com.badlogic.gdx.ai.steer.behaviors.FollowFlowField Maven / Gradle / Ivy
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* Copyright 2014 See AUTHORS file.
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* Licensed under the Apache License, Version 2.0 (the "License");
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* http://www.apache.org/licenses/LICENSE-2.0
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package com.badlogic.gdx.ai.steer.behaviors;
import com.badlogic.gdx.ai.steer.Limiter;
import com.badlogic.gdx.ai.steer.Steerable;
import com.badlogic.gdx.ai.steer.SteeringAcceleration;
import com.badlogic.gdx.ai.steer.SteeringBehavior;
import com.badlogic.gdx.math.Vector;
/** The {@code FollowFlowField} behavior produces a linear acceleration that tries to align the motion of the owner with the local
* tangent of a flow field. The flow field defines a mapping from a location in space to a flow vector. Any flow field can be used
* as the basis of this steering behavior, although it is sensitive to discontinuities in the field.
*
* For instance, flow fields can be used for simulating various effects, such as magnetic fields, an irregular gust of wind or the
* meandering path of a river. They can be generated by a simple random algorithm, a Perlin noise or a complicated image
* processing. And of course flow fields can be dynamic. The only limit is your imagination.
*
* Like {@link FollowPath}, this behavior can work in a predictive manner when its {@code predictionTime} is greater than 0.
*
* @param Type of vector, either 2D or 3D, implementing the {@link Vector} interface
*
* @author davebaol */
public class FollowFlowField> extends SteeringBehavior {
/** The flow field to follow. */
protected FlowField flowField;
/** The time in the future to predict the owner's position. Set it to 0 for non-predictive flow field following. */
protected float predictionTime;
/** Creates a non-predictive {@code FollowFlowField} for the specified owner.
* @param owner the owner of this behavior */
public FollowFlowField (Steerable owner) {
this(owner, null);
}
/** Creates a non-predictive {@code FollowFlowField} for the specified owner and flow field. Prediction time defaults to 0.
* @param owner the owner of this behavior
* @param flowField the flow field to follow */
public FollowFlowField (Steerable owner, FlowField flowField) {
this(owner, flowField, 0);
}
/** Creates a {@code FollowFlowField} with the specified owner, flow field and prediction time.
* @param owner the owner of this behavior
* @param flowField the flow field to follow
* @param predictionTime the time in the future to predict the owner's position. Can be 0 for non-predictive flow field
* following. */
public FollowFlowField (Steerable owner, FlowField flowField, float predictionTime) {
super(owner);
this.flowField = flowField;
this.predictionTime = predictionTime;
}
@Override
protected SteeringAcceleration calculateRealSteering (SteeringAcceleration steering) {
// Clear both linear and angular components
steering.setZero();
// Predictive or non-predictive behavior?
T location = (predictionTime == 0) ?
// Use the current position of the owner
owner.getPosition()
:
// Calculate the predicted future position of the owner. We're reusing steering.linear here.
steering.linear.set(owner.getPosition()).mulAdd(owner.getLinearVelocity(), predictionTime);
// Retrieve the flow vector at the specified location
T flowVector = flowField.lookup(location);
if (flowVector != null && !flowVector.isZero()) {
Limiter actualLimiter = getActualLimiter();
// Calculate linear acceleration
steering.linear.mulAdd(flowVector, actualLimiter.getMaxLinearSpeed()).sub(owner.getLinearVelocity())
.limit(actualLimiter.getMaxLinearAcceleration());
}
// Output steering
return steering;
}
/** Returns the flow field of this behavior */
public FlowField getFlowField () {
return flowField;
}
/** Sets the flow field of this behavior
* @param flowField the flow field to set
* @return this behavior for chaining */
public FollowFlowField setFlowField (FlowField flowField) {
this.flowField = flowField;
return this;
}
/** Returns the prediction time. */
public float getPredictionTime () {
return predictionTime;
}
/** Sets the prediction time. Set it to 0 for non-predictive flow field following.
* @param predictionTime the predictionTime to set
* @return this behavior for chaining. */
public FollowFlowField setPredictionTime (float predictionTime) {
this.predictionTime = predictionTime;
return this;
}
//
// Setters overridden in order to fix the correct return type for chaining
//
@Override
public FollowFlowField setOwner (Steerable owner) {
this.owner = owner;
return this;
}
@Override
public FollowFlowField setEnabled (boolean enabled) {
this.enabled = enabled;
return this;
}
/** Sets the limiter of this steering behavior. The given limiter must at least take care of the maximum linear speed and
* acceleration.
* @return this behavior for chaining. */
@Override
public FollowFlowField setLimiter (Limiter limiter) {
this.limiter = limiter;
return this;
}
/** A {@code FlowField} defines a mapping from a location in space to a flow vector. Typically flow fields are implemented as a
* multidimensional array representing a grid of cells. In each cell of the grid lives a flow vector.
*
* @param Type of vector, either 2D or 3D, implementing the {@link Vector} interface
*
* @author davebaol */
public interface FlowField> {
/** Returns the flow vector for the specified position in space.
* @param position the position to map */
public T lookup (T position);
}
}