OpenGL ES 只能通過(guò)繪制三角形來(lái)構(gòu)造幾何圖形，比如前面繪制的 20 面體 Android OpenGL ES 開(kāi)發(fā)教程(12)：繪制一個(gè) 20 面體，通過(guò)增加正多面體的邊數(shù)，就可以構(gòu)造出一個(gè)球體：

http://wiki.jikexueyuan.com/project/opengl-es-guide/images/89.png" alt="" />

在項(xiàng)目中創(chuàng)建一個(gè) Sphere 類，它的 Draw 方法，通過(guò)繪制三角形來(lái)構(gòu)造球體，并且為其添加法線，法線主要用于光照效果，將在后面介紹。

public void draw(GL10 gl) {
 float    theta, pai;
 float    co, si;
 float    r1, r2;
 float    h1, h2;
 float    step = 2.0f;
 float[][] v = new float[32][3];
 ByteBuffer vbb;
 FloatBuffer vBuf;
 vbb = ByteBuffer.allocateDirect(v.length \* v[0].length \* 4);
 vbb.order(ByteOrder.nativeOrder());
 vBuf = vbb.asFloatBuffer();
 gl.glEnableClientState(GL10.GL\_VERTEX\_ARRAY);
 gl.glEnableClientState(GL10.GL\_NORMAL\_ARRAY);
 for (pai = -90.0f; pai < 90.0f; pai += step) {
 int    n = 0;
 r1 = (float)Math.cos(pai \* Math.PI / 180.0);
 r2 = (float)Math.cos((pai + step) \* Math.PI / 180.0);
 h1 = (float)Math.sin(pai \* Math.PI / 180.0);
 h2 = (float)Math.sin((pai + step) \* Math.PI / 180.0);
 for (theta = 0.0f; theta <= 360.0f; theta += step) {
 co = (float)Math.cos(theta \* Math.PI / 180.0);
 si = -(float)Math.sin(theta \* Math.PI / 180.0);
 v[n][0] = (r2 \* co);
 v[n][1] = (h2);
 v[n][2] = (r2 \* si);
 v[n + 1][0] = (r1 \* co);
 v[n + 1][1] = (h1);
 v[n + 1][2] = (r1 \* si);
 vBuf.put(v[n]);
 vBuf.put(v[n + 1]);
 n += 2;
 if(n>31){
 vBuf.position(0);
 gl.glVertexPointer(3, GL10.GL\_FLOAT, 0, vBuf);
 gl.glNormalPointer(GL10.GL\_FLOAT, 0, vBuf);
 gl.glDrawArrays(GL10.GL\_TRIANGLE\_STRIP, 0, n);
 n = 0;
 theta -= step;
 }
 }
 vBuf.position(0);
 gl.glVertexPointer(3, GL10.GL\_FLOAT, 0, vBuf);
 gl.glNormalPointer(GL10.GL\_FLOAT, 0, vBuf);
 gl.glDrawArrays(GL10.GL\_TRIANGLE\_STRIP, 0, n);
 }
 gl.glDisableClientState(GL10.GL\_VERTEX\_ARRAY);
 gl.glDisableClientState(GL10.GL\_NORMAL\_ARRAY);
}  

有了 Sphere 類，創(chuàng)建一個(gè) DrawSphere Activity 來(lái)繪制球體，為了能看出 3D 效果，給場(chǎng)景中添加光源（后面介紹）

public void DrawScene(GL10 gl) {
 super.DrawScene(gl);
 initScene(gl);
 sphere.draw(gl);
}  

http://wiki.jikexueyuan.com/project/opengl-es-guide/images/90.png" alt="" />

本例下載