Java3D中平行光投影的实现

import java.applet.Applet;

import java.awt.BorderLayout;

import java.awt.GraphicsConfiguration;

import java.awt.Label;

import com.sun.j3d.utils.applet.MainFrame;

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

import com.sun.j3d.utils.geometry.*;

import javax.media.j3d.*;

import javax.vecmath.*;

public class SimpleShadow extends Applet{

//三角平面类

public class TriPlane extends Shape3D{

TriPlane(Point3f A,Point3f B,Point3f C){

this.setGeometry(this.createGeometry3(A,B,C));

this.setAppearance(this.createAppearance());

}

//建立三角平面  

Geometry createGeometry3(Point3f A,Point3f B,Point3f C){

TriangleArray plane=new TriangleArray(3,
GeometryArray.COORDINATES|GeometryArray.NORMALS);

//设置平面3个顶点的坐标

plane.setCoordinate(0,A);

plane.setCoordinate(1,B);

plane.setCoordinate(2,C);   

//计算平面法向量

Vector3f a=new Vector3f(A.x-B.x,A.y-B.y,A.z-B.z);

Vector3f b=new Vector3f(C.x-B.x,C.y-B.y,C.z-B.z);

Vector3f n=new Vector3f();

n.cross(b,a);

//法向量单位化

n.normalize();

//设置平面3个顶点的法向量

plane.setNormal(0,n);

plane.setNormal(1,n);

plane.setNormal(2,n);

return plane;

}  

//创建Material不为空的外观  

Appearance createAppearance(){

Appearance appear=new Appearance();

Material material=new Material();

appear.setMaterial(material);

return appear;

}  

} 

//四边平面类

public class QuadPlane extends Shape3D{  

QuadPlane(Point3f A,Point3f B,Point3f C,Point3f D){

this.setGeometry(this.createGeometry4(A,B,C,D));

this.setAppearance(this.createAppearance());

}  

//创建四边性平面

Geometry createGeometry4(Point3f A,Point3f B,Point3f C,Point3f D){

QuadArray plane=new QuadArray(4,GeometryArray.COORDINATES|GeometryArray.NORMALS);

//设置平面3个顶点的坐标

plane.setCoordinate(0,A);

plane.setCoordinate(1,B);

plane.setCoordinate(2,C);

plane.setCoordinate(3,D);

//计算平面法向量

Vector3f a=new Vector3f(A.x-B.x,A.y-B.y,A.z-B.z);

Vector3f b=new Vector3f(C.x-B.x,C.y-B.y,C.z-B.z);

Vector3f n=new Vector3f();

n.cross(b,a);

//法向量单位化

n.normalize();

//设置平面4个顶点的法向量

plane.setNormal(0,n);

plane.setNormal(1,n);

plane.setNormal(2,n);

plane.setNormal(3,n);

return plane;

}

//创建Material不为空的外观  

Appearance createAppearance(){

Appearance appear=new Appearance();

Material material=new Material();

appear.setMaterial(material);

return appear;

}

}  

//阴影类

public class Shadow3D extends Shape3D{

Shadow3D(GeometryArray geom,Vector3f direction,Color3f col,float height){

int vCount=geom.getVertexCount();

TriangleArray poly=new TriangleArray(vCount,
GeometryArray.COORDINATES|GeometryArray.COLOR_3);

int v;

Point3f vertex=new Point3f();

Point3f shadow=new Point3f();   

for(v=0;v<vCount;v++){

//计算可见面顶点在投影面上的投影坐标

geom.getCoordinate(v,vertex);

System.out.println(vertex.y-height);

shadow.set(vertex.x-(vertex.y-height),height+0.0001f,
vertex.z-(vertex.y-height));

poly.setCoordinate(v,shadow);

poly.setColor(v,col);

}

this.setGeometry(poly);   

}

} 

public SimpleShadow(){

this.setLayout(new BorderLayout());

//GraphicsConfiguration config =SimpleUniverse.getPreferredConfiguration();

Canvas3D c=new Canvas3D(null);

this.add("Center",c);

//创建分支节点

BranchGroup scene=new BranchGroup();

//创建三角形可见平面

Shape3D plane=new TriPlane(new Point3f(0.0f,0.6f,-0.2f),
new Point3f(-0.3f,-0.3f,0.2f),
new Point3f(0.6f,-0.3f,0.2f));

//添加到根分支节点

scene.addChild(plane);

//创建四边形投影平面

Shape3D floor=new QuadPlane(new Point3f(-1.0f,-0.5f,-1.0f),
new Point3f(-1.0f,-0.5f,1.0f),new Point3f(1.0f,-0.5f,1.0f),
new Point3f(1.0f,-0.5f,-1.0f));

//添加到根分支节点

scene.addChild(floor);

//添加到环境光

AmbientLight lightA=new AmbientLight();

lightA.setInfluencingBounds(new BoundingSphere());

scene.addChild(lightA);

//添加平行光

DirectionalLight lightD1=new DirectionalLight();

lightD1.setInfluencingBounds(new BoundingSphere());

Vector3f direction=new Vector3f(-1.0f,-1.0f,-1.0f);

//方向矢量单位化

direction.normalize();

lightD1.setDirection(direction);

scene.addChild(lightD1);

//创建阴影物体

Shape3D shadow=new Shadow3D((GeometryArray)plane.getGeometry(),direction,
new Color3f(0.2f,0.2f,0.2f),-0.5f);

scene.addChild(shadow);

SimpleUniverse u=new SimpleUniverse(c);

u.getViewingPlatform().setNominalViewingTransform();

u.addBranchGraph(scene);

} 

public static void main(String argv[]){

new MainFrame(new SimpleShadow(),256,256);

}

}