to dodge the gunfire. If weight of a gunfire dodge is set to be smaller than standard vector movement type weight, then AI even does not have to get stuck as it will run in zig-zag pattern towards the armed enemy.

::In case AI is armed with a loaded weapon, there is no point in AI running towards enemy. That means if the AI character starts dodging and meets a wall, this AI character gets "stuck" until enemy's gunfire stops. In case this character has set "ShootDodge" in [[ONCC]], it will at least fire back at the enemy shooter. But in case the character has set "RunAwayDodge", then it simply stands near the wall and stares and waits till enemy's gunfire ceases.

::From the text above it can be seen that gunfire dodge parameters should be set to make AI dodge but to not make dodge vector outweight the vector for moving towards the enemy.

:*AI's skills with weapons (in [[ONCC]]) can be used greatly to create sharpshooters or rookies who cannot hold a gun properly. For example by setting "ShootGroupError = 10.0" for w1_tap, we create a total amateur who's hand shakes all over the place when he fires Campbell equalizer.

:*Unless really needed, do NOT alter [[ONCC]] prediction parameters. Bungie set them quite reasonably and if they are messed, AI character loses the ability of prediction.

:*In [[ONWC]], Prediction speed is used for a calculation of AI's aim. The value should be exactly the same as the value of this weapon's projectile. Projectile's velocity is usually set in a emitter of a projectile particle ([[PAR3]]). That means Prediction speed and actual speed of a particle used as weapon's projectile may differ, the most significant case being w3_phr (plasma balls accelerate rapidly).

::If Prediction speed is set lower than the speed of a projectile is, AI will tend to shoot too much in front of the moving enemy since it will assume projectile is slower than it really is. On the other side, setting this value higher means AI will shoot more directly at the moving enemy (and probably miss) as the AI will assume projectiles are fast enough to hit the target.  

:*Similar to Prediction speed, there are Ballistic projectile speed and Ballistic projectile gravity. When these two are set non-zero, AI assumes ballistic projectiles (grenades) and tries to shoot projectiles according to an ideal parabole (the solution with shorter fly time is always chosen). In order to make AI sucesfully hit enemy's pelvis, these two must again corespond with [[PAR3]] particles's speed and particles's gravity attraction, but they can be used for modding purposes as well. For example if projectiles's gravity attaction is 0.5 but in [[ONWC]] Ballistic projectile gravity is set as 0.3, AI will shoot projectiles at enemy's feet as it will assume that gravity attraction of the projectile is lower thus it does not have to aim so high in order to hit the pelvis (credits to [[user:Gumby|Gumby]]). Remember: for AI system, pelvis is a representation of a whole character.

:*Targeting origin vector ([[ONWC]]) can be utilized to make AI fire not directly at pelvis, but for example higher (negative "z" component), so AI can score headshots. So far such a change does not have any purpose as characters don't have damage multipliers for bodyparts. But maybe in future...or with Paradox's headshot mod / material dependent damage mod ideas (see [[XML:BINA/ONIE#Extra_damage_for_head_hits|HERE]]).

:*One thing purposefully left out in main talk about weapons is that there is an option for AI chracters to make "startle" misses - when startled, AI fires at some random direction. Parameters for this behavior are in [[ONCC]] and [[ONWC]], but overall this feature is so subtle it does not need any special modding attention.

:*Remember: in [[ONWC]], Minimal shooting distance is '''divided by 2'''. Reason is unknown, maybe some bug in a code.

:*Through modification of Minimal shooting distance in conjunction with BSL scripting, a modder can achieve pseudo-dynamic holster behavior. If enemy gets too close, AI start moving away, facing the enemy. Since simply backing away is almost never used by armed AI (it usually move to the side), it can be detected via BSL function '''chr_wait_animation''' and subsequent script makes AI character holster held weapon. To unholster, different animation check has to be used, for example a check for a taunt animation. In [[MELE]], modder can set up approppriate melee profile which makes AI character taunt only at safe distance.  

::Drawback of this modification is is that enemy ''will not fire the weapon at point blank range'' and also it limits Melee override in [[CMBT]] to be only None or IfPunched, otherwise instead of backing away, AI character goes directly into melee.

==Combat behavior part 4 : "Everybody was kung fu fighting..."==

Ah yes. After all those OTHER things, we finally got to how AI system handles the core gameplay feature of this game, hand to hand combat.

First things first. As usual, player can see her/his enemy trying to perform some move, so player can then react. AI character cannot see a thing beacuse it does not have human eyes nor human brain. Thus the first question is how the AI knows about incoming attacks?

[[File:Melee zones.JPG|thumb|right|alt=Melee zones around a character|Rough idea of melee zones.]]

:Answer lies within [[TRAM]] files. Each animation which can hurt somebody should have EXTENTS. Extents are invisible marks which tell AI character how the attack's ''trajectory'' looks. There are two types, horizontal and vertical, but more important thing AI wise is that without extents attack TRAMs will not be registered by AI characters as attacks, so AI will not try to block them or dodge or attack with the [[TRAM]] animation properly. But if the attack has extents, then AI gets a complete knowledge of a whole path of attacking bodyparts of this enemy's attack (see attack part of [[TRAM]]).

:This info is used by melee part of AI for defense purposes (deciding what kind of dodge move to choose and whether to crouch or not) and for attack purposes - position move in melee techniques are used to give general info about the melee technique's positioning, but AI character will not execute the attack move of the technique till enemy is within chosen attack move's extent range.

:Also, for hand to hand purposes engine recognizes roughly four zones around a character, see picture on right. These zones are then corresponding with position moves, so when melee techique has for example CloseBack, then the only time this melee techique is listed for possible execution is when enemy is in the back of the AI character. In all other cases (enemy in left, right or front zone), this techique is NOT listed for use. Exception is a technique with GenerousDir flag, see below for more info.

Fistfighting AI mode is handled via [[MELE]] profiles. MELE profile is assigned to the spawnable character in its [[CHAR]] profile. When in melee mode, AI character uses vector type of movement. Unless specified otherwise, AI character is made to run towards its enemy.

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

:*Character class (CharacterClass) - Link to an [[ONCC]] class. Level of importance of this parameter not known, but maybe it is neccessary in order to allow for performance of some attack moves (engine checks referenced [[ONCC]] class and its [[TRAC]]).

:*Notice (Notice) - percentual chance that AI will register incoming attack. In retail profiles it is always set 100.

:*Dodge base (Base inside Dodge) - percentual chance AI will try to use one of '''evade''' moves (if it has any in evade section of MELE profile) to avoid getting hurt.

:*Dodge extra (Extra inside Dodge) - extra chance to dodge

:*Dodge extra damage (ExtraDamageThreshold inside Dodge) - amount of damage for activation of extra dodge

:*Single block skill - (Single inside BlockSkill) - percentual chance of attempt to block incoming enemy's attack

:*Group block skill - (Group inside BlockSkill) - percentual chance of ???. Not sure, maybe of blocking more attackers?

:*Not blocked (NotBlocked) - Multiplier which affects weight of techniques which will not be blocked by the enemy under current circuumstances (punch combo against opponent who is running forward).

:*Must change stance (MustChangeStance) - Multiplier which affects weight of techniques which force enemy to change stance (standing, crouching) in order to block it under current circuumstances (leg sweep against standing opponent).

:*Blocked but unblockable (BlockedButUnblockable) - Multiplier which affects weight of techniques that have "unblockable" flag in its attack part, see [[OBD:TRAM/raw0x14|TRAM-attack part]].

:*Blocked but has stagger (BlockedButHasStagger) - Multiplier which affects weight of techniques that makes enemy stagger if the enemy blocks the technique. Depends on TRAM attack part settings (BlockStagger), see [[OBD:TRAM/raw0x14|TRAM-attack part]].

:*Blocked but has blockstun (BlockedButHasBlockStun) - Multiplier which affects weight of techniques that lock enemy in a blocking animation for longer than 20 frames. Depends on TRAM attack part settings (BlockStun), see [[OBD:TRAM/raw0x14|TRAM-attack part]].  

:*Blocked (Blocked) - Multiplier which affects weight of techniques that will be certainly blocked by the enemy under current circuumstances and will not stagger nor stun the enemy.

:*Throw Danger (ThrowDanger) - Something with throws, but only Bungie West knows what's the meaning of this field.

:*DazedMinFrames, DazedMaxFrames - documented by Neo. Question is - do these two parameters actually have effect, since getup time is controlled from ONCC?

Basic melee setup is done. Now the profile branches into '''attack''' part, '''evade''' part and '''maneouver''' part. Each part has a certain number of "melee techniques". Melee technique is a compound of one or more melee moves. ''Melee move'' is a simple element of hand to hand combat - attack, throw, positioning command or some maneuver. Maximal amount of techniques in one melee profile is 32. If this limit is exceeded, Oni crashes. Let's have detailed look at all three mentioned parts of [[MELE]] profile:

:*Attack branch - Techniques from this branch are executed when AI is trying to attack and hurt it enemy. Attack branch contains not only attack techniques, but also maneuver techniques as well (more about this later).

:*Evade branch - Techniques contain moves which are used to evade attack. That means escape moves (SHIFT + some direction) and/or various jumps/slides. These techniques are picked only when AI character reacts on incoming enemy's attack.

:*Maneuver branch - Techniques from this branch should be used by AI to maneuver around, in order to move not only in a straightforward fashion towards the enemy, but also circle around, retreat or advance. Unfortunately, this branch is probably a development relic. In order to see these techniques performed, global [[BSL]] variable '''ai2_spacing_cookies''' has to be set zero (0). That means AI cannot execute attacks. Only then AI starts performing techniques from this maneuver branch.

::The idea was probably to make the AI execute a certain number of attacks (each attack "eats" a cookie), then make the AI maneuver a bit and so on and so on. But somehow this setup was abandoned (question is whether MELE was really planned that way ^_^ ) and techniques from this branch are de-facto never used. That means all maneouvring is done via Attack branch.

:*'''Name''' (debugging purposes only)

:*'''Flags''' - possibilities are:

::*Interruptible - This technique can "home" to some extent and if enemy gets away from its reach, technique is ended prematurely.

::*GenerousDir - This technique is enlisted for possible execution even when facing of the AI does not match position move of this technique (technique uses CloseLeft, enemy is directly in front). If technique is used, AI character positions itself in order to perform the techique (in our example case, AI chracter turns left side towards enemy and perform the technique).

::*Fearless - does this flag actually do something?

:*'''Weight''' - Basic weight of the technique. Techniques are chosen randomly but with "weight" of the technique taken into account. Techniques with higher "weight" are used more often than those with lower "weight".

::Also, there are more factors which affect final weight of the technique. ''Basic weight'' of the technique is according to combat situation (position of the enemy, effect of moves in the technique) multiplied by one of MELE profile setup multipliers (NotBlocked, BlockedButHasStagger etc.), then it is also multiplied by some dimnishing value which decreases weight of the technique if it is used consencutively. And finally, weight of the technique is multiplied by some special "orange tiles" mutiplier, which downweights techniques that would make the AI "fall over the edge", aka dive into orange tiled area.

:::The equation is PROBABLY very roughy something like this:

:::Final weight = Basic weight * corresponding MELE profile setup multiplier * dimnish multiplier * "orange tiles" multiplier

:*'''"Importance"''' - documented by Neo. Does it have any effect?

:*'''RepeatDelay''' - in frames, how long should be the technique unavailable after its use (to prevent from predictability). For this time the technique is not enlisted in a list of performable techniques.

:*'''Moves''', possible types of moves are:

::*Position - usually takes three parameters: minimal distance, maximal distance, tolerance range. Meaning of Minimal/Maximal distances is clear, tolerance range specifies extra distance (beyond chosen TRAM attack's extents) where AI chases the enemy till the enemy gets inside the extent range of the [[TRAM]] attack this AI charater wants to use. Then AI uses the TRAM attack ^_^.

:::Some position moves don't have any parameters (Crouch, StartToCrouch) and are used strictly for stance purposes - to make AI perform crouched or special attacks. Position moves are used to give the AI general sorting of available attacks, so based on the melee zone the enemy is in (see picture at the beginning of this section) only corresponding techniques are taken into account as "possible to be used" and the rest is ignored. [[OBD:BINA/OBJC/MELE/MoveList/Position|HERE is a list]] of all available position melee moves.

::*Attack - no parameter, simply some kind of attack action. [[OBD:BINA/OBJC/MELE/MoveList/Attack|HERE is a list]] of all available attack melee moves.

:::Attack move can be the only move of a techique (no position move). If that is the case, then this techique is put into a list of possibly used techniques only when its prerequisities (positioning and stance) are met via other means. For example Kick_forward can be used without a Position move, but then it is evaluated only when the AI character gets within the extent range of its Kick_forward [[TRAM]] move. Then the AI chracter has to somehow get into correct position within extent range of the Kick_forward's TRAM (maybe via other melee techniques), otherwise the technique with Kick_forward is labeled as MISSBOUNDS. When all that is OK, this a melee technique is listed for possible use.

::*Throw - no parameter, simply some throw. [[OBD:BINA/OBJC/MELE/MoveList/Throw|HERE is a list]] of all available throw melee moves. Again can be standalone, under circuumstances described above.

::*Evade - no parameter, simply some evasive action. [[OBD:BINA/OBJC/MELE/MoveList/Evade|HERE is a list]] of all available evasion melee moves.

::*Maneouver - up to three parameters, these moves are used to make AI character move around somehow (advance, retreat, circle left/right) or perform various movements (crouch, jump, taunt, use uncommon getup moves etc.) [[OBD:BINA/OBJC/MELE/MoveList/Attack|HERE is a list]] of all available maneuver melee moves. Almost all maneouver moves have a Duration ('''in seconds''') as a first parameter.

:In melee techniques there can be a mixture of melee moves. Very first move (shuold be position or maneouver) is evaluated to make sure if the technique can be performed under current positioning of the AI character and its enemy. However, throws and maneuvers are checked as well even if they are not the first tehnique, so if technique contains Throw_punch_behind, it will be listed for use only if the AI is in theback of its enemy. Surprisingly enough, pairing Kick_forward and Kick_back makes AI character kick forward when position is correct for kick forward move, then it kicks back even tough there is nothing to hit ^_^. Same with other directional attacks.

Also there is one special condition to executing melee techniques. When there is an edge of a platform nearby it is usually covered in pathfinding grid as a seires of special tiles from blue (border) to orange (danger). Engine seems to check if [[TRAM]] attack's extent extends into orange pathfinding tiles and according to it it decreases weight of such techniques which would make AI character end in orange field (i.e. going over the edge and falling down). Techniques which utilize jump position moves are excluded from weight decrease, so there is some very limited and random possibility for AI characters to jump aross gaps in order to reach the enemy.

:Code behind all this must be pretty complex, hands down before Oni developers who managed to pull this off.

:*Position moves can be followed by some certain other position moves, but generally after position move an attack or throw move is expected. If attack or throw is not present, this melee technique will be albeled as NOATTACKNOTHROW and will be unused.

 

 

:*Special attack (Rising fury, Devil spin kick) use StartToCrouch position move as a starter.

:*Any combo techique (for example three punch combo) without Interruptible flag makes AI character too vulnerable.

:*Rear throw techniques and side attack techniques should have high weight to ensure they will be chosen and used the moment there is a chance.

:*Set distances in position moves reasonably so AI character doesn't attempt to perform jump attack techniques or run attack techniques at close distance.

:*Always try to utilize given class's strength - Fury is fast, so upweight combos. Tanker is slower, upweight throws and run attacks. Ninja is a beast, set whatever you want and it will be annoying to deal with anyway.

<div style="text-align: center;">[http://www.youtube.com/watch?v=XeymFlbQuNg|'''THE END...''']</div>

[[Category:Modding information]]