Character Control Script
Contents
- 1 AI overview
- 2 Controller Script Interface
- 3 Goals
- 4 Sub Goals
- 4.1 Unknown Sub Goal
- 4.2 Provoke Attack Sub Goal
- 4.3 Avoid Jump Kick Sub Goal
- 4.4 Knock Off Ledge Sub Goal
- 4.5 Wait And Attack Sub Goal
- 4.6 Rush And Attack Sub Goal
- 4.7 Defend Sub Goal
- 4.8 Surround Target Sub Goal
- 4.9 Escape Surround Sub Goal
- 4.10 Investigate Slow Sub Goal
- 4.11 Investigate Urgent Sub Goal
- 4.12 Investigate Body Sub Goal
- 4.13 Investigate Around Sub Goal
- 4.14 Investigate Attack Sub Goal
AI overview
TODO: This page is a work in progress, and I intend to finish it sooner rather than later. I wanted to save my work to make sure it doesn't get lost
AI in Overgrowth is handled with character controllers.
A character controller is a set of responses to events/stimuli that tell the character what physically to do at a given instant in time. It's sort of like a cockpit for an airplane.
Everything a human can do is technically available to an AI implementation, if it's smart enough to figure out how to properly trigger the right action at the right time.
The AI in Overgrowth is implemented using a goal system, and through simulations of sensory input. It makes decisions on what to do at a given moment in time based on its current goal/subgoal, the character's current status, and observations on the environment (sights, sounds).
- For the player, this control happens in a script
Data/Scripts/playercontrol.as
- For NPCs, this control happens in a script
Data/Scripts/enemycontrol.as
There's a layer of logic below the character controller that dictates what the character is physically allowed to do. That logic triggers events and consequences based on what happens to the character, and listens to the inputs from the character controller to direct the character's motion. That layer won't be covered here in detail, though we will talk about the events and control queries that are sent from that layer into the character controller.
- For both players and NPCs this logic is shared, in a script
Data/Scripts/aschar.as
Controller Script Interface
The functions in this control script interface tell the character what to do. If you implement these functions, then you will control the character.
The rest of the details on this page just detail how we chose to drive these functions in the base character controller scripts. You can feel free to drive them in some other way as well.
Functions called from other scripts
These are called both directly (aschar.as) and via movement_object.Execute(...)
(by the engine, other scripts, and character-to-character calls)
-
bool ActiveBlocking();
-
bool ActiveDodging(int attacker_id);
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void AIEndAttack();
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void AIMovementObjectDeleted(int id);
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void BrainSpeciesUpdate();
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void ChooseAttack(bool front, string& out attack_str);
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bool DeflectWeapon();
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void DrawStealthDebug();
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vec3 GetDodgeDirection();
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string GetIdleOverride();
-
vec3 GetTargetJumpVelocity();
-
vec3 GetTargetVelocity();
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void HandleAIEvent(AIEvent event);
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int IsAggressive();
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int IsAggro();
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bool IsAware();
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int IsIdle();
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int IsPassive();
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int IsUnaware();
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void MindReceiveMessage(string msg);
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void ResetMind();
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void ResetWaypointTarget();
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void Startle();
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bool StuckToNavMesh();
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bool TargetedJump();
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void UpdateBrain(const Timestep &in ts);
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bool WantsReadyStance();
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bool WantsToAccelerateJump();
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bool WantsToAttack();
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bool WantsToCancelAnimation();
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bool WantsToCounterThrow();
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bool WantsToCrouch();
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bool WantsToDodge(const Timestep &in ts);
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bool WantsToDragBody();
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bool WantsToDropItem();
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bool WantsToFeint();
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bool WantsToFlip();
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bool WantsToFlipOffWall();
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bool WantsToGrabLedge();
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bool WantsToJump();
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bool WantsToJumpOffWall();
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bool WantsToPickUpItem();
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bool WantsToRoll();
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bool WantsToRollFromRagdoll();
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bool WantsToSheatheItem();
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bool WantsToStartActiveBlock(const Timestep &in ts);
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bool WantsToThroatCut();
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bool WantsToThrowEnemy();
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bool WantsToThrowItem();
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bool WantsToUnSheatheItem(int &out src);
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WalkDir WantsToWalkBackwards();
Data accessed from other scripts
These are accessed by aschar.as mostly. There's only one call to movement_object.Execute(...)
that modifies this data, in the older (no longer used) tutorial level.
Goals
The Goal is the current primary motivation for the AI.
Whenever the character is updated, this is consulted first when making decisions on what to do, before the Sub Goal is checked.
List of Goals:
- Patrol
- Attack
- Investigate
- Get Help (currently disabled - enable by editing the code to
bool kSeekHelpEnabled = true;
) - Escort
- Get Weapon
- Navigate
- Struggle
- Hold Still
- Flee
The inital Goal for all AI is Patrolling.
Patrol Goal
This patrol goal is when the character is on the alert, listening for sounds, looking for ally's bodies, and looking for awake enemies to fight.
The inital Goal for all AI is Patrolling, and this is the mode that they will fall back to when they're done in combat.
When Patrol gets set:
- When the character is first spawned
- When the character is reset (through the
void ResetMind();
function) - When the Goal was Attack and the chase target is neutralized, and there are no other targets to pick from
- When the Goal was Struggle or Hold Still and the character was broken free or was released, while still awake
- When debug keys are enabled, the
C
is toggled in the editor, the character was previously not passive, and the character is now being set to to passive, then they will also now be set to patrol - When
void MindReceiveMessage(string msg);
is called for the character, with the message "set_hostile false" (basically when this message is sent to the character withmovement_object.RecieveMessage("...")
) - When the Goal was Investigate
- If the Sub Goal was Investigate Slow, there was an investigate target position, and the character has now reached it (within 1 unit)
- If the Sub Goal was Investigate Around or Investigate Attack, and the Sub Goal was selected more than 10 seconds ago
- When the Goal was Get Help and somehow you no longer have an ally to seek help from (TODO: I don't think this was completely implemented, so it's not clear how this can happen without this goal being switched ahead of this check)
- When
void AIMovementObjectDeleted(int id);
is called, and the player had a goal that was focused on the now-deleted character:
How Patrol works: TODO: Write this section - or does this get delgated to sub-goals?
How character behaviors are affected by Patrol:
-
int IsUnaware();
returns 1. Other checks are also made, but this always returns 1 if on patrol -
int IsIdle();
returns 1, otherwise it returns 0 -
string GetIdleOverride();
returns a non-empty value only if the character is on patrol -
vec3 GetTargetVelocity();
returns waypoint based patrol movement if the character is on patrol, and isn't currently being startled -
WalkDir WantsToWalkBackwards();
returns WALK_BACKWARDS or STRAFE if the character is on patrol, they don't have a waypoint target, and they get pushed around. If they aren't on patrol, or they have a waypoint target, it returns FORWARDS -
bool WantsReadyStance();
returns true if the character is not on patrol
Attack Goal
TODO: Write this section
Investigate Goal
TODO: Write this section
Get Help Goal
TODO: Write this section
Escort Goal
TODO: Write this section
Get Weapon Goal
TODO: Write this section
TODO: Write this section
Struggle Goal
TODO: Write this section
Hold Still Goal
TODO: Write this section
Flee Goal
TODO: Write this section
Sub Goals
The Sub Goal is the current secondary motivation for the AI. Each goal has an entirely different set of sub-goals, and the sub-goals aren't really shared between goals. It isn't "a second goal", it is like a plan of action to solve the current goal.
Whenever the character is updated, this is consulted second when making decisions on what to do, after the current Goal is checked.
List of Sub Goals:
- Unknown
- Provoke Attack
- Avoid Jump Kick
- Knock Off Ledge
- Wait And Attack
- Rush And Attack
- Defend
- Surround Target
- Escape Surround
- Investigate Slow
- Investigate Urgent
- Investigate Body
- Investigate Around
- Investigate Attack
The inital Sub Goal for all AI is Wait And Attack.
Unknown Sub Goal
TODO: Write this section
Provoke Attack Sub Goal
TODO: Write this section
Avoid Jump Kick Sub Goal
TODO: Write this section
Knock Off Ledge Sub Goal
TODO: Write this section
Wait And Attack Sub Goal
TODO: Write this section
Rush And Attack Sub Goal
TODO: Write this section
Defend Sub Goal
TODO: Write this section
Surround Target Sub Goal
TODO: Write this section
Escape Surround Sub Goal
TODO: Write this section
Investigate Slow Sub Goal
TODO: Write this section
Investigate Urgent Sub Goal
TODO: Write this section
Investigate Body Sub Goal
TODO: Write this section
Investigate Around Sub Goal
TODO: Write this section
Investigate Attack Sub Goal
TODO: Write this section