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发信人: vrml (3d), 信区: Java
标  题: JAVA3D学习系列(9)--面的生成(上)
发信站: BBS 水木清华站 (Fri Apr  9 15:27:22 1999)

        JAVA3D学习系列(9)----- 面的生成(上)

    汕头大学机电系    张杰（jzhang@mailserv.stu.edu.cn）

一. 生成平面的对象及其定义
    JAVA3D可通过编程显示出面来，面有两种：三角形和四边形，
相应的对象为Triangle和Quad。
    JAVA3D用于生成平面的对象有:
1.  TriangleArray
    TriangleArray (int vertexCount, int vertexFormat )

2.  QuadArray
    QuadArray (int vertexCount, int vertexFormat )

3.  TriangleStripArray
    TriangleStripArray ( int vertexCount , int vertexFormat,
                         int[] stripVertexCounts )

4.  TriangleFanArray
    TriangleFanArray ( int vertexCount ,int vetexFormat,
                       int[] stripVertexCounts )

5.  IndexedTriangleArray
    IndexedTriangleArray (int vertexCount , int vertexFormat,
                          int indexCount)

6.  IndexedQuadArray
    IndexedQuadArray (int vertexCount , int vertexFormat,
                      int indexCount )

7.  IndexedTriangleStripArray
    IndexedTriangleStripArray( int vertexCount, int vertexFormat,
                               int indexCount, int stripIndexCounts[])

8.  IndexedTriangleFanArray
    IndexedTriangleFanArray ( int vertexCount, int vertexFormat,
                              int indexCount, int stripIndexCounts[])

二. TriangleArray生成的面
    和前面介绍的PointArray、LineArray一样，面也可以用
TriangleArray来生成，利用它可以生成三角片面我们先看一下TriangleArray的定义：
        TriangleArray (int vertexCount, int vertexFormat )
    这里：
        vertexCount表示顶点的个数（必须为三的倍数）
        vertexFormat表示顶点的格式（第七讲有介绍）
    下面我们看一个利用TriangleArray的例子，例子里有九个点。

      --1--         --4--      --7--

--0--        --3--        --6--

      --2--         --5--      --8--

//triShape1.java
import javax.media.j3d.*;

public class triShape1 extends Shape3D {

    private float vert[] = {
        -.8f , .0f ,0.0f,
        -.4f , .8f ,0.0f,
        -.4f , -.8f,0.0f,
        -.2f , .0f ,0.0f,
        0.2f , .8f ,0.0f,
        0.2f , -.8f,0.0f,
        0.4f , .0f ,0.0f,
        0.8f , .8f ,0.0f,
        0.8f , -.8f,0.0f,
       };

    private float color[] = {
        0.0f,0.5f,1.0f,
        0.5f,0.0f,1.0f,
        0.0f,0.8f,2.0f,
        1.0f,0.0f,0.3f,
        0.0f,1.0f,0.3f,
        0.3f,0.8f,0.0f,
        0.0f,0.5f,1.0f,
        0.5f,0.0f,1.0f,
        0.0f,0.8f,2.0f,e3D {
    int StripCount[] = new int[2];
     private float vert[] = {
         -.6f ,  .8f , 0.0f,
         -.6f , -.8f,  0.2f,
        -0.2f ,  .5f,  -.2f,
        -0.2f , -.5f , 0.2f,
         0.0f , -.5f,  -.2f,
         0.0f ,  .5f ,  .2f,
         0.2f ,  .0f,   .0f,
         0.2f ,  .8f , 0.3f,
         0.2f , -.8f, -0.3f,
         0.6f ,  .8f,  0.0f,
         0.6f , -.8f,  0.5f,
         0.8f , 0.0f ,  .3f
         };

    private float color[] = {
        1.0f,0.5f,0.0f,
        1.0f,0.0f,0.5f,
        1.0f,0.8f,0.0f,
        5.0f,1.0f,0.0f,
        0.0f,1.0f,0.5f,
        0.9f,1.0f,0.0f,
        0.5f,0.0f,1.0f,
        0.0f,0.5f,1.0f,
        1.0f,0.5f,0.0f,
        1.0f,0.0f,0.5f,
        1.0f,0.8f,0.0f,
      };

    public triShape3() {
        StripCount[0] = 7;
        StripCount[1] = 5;
        TriangleStripArray tri = new TriangleStripArray(12,
             TriangleStripArray.COORDINATES|
                      TriangleStripArray.COLOR_3 , StripCount);
          tri.setCoordinates(0,vert);
          tri.setColors(0,color);
        PolygonAttributes pa = new PolygonAttributes();
          pa.setCullFace(PolygonAttributes.CULL_NONE);
        Appearance ap = new Appearance();
          ap.setPolygonAttributes(pa);
        this.setGeometry(tri);
        this.setAppearance(ap);
        this.setGeometry(tri);
     }
}
//end of triShape3.java

五. TriangleFanArray生成的面
    TriangleFanArray对象的定义为：
    TriangleFanArray ( int vertexCount ,int vetexFormat,
                       int[] stripVertexCounts )
    利用TriangleFanArray对象，我们可以生成多组三角片面，每组
三角片面占用一定数量的顶点，每个组在生成三角片面时，头三个顶
点构成一个三角片面，其余的顶点和前面的顶点及每组第一个顶点生成
一个三角片面。下面的triShape4.java程序中，我们生成了两组三角
片面，头5个点生成了三个相连的三角片面，后6个点生成了四个相连的
三角片面。形状就像两把扇子，一大一小。
//triShape4.java

import javax.media.j3d.*;

public class triShape4 extends Shape3D {
    int FanCount[] = new int[2];
     private float vert[] = {
              0.0f , 0.0f , 0.0f,
              -0.3f , 0.3f , 0.02f,
              -0.1f , 0.4f , -0.02f,
               0.1f , 0.4f ,  0.02f,
               0.3f,  0.3f ,  -0.02f,
               0.0f, -0.8f ,  0.0f,
              -0.6f, -0.2f,  0.02f,
              -0.3f, -0.1f , -0.02f,
                 .0f, -0.05f, 0.02f,
                 .3f, -0.1f, -0.02f,
                 .6f, -0.2f,  0.02f
          };

    private float color[] = {
        1.0f,0.5f,0.0f,
        1.0f,0.0f,0.5f,
        1.0f,0.8f,0.0f,
        5.0f,1.0f,0.0f,
        0.0f,1.0f,0.5f,
        0.9f,1.0f,0.0f,
        0.5f,0.0f,1.0f,
        0.0f,0.5f,1.0f,
       1.0f,0.5f,0.0f,
        1.0f,0.0f,0.5f,
      };

    public triShape4() {
        FanCount[0] = 5;
        FanCount[1] = 6;
        TriangleFanArray tri = new TriangleFanArray(11,
             TriangleFanArray.COORDINATES|
                      TriangleFanArray.COLOR_3 , FanCount);
          tri.setCoordinates(0,vert);
          tri.setColors(0,color);
        PolygonAttributes pa = new PolygonAttributes();
          pa.setCullFace(PolygonAttributes.CULL_NONE);
        Appearance ap = new Appearance();
          ap.setPolygonAttributes(pa);
        this.setGeometry(tri);
        this.setAppearance(ap);
        this.setGeometry(tri);
     }
}
//end of triShape4.java

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