view_follow.java

一个java3D的动画程序

/*
 * Created on 2005-7-18
 *
 * TODO To change the template for this generated file go to
 * Window - Preferences - Java - Code Style - Code Templates
 */
package View_Autoget;

import javax.media.j3d.Alpha;
import javax.media.j3d.BoundingSphere;
import javax.media.j3d.BranchGroup;
import javax.media.j3d.Canvas3D;
import javax.media.j3d.PhysicalBody;
import javax.media.j3d.PhysicalEnvironment;
import javax.media.j3d.PositionPathInterpolator;
import javax.media.j3d.Transform3D;
import javax.media.j3d.TransformGroup;
import javax.media.j3d.View;
import javax.media.j3d.ViewPlatform;
import javax.vecmath.Point3d;
import javax.vecmath.Point3f;
import javax.vecmath.Quat4f;
import com.sun.j3d.utils.geometry.ColorCube; 
import javax.media.j3d.RotPosPathInterpolator;
/**
 * @author carso
 *
 * TODO To change the template for this generated type comment go to
 * Window - Preferences - Java - Code Style - Code Templates
 */
public class View_follow {
	/*
	 * float radius = 5.0f;
	 * int sections = 90;
	 * int period = 10000;
	 * //Array to store the coordinates along the circumpherence
	 * Point3f[] positions = new Point3f[sections + 1];
	 * //Array containing relative time stamps in the range 0.0..1.0
	 * //Constant velocity if the scale is linear
	 * float[] knots = new float[sections + 1];
	 * Quat4f[] quats = new Quat4f[sections + 1];
	 * 	
	 * 注意：在使用View_follow之前请先确定已经设置好了knots,quats,sections
	 * 否则，可能会出现NullPointerException之类的异常
	*/
	private int sections;
	private Point3f[] positions;
	private float[] knots;
	private Quat4f[] quats;
	private int period;
	
	public void  setKnots(float[] knot){
		this.knots=knot;
	}
	public void  setQuats(Quat4f[] quat){
		this.quats=quat;
	}
	public void  setPositions(Point3f[] position){
		this.positions=position;
	}
	public View_follow(int section){
		this.sections=section;
		positions = new Point3f[sections + 1];
		knots = new float[sections + 1];
		quats = new Quat4f[sections + 1];
		period = 10000;
	}
	public BranchGroup createViewGraph(Canvas3D canvas,TransformGroup tg) {
		// All according to cookbook recipe
		BranchGroup objRoot = new BranchGroup();
		View view = new View();
		ViewPlatform viewPlatform = new ViewPlatform();
		//view.setViewPolicy();
		PhysicalBody physicalBody = new PhysicalBody();
		PhysicalEnvironment physicalEnvironment = new PhysicalEnvironment();
		view.addCanvas3D(canvas);
		view.setPhysicalBody(physicalBody);
		view.setPhysicalEnvironment(physicalEnvironment);
		view.attachViewPlatform(viewPlatform);
		
		//The TransformGroup must be inserted into the BranchGraph
		objRoot.addChild(tg);
		
		// Here, the interpolators are defined, that modify tg. tgRot becomes
		// the TransformGroup to which the ViewPlatform is attached.
		
		TransformGroup tgRot = createDynamicTransform(tg, objRoot);
		tgRot.addChild(viewPlatform);
		objRoot.compile();
		return objRoot;
		
}

public TransformGroup createDynamicTransform (TransformGroup orbitTG, BranchGroup objRoot) {
		
		
		
		//Computing positions and their time stamps. To close the circle, the
		//last point equals the first
		/*以下代码设置是作为围绕一个特定物体(点)旋转的坐标
		for (int i = 0; i <= sections; i++) {
		positions[i] = new Point3f(
				(float)Math.sin(i * 2 * Math.PI / sections) * radius,
				 0.0f,
				(float)Math.cos(i * 2 * Math.PI / sections) * radius
				);
		
		knots[i] = i * (1.0f / sections);
		}
		*/
		
		/*设置好position[]和knots[],此处的代码已经移到了Axis_info.Axis_info中
		float j=-52.0f;
		for(int i=0;i<=sections;i++)
		{
			positions[i]=new Point3f(
			j+i,
			3.0f,
			5.0f
			);
			quats[i]=new Quat4f(0.0f,i,0.0f,0.0f);
			knots[i]=i*(1.0f/sections);
		}*/
		Transform3D orbit_temp=new Transform3D();
		//orbitTG.setTransform(orbit_temp);
		orbit_temp.rotY(1.57);
		//Define PositionPathInterpolator
		//orbitTG is the TransformGroup to which the ViewPlatform is attached
		
		//用PositionPathInterpolator也能实现跟随效果
		//此处实现的是摄象头的移动，要实现物体跟随的效果，物体运动的诡计需要与此处摄象头移动的
		//轨迹吻合
		PositionPathInterpolator rotOrbitInt = new PositionPathInterpolator(
		//RotPosPathInterpolator rotOrbitInt = new RotPosPathInterpolator(
		new Alpha(-1, period),
		orbitTG, // target
		orbit_temp, // identity
		knots,
		//quats,
		positions);
		rotOrbitInt.setSchedulingBounds(new BoundingSphere(new Point3d(0.0, 0.0, 0.0), 400.0));
		
		//Define new TransformGroup and RotationInterpolator
		TransformGroup tgRot = new TransformGroup();
		tgRot.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);
		tgRot.addChild(new ColorCube());
		/*
		RotationInterpolator rotYInt = new RotationInterpolator(
		new Alpha(-1, period),
		tgRot
		);
		rotYInt.setSchedulingBounds(new BoundingSphere(new Point3d(0.0, 0.0, 0.0), 10.0));
		*/
		//Add the two interpolators to the BranchGroup
		objRoot.addChild(rotOrbitInt);
		//objRoot.addChild(rotYInt);
		//objRoot.addChild(rotYInt);
		
		
		orbitTG.addChild(tgRot);
		
		return tgRot;
		}
	
}