engine/src/core/com/jme3/renderer/queue/TransparentComparator.java

/*
 * Copyright (c) 2009-2010 jMonkeyEngine
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
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 *
 * * Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * * Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 *
 * * Neither the name of 'jMonkeyEngine' nor the names of its contributors
 *   may be used to endorse or promote products derived from this software
 *   without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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 */

package com.jme3.renderer.queue;

import com.jme3.math.Vector3f;
import com.jme3.renderer.Camera;
import com.jme3.scene.Geometry;

public class TransparentComparator implements GeometryComparator {

    private Camera cam;
    private final Vector3f tempVec = new Vector3f();

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

    /**
     * Calculates the distance from a spatial to the camera. Distance is a
     * squared distance.
     *
     * @param spat
     *            Spatial to distancize.
     * @return Distance from Spatial to camera.
     */
    private float distanceToCam2(Geometry spat){
        if (spat == null)
            return Float.NEGATIVE_INFINITY;

        if (spat.queueDistance != Float.NEGATIVE_INFINITY)
            return spat.queueDistance;

        Vector3f camPosition = cam.getLocation();
        Vector3f viewVector = cam.getDirection();
        Vector3f spatPosition = null;

        if (spat.getWorldBound() != null){
            spatPosition = spat.getWorldBound().getCenter();
        }else{
            spatPosition = spat.getWorldTranslation();
        }

        spatPosition.subtract(camPosition, tempVec);
        spat.queueDistance = tempVec.dot(tempVec);

        float retval = Math.abs(tempVec.dot(viewVector)
                / viewVector.dot(viewVector));
        viewVector.mult(retval, tempVec);

        spat.queueDistance = tempVec.length();

        return spat.queueDistance;
    }

    private float distanceToCam(Geometry spat){
        // NOTE: It is best to check the distance
        // to the bound's closest edge vs. the bound's center here.
        return spat.getWorldBound().distanceToEdge(cam.getLocation());
    }

    public int compare(Geometry o1, Geometry o2) {
        float d1 = distanceToCam(o1);
        float d2 = distanceToCam(o2);

        if (d1 == d2)
            return 0;
        else if (d1 < d2)
            return 1;
        else
            return -1;
    }
}