Billboard.java

/*******************************************************************************
 * Copyright 2015 See AUTHORS file.
 * <p/>
 * 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
 * <p/>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p/>
 * 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.mygdx.game.objects;

import com.badlogic.gdx.graphics.Camera;
import com.badlogic.gdx.graphics.g3d.Model;
import com.badlogic.gdx.math.Matrix4;
import com.badlogic.gdx.math.Quaternion;
import com.badlogic.gdx.math.Vector3;

/**
 * A simple billboard-like class which rotates a model to face the camera on update.
 *
 * @author jsjolund
 */
public class Billboard extends GameModel {

	private final Vector3 offset = new Vector3();
	private final Vector3 worldPos = new Vector3();
	private final Quaternion quat = new Quaternion();
	private boolean faceUp;
	private Matrix4 followTransform;
	private Camera camera;

	/**
	 * @param model           The model which is to be instantiated
	 * @param name              Id of the model (doesn't really matter)
	 * @param camera          The camera which the billboard should face
	 * @param faceUp          If true, the model will always face the Y-axis, but otherwise rotate with the camera
	 * @param followTransform The billboard will follow the translation of this matrix
	 * @param offset          Constant offset from the follow-matrix translation
	 */
	public Billboard(Model model, String name, Camera camera, boolean faceUp, Matrix4 followTransform, Vector3 offset) {
		super(model, name, followTransform.getTranslation(new Vector3()), new Vector3(), new Vector3(1, 1, 1));
		this.faceUp = faceUp;
		this.offset.set(offset);
		this.followTransform = followTransform;
		this.camera = camera;
	}

	public void setCamera(Camera camera) {
		this.camera = camera;
	}

	public void setFollowTransform(Matrix4 followTransform, Vector3 offset) {
		this.followTransform = followTransform;
		this.offset.set(offset);
	}

	@Override
	public void update(float deltaTime) {
		super.update(deltaTime);
		followTransform.getTranslation(worldPos);
		camera.view.getRotation(quat).conjugate();
		if (faceUp) {
			modelInstance.transform.setFromEulerAngles(quat.getYaw(), -90, quat.getRoll());
		} else {
			modelInstance.transform.set(quat);
		}
		modelInstance.transform.setTranslation(worldPos.add(offset));
	}
}