先把代码贴上来：
import java.applet.Applet;
import java.awt.BorderLayout;
import java.awt.Frame;
import java.awt.GraphicsConfiguration;

import javax.media.j3d.Alpha;
import javax.media.j3d.Appearance;
import javax.media.j3d.BoundingSphere;
import javax.media.j3d.BranchGroup;
import javax.media.j3d.Canvas3D;
import javax.media.j3d.ColoringAttributes;
import javax.media.j3d.PositionPathInterpolator;
import javax.media.j3d.RotPosPathInterpolator;
import javax.media.j3d.Transform3D;
import javax.media.j3d.TransformGroup;
import javax.vecmath.AxisAngle4f;
import javax.vecmath.Point3f;
import javax.vecmath.Quat4f;
import javax.vecmath.Vector3f;

import com.sun.j3d.utils.applet.MainFrame;
import com.sun.j3d.utils.behaviors.vp.OrbitBehavior;
import com.sun.j3d.utils.geometry.ColorCube;
import com.sun.j3d.utils.geometry.Sphere;
import com.sun.j3d.utils.universe.SimpleUniverse;
import com.sun.j3d.utils.universe.Viewer;
import com.sun.j3d.utils.universe.ViewingPlatform;
/**
 * 用这个类尝试将立方体旋转后做动画。
 *
 */
public class RotateTest extends Applet 
{
    public RotateTest() 
    {
        setLayout(new BorderLayout());
        GraphicsConfiguration config=SimpleUniverse.getPreferredConfiguration();
        Canvas3D canvas3D=new Canvas3D(config);
        add("Center",canvas3D);
        
        Viewer mainViewer=new Viewer(canvas3D);//主Viewer
        ViewingPlatform mainViewingPlatform=new ViewingPlatform();//主ViewingPlatfor
m
        
        Vector3f mainViewPoint=new Vector3f(0f,0f,12f);//这里实现主ViewingPlatform的
平移。
        Transform3D t=new Transform3D();
        t.setTranslation(mainViewPoint);
        TransformGroup transformGroup=mainViewingPlatform.getViewPlatformTransform()
;//getViewPlatform函数返回TransformGroup
        transformGroup.setTransform(t);
        
        SimpleUniverse simpleUniverse=new SimpleUniverse(mainViewingPlatform,mainVie
wer);
        
        BranchGroup scene=createSceneGraph();
        simpleUniverse.addBranchGraph(scene);
    
}
     public BranchGroup createSceneGraph() 
     {
            BranchGroup objRoot = new BranchGroup();
            TransformGroup TG=new TransformGroup();
            TG.setCapability(TransformGroup.ALLOW_TRANSFORM_READ);
            TG.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);
            Transform3D tt=new Transform3D();//平移
            Vector3f v3=new Vector3f(0f,-1f,0f);
            tt.setTranslation(v3);
            TG.setTransform(tt);
            objRoot.addChild(TG);
            TG.addChild(new ColorCube(0.5));
            
            //添加黑色球
            TransformGroup sphereTG=new TransformGroup();
            Transform3D spherett=new Transform3D();
            Vector3f spherev3=new Vector3f(0f,0.5f,0.5f);
            spherett.setTranslation(spherev3);
            sphereTG.setTransform(spherett);
            Appearance sphereAppear = new Appearance();
            ColoringAttributes sphereCA = new ColoringAttributes();
            sphereCA.setColor(0.0f, 0.0f, 0.0f);
            sphereAppear.setColoringAttributes(sphereCA);
            sphereTG.addChild(new Sphere(0.1f,sphereAppear));
            TG.addChild(sphereTG);
            
//            动画的PositionPathInterpolator节点。
            Alpha alpha = new Alpha(1, 5000);
            Transform3D axisOfPos = new Transform3D();     
            float[] knots = {0.0f,0.5f, 1.0f};
            
            Point3f[] position = new Point3f[3];
            position[0]=new Point3f(0f,-1f,0f);
            position[1]=new Point3f(0f,1f,0f);
            position[2]=new Point3f(1f,1f,0f);
            
            Quat4f[] quats = new Quat4f[3];
            quats[0] = new Quat4f(0.0f, 0.0f, 0.0f, 0.0f);
            quats[1] = new Quat4f(0.0f, 0.0f, 0.0f, 0.0f);
            quats[2] = new Quat4f(0.0f, 0.0f, 0.0f, 0.0f);
            
            AxisAngle4f axis = new AxisAngle4f(1.0f,0.0f,0.0f,0.0f);
            axisOfPos.set(axis);
            RotPosPathInterpolator rotPosPath = new RotPosPathInterpolator(
                    alpha, TG, axisOfPos, knots, quats, position);
            rotPosPath.setSchedulingBounds(new BoundingSphere());
            objRoot.addChild(rotPosPath);
            
            return objRoot;
     }

    
    public static void main(String[] args) 
    {
        Frame frame = new MainFrame(new RotateTest(), 500, 500);
    }

} 
我的想法是在立方体运动到第二个点后旋转90度，以便继续向第三个点运动时仍然保持带
黑色点那头朝向第三个点，只是模糊的知道应该修改Quats和AxisAngle4f，但因为不清楚
这两个类各个参数的意义，不知道该怎样改，请高手指点。