RadiusProximity.java

/*******************************************************************************
 * Copyright 2014 See AUTHORS file.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *   http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 ******************************************************************************/

package com.badlogic.gdx.ai.steer.proximities;

import com.badlogic.gdx.ai.GdxAI;
import com.badlogic.gdx.ai.Timepiece;
import com.badlogic.gdx.ai.steer.Steerable;
import com.badlogic.gdx.math.Vector;

/** A {@code RadiusProximity} elaborates any agents contained in the specified list that are within the radius of the owner.
 * <p>
 * Note that this implementation checks the AI time of the current frame through the {@link Timepiece#getTime()
 * GdxAI.getTimepiece().getTime()} method in order to calculate neighbors only once per frame (assuming delta time is always
 * greater than 0, if time has changed the frame has changed too). This means that
 * <ul>
 * <li>if you forget to {@link Timepiece#update(float) update the timepiece} on each frame the proximity instance will be
 * calculated only the very first time, which is not what you want of course.</li>
 * <li>ideally the timepiece should be updated before the proximity is updated by the {@link #findNeighbors(ProximityCallback)}
 * method.</li>
 * </ul>
 * 
 * @param <T> Type of vector, either 2D or 3D, implementing the {@link Vector} interface
 * 
 * @author davebaol */
public class RadiusProximity<T extends Vector<T>> extends ProximityBase<T> {

	/** The radius of this proximity. */
	protected float radius;

	private float lastTime;

	/** Creates a {@code RadiusProximity} for the specified owner, agents and radius.
	 * @param owner the owner of this proximity
	 * @param agents the agents
	 * @param radius the radius of the cone area */
	public RadiusProximity (Steerable<T> owner, Iterable<? extends Steerable<T>> agents, float radius) {
		super(owner, agents);
		this.radius = radius;
		this.lastTime = 0;
	}

	/** Returns the radius of this proximity. */
	public float getRadius () {
		return radius;
	}

	/** Sets the radius of this proximity. */
	public void setRadius (float radius) {
		this.radius = radius;
	}

	@Override
	public int findNeighbors (ProximityCallback<T> callback) {
		int neighborCount = 0;

		// If the frame is new then avoid repeating calculations
		// when this proximity is used by multiple group behaviors.
		float currentTime = GdxAI.getTimepiece().getTime();
		if (this.lastTime != currentTime) {
			// Save the current time
			this.lastTime = currentTime;

			T ownerPosition = owner.getPosition();

			// Scan the agents searching for neighbors
			for (Steerable<T> currentAgent : agents) {
				// Make sure the agent being examined isn't the owner
				if (currentAgent != owner) {
					float squareDistance = ownerPosition.dst2(currentAgent.getPosition());

					// The bounding radius of the current agent is taken into account
					// by adding it to the range
					float range = radius + currentAgent.getBoundingRadius();

					// If the current agent is within the range, report it to the callback
					// and tag it for further consideration.
					if (squareDistance < range * range) {
						if (callback.reportNeighbor(currentAgent)) {
							currentAgent.setTagged(true);
							neighborCount++;
							continue;
						}
					}
				}

				// Clear the tag
				currentAgent.setTagged(false);
			}
		} else {
			// Scan the agents searching for tagged neighbors
			for (Steerable<T> currentAgent : agents) {
				// Make sure the agent being examined isn't the owner and that
				// it's tagged.
				if (currentAgent != owner && currentAgent.isTagged()) {

					if (callback.reportNeighbor(currentAgent)) {
						neighborCount++;
					}
				}
			}
		}

		return neighborCount;
	}

}