PrioritySteering (libGDX AI)

java.lang.Object
- com.badlogic.gdx.ai.steer.SteeringBehavior<T>
- - com.badlogic.gdx.ai.steer.behaviors.PrioritySteering<T>

Type Parameters:

T - Type of vector, either 2D or 3D, implementing the Vector interface
```
public class PrioritySteering<T extends com.badlogic.gdx.math.Vector<T>>
extends SteeringBehavior<T>
```
The PrioritySteering behavior iterates through the behaviors and returns the first non zero steering. It makes sense since certain steering behaviors only request an acceleration in particular conditions. Unlike Seek or Evade, which always produce an acceleration, RaycastObstacleAvoidance, CollisionAvoidance, Separation, Hide and Arrive will suggest no acceleration in many cases. But when these behaviors do suggest an acceleration, it is unwise to ignore it. An obstacle avoidance behavior, for example, should be honored immediately to avoid the crash.
Typically the behaviors of a PrioritySteering are arranged in groups with regular blending weights, see BlendedSteering. These groups are then placed in priority order to let the steering system consider each group in turn. It blends the steering behaviors in the current group together. If the total result is very small (less than some small, but adjustable, parameter), then it is ignored and the next group is considered. It is best not to check against zero directly, because numerical instability in calculations can mean that a zero value is never reached for some steering behaviors. Using a small constant value (conventionally called epsilon) avoids this problem. When a group is found with a result that isn't small, its result is used to steer the agent.
For instance, a pursuing agent working in a team may have three priorities:
- a collision avoidance group that contains behaviors for obstacle avoidance, wall avoidance, and avoiding other characters.
- a separation behavior used to avoid getting too close to other members of the chasing pack.
- a pursuit behavior to chase the target.
If the character is far from any interference, the collision avoidance group will return with no desired acceleration. The separation behavior will then be considered but will also return with no action. Finally, the pursuit behavior will be considered, and the acceleration needed to continue the chase will be used. If the current motion of the character is perfect for the pursuit, this behavior may also return with no acceleration. In this case, there are no more behaviors to consider, so the character will have no acceleration, just as if they'd been exclusively controlled by the pursuit behavior.
In a different scenario, if the character is about to crash into a wall, the first group will return an acceleration that will help avoid the crash. The character will carry out this acceleration immediately, and the steering behaviors in the other groups won't be considered.
Usually PrioritySteering gives you a good compromise between speed and accuracy.

Field Summary

Fields
Modifier and Type	Field and Description
`protected com.badlogic.gdx.utils.Array<SteeringBehavior<T>>`	`behaviors` The list of steering behaviors in priority order.
`protected float`	`epsilon` The threshold of the steering acceleration magnitude below which a steering behavior is considered to have given no output.
`protected int`	`selectedBehaviorIndex` The index of the behavior whose acceleration has been returned by the last evaluation of this priority steering.

Fields inherited from class com.badlogic.gdx.ai.steer.SteeringBehavior
enabled, limiter, owner

Constructor Summary

Constructors
Constructor and Description
`PrioritySteering(Steerable<T> owner)` Creates a `PrioritySteering` behavior for the specified owner.
`PrioritySteering(Steerable<T> owner, float epsilon)` Creates a `PrioritySteering` behavior for the specified owner and threshold.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`PrioritySteering<T>`	`add(SteeringBehavior<T> behavior)` Adds the specified behavior to the priority list.
`protected SteeringAcceleration<T>`	`calculateRealSteering(SteeringAcceleration<T> steering)` Calculates the steering acceleration produced by this behavior and writes it to the given steering output.
`float`	`getEpsilon()` Returns the threshold of the steering acceleration magnitude below which a steering behavior is considered to have given no output.
`int`	`getSelectedBehaviorIndex()` Returns the index of the behavior whose acceleration has been returned by the last evaluation of this priority steering; -1 otherwise.
`PrioritySteering<T>`	`setEnabled(boolean enabled)` Sets this steering behavior on/off.
`PrioritySteering<T>`	`setEpsilon(float epsilon)` Sets the threshold of the steering acceleration magnitude below which a steering behavior is considered to have given no output.
`PrioritySteering<T>`	`setLimiter(Limiter limiter)` Sets the limiter of this steering behavior.
`PrioritySteering<T>`	`setOwner(Steerable<T> owner)` Sets the owner of this steering behavior.

Methods inherited from class com.badlogic.gdx.ai.steer.SteeringBehavior
calculateSteering, getActualLimiter, getLimiter, getOwner, isEnabled, newVector

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - epsilon
```
protected float epsilon
```
    The threshold of the steering acceleration magnitude below which a steering behavior is considered to have given no output.
  - behaviors
```
protected com.badlogic.gdx.utils.Array<SteeringBehavior<T extends com.badlogic.gdx.math.Vector<T>>> behaviors
```
    The list of steering behaviors in priority order. The first item in the list is tried first, the subsequent entries are only considered if the first one does not return a result.
  - selectedBehaviorIndex
```
protected int selectedBehaviorIndex
```
    The index of the behavior whose acceleration has been returned by the last evaluation of this priority steering.
- Constructor Detail
  - PrioritySteering
```
public PrioritySteering(Steerable<T> owner)
```
    Creates a PrioritySteering behavior for the specified owner. The threshold is set to 0.001.
    
    Parameters:
    
    owner - the owner of this behavior
  - PrioritySteering
```
public PrioritySteering(Steerable<T> owner,
                        float epsilon)
```
    Creates a PrioritySteering behavior for the specified owner and threshold.
    
    Parameters:
    
    owner - the owner of this behavior
    
    epsilon - the threshold of the steering acceleration magnitude below which a steering behavior is considered to have given no output
- Method Detail
  - add
```
public PrioritySteering<T> add(SteeringBehavior<T> behavior)
```
    Adds the specified behavior to the priority list.
    
    Parameters:
    
    behavior - the behavior to add
    
    Returns:
    
    this behavior for chaining.
  - calculateRealSteering
```
protected SteeringAcceleration<T> calculateRealSteering(SteeringAcceleration<T> steering)
```
    Description copied from class: SteeringBehavior
    
    Calculates the steering acceleration produced by this behavior and writes it to the given steering output.
    This method is called by SteeringBehavior.calculateSteering(SteeringAcceleration) when this steering behavior is enabled.
    
    Specified by:
    
    calculateRealSteering in class SteeringBehavior<T extends com.badlogic.gdx.math.Vector<T>>
    
    Parameters:
    
    steering - the steering acceleration to be calculated.
    
    Returns:
    
    the calculated steering acceleration for chaining.
  - getSelectedBehaviorIndex
```
public int getSelectedBehaviorIndex()
```
    Returns the index of the behavior whose acceleration has been returned by the last evaluation of this priority steering; -1 otherwise.
  - getEpsilon
```
public float getEpsilon()
```
    Returns the threshold of the steering acceleration magnitude below which a steering behavior is considered to have given no output.
  - setEpsilon
```
public PrioritySteering<T> setEpsilon(float epsilon)
```
    Sets the threshold of the steering acceleration magnitude below which a steering behavior is considered to have given no output.
    
    Parameters:
    
    epsilon - the epsilon to set
    
    Returns:
    
    this behavior for chaining.
  - setOwner
```
public PrioritySteering<T> setOwner(Steerable<T> owner)
```
    Description copied from class: SteeringBehavior
    
    Sets the owner of this steering behavior.
    
    Overrides:
    
    setOwner in class SteeringBehavior<T extends com.badlogic.gdx.math.Vector<T>>
    
    Returns:
    
    this behavior for chaining.
  - setEnabled
```
public PrioritySteering<T> setEnabled(boolean enabled)
```
    Description copied from class: SteeringBehavior
    
    Sets this steering behavior on/off.
    
    Overrides:
    
    setEnabled in class SteeringBehavior<T extends com.badlogic.gdx.math.Vector<T>>
    
    Returns:
    
    this behavior for chaining.
  - setLimiter
```
public PrioritySteering<T> setLimiter(Limiter limiter)
```
    Sets the limiter of this steering behavior. However, PrioritySteering needs no limiter at all as it simply returns the first non zero steering acceleration.
    
    Overrides:
    
    setLimiter in class SteeringBehavior<T extends com.badlogic.gdx.math.Vector<T>>
    
    Returns:
    
    this behavior for chaining.

Class PrioritySteering<T extends com.badlogic.gdx.math.Vector<T>>

Field Summary

Fields inherited from class com.badlogic.gdx.ai.steer.SteeringBehavior

Constructor Summary

Method Summary

Methods inherited from class com.badlogic.gdx.ai.steer.SteeringBehavior

Methods inherited from class java.lang.Object

Field Detail

epsilon

behaviors

selectedBehaviorIndex

Constructor Detail

PrioritySteering

PrioritySteering

Method Detail

add

calculateRealSteering

getSelectedBehaviorIndex

getEpsilon

setEpsilon

setOwner

setEnabled

setLimiter