Mine

package it.classx.util.java3d;

import java.awt.Frame;
import java.awt.GraphicsConfiguration;
import java.awt.GraphicsEnvironment;
import java.awt.image.BufferedImage;

import javax.media.j3d.Canvas3D;
import javax.media.j3d.GraphicsConfigTemplate3D;
import javax.media.j3d.ImageComponent2D;
import javax.media.j3d.Raster;
import javax.vecmath.Point3f;

import sun.misc.Perf;
import sun.misc.PerformanceLogger;

import com.sun.j3d.utils.universe.SimpleUniverse;

/**
* PictureGrabber is designed to be used as an offscreen canvas which can take a
* picture of a model with an alpha masked background. This is done by reading
* the canvas into a raster with a depth componant, and then checking which
* pixels were written too and which were not.
* 
*/

public class PictureGrabberCanvas3D extends Canvas3D
{
private int width;
private int height;
private ImageComponent2D offscreenBuffer;
private BufferedImage pic;

// construct the grabber
public PictureGrabberCanvas3D(GraphicsConfiguration config, int width, int height)
{ 
super(config, true);

this.width = width;
this.height = height;

this.getScreen3D().setPhysicalScreenWidth(0.0254 / 90.0 * width);
this.getScreen3D().setPhysicalScreenHeight(0.0254 / 90.0 * height);
this.getScreen3D().setSize(width, height);

// create the offscreen buffer
pic = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
offscreenBuffer = new ImageComponent2D(ImageComponent2D.FORMAT_RGB, pic, true, false);
this.setOffScreenBuffer(offscreenBuffer);
offscreenBuffer.setCapability(ImageComponent2D.ALLOW_IMAGE_READ);

}

private static GraphicsConfiguration getOffscreenGraphicsConfig()
{
GraphicsConfigTemplate3D template = new GraphicsConfigTemplate3D();
template.setDoubleBuffer(GraphicsConfigTemplate3D.UNNECESSARY);
template.setSceneAntialiasing(GraphicsConfigTemplate3D.PREFERRED);
GraphicsConfiguration gcfg = GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice().getBestConfiguration(template);
return gcfg;
}


/**
* This will take the picture immediately by forcing a frame draw. This is
* only acceptable if the canvas is an offscreen canvas.
*/
public BufferedImage takePicture()
{ 
long f = Perf.getPerf().highResFrequency();
long c = Perf.getPerf().highResCounter();
renderOffScreenBuffer();
waitForOffScreenRendering();
System.out.println((Perf.getPerf().highResCounter()-c)*1000/f);
return pic;
}
}