实现生成星星，让星星自转和绕原点公转的简单demo。
物体旋转都用到了gl.glRotatef，然而我们知道旋转函数是绕此时经过绘图原点的轴旋转的，即
gl.glLoadIdentity(); //右移 1.5 单位，并移入屏幕 4.0 gl.glTranslatef(0f, 0f, -4f); //旋转矩阵 gl.glRotatef(rotateTri, 0.0f, 3.0f,0f);绕过点（0，0，-4）的向量（0，3，0）旋转的。星星的公转是绕屏幕中心原点旋转，而绘图和自转都是绕星星本身的中心旋转，因此为了让两个旋转不相互干扰，必须在设置绘图原点和自转之前就进行公转的设定：
gl.glLoadIdentity(); gl.glTranslatef(0f, 0.0f, -deep);//先将屏幕移到深层 gl.glRotatef(start.angle, 0f , 0f, 1f);//函数本身的意思是将图形绕z轴旋转到angle角度，通过修改angle的值来实现公转，此时绘图原点还在屏幕中心 gl.glTranslatef(start.dist*(float)Math.cos(start.angle),start.dist*(float)Math.sin(start.angle), 0);//由于星星初始角度不同，离原点距离不同就会导致其中心位置，即绘图原点的不同，通过角度和离屏幕中心点的距离计算出 gl.glRotatef(rotateY , 1f , 0f, 0f);//绕y轴自转，此时绘图原点已经移到星星自身的中心下面是实现了多个星星在屏幕内旋转和自转的demo：
start类：
public class Start { float dist; int r , g , b; float angle; boolean IsBigging = true;//是否正在背离原点旋转 float rotateSelf; //自转的角速度 float rotateElse; //公转的角速度 public Start (float dist , int r , int g , int b , float angle,float rotateSelf,float rotateElse) { this.dist = dist; this.r = r; this.g = g; this.b = b; this.angle = angle; this.rotateSelf = rotateSelf; this.rotateElse =rotateElse; }}Render类：
package com.example.zp.rotatestartdemo; import android.opengl.GLSurfaceView; import java.nio.FloatBuffer;import java.nio.IntBuffer; import javax.microedition.khronos.egl.EGLConfig;import javax.microedition.khronos.opengles.GL10; /** * Created by lenovo on 2016/9/6. */public class GLRender implements GLSurfaceView.Renderer{ private int numberStarts =50; private Start [] starts = new Start[numberStarts]; private float deep = 6f; private float maxDist = 4f;//屏幕在deep层能显示的最大横坐标，这里表示的是离原点的最大值 private void init() { //初始化星星 for(int i = 0 ; i < numberStarts ; i++) { float dis = 0.2f*i; int r = (int)(Math.random()*256); int g = (int)(Math.random()*256); int b = (int)(Math.random()*256); float angle =(float)(Math.random())*2f*(float)Math.PI; float rotateSelf = (float)(Math.random())*2f*(float)Math.PI/8f; float rotateElse = (float)(Math.random())*2f*(float)Math.PI/16f; starts[i] = new Start(dis , r , g , b , angle,rotateSelf,rotateElse); } } //三角形 FloatBuffer vertices = BufferUtil.floatToBuffer(new float[]{ -0.025f,0.05f,0f, -0.1f,0.05f,0f, -0.05f,-0.025f,0f, -0.1f,-0.1f,0f, 0f,-0.05f,0f, 0.1f,-0.1f,0f, 0.05f,-0.025f,0f, 0.1f,0.05f,0f, 0.025f,0.05f,0f, 0f,0.1f,0f, -0.025f,0.05f,0f });//五边形FloatBuffer vertices2 = BufferUtil.floatToBuffer(new float[]{ -0.025f,0.05f,0f, -0.05f,-0.025f,0f, 0f,-0.05f,0f, -0.025f,0.05f,0f, 0f,-0.05f,0f, 0.025f,0.05f,0f, 0f,-0.05f,0f, 0.05f,-0.025f,0f, 0.025f,0.05f,0f}); @Override public void onSurfaceCreated(GL10 gl, EGLConfig config) { gl.glShadeModel(GL10.GL_SMOOTH); // 黑色背景 gl.glClearColor(0, 0, 0, 0); // 设置深度缓存 gl.glClearDepthf(1.0f);// gl.glEnable(GL10.GL_CULL_FACE);//启用这个后，当目前图片转到背面时候就看不到了，意思就是画一个面，只能从正面看到这个面，从背面就看不到，因此不能随便加 // 启用阴影平滑 // 启用深度测试 gl.glEnable(GL10.GL_DEPTH_TEST); gl.glDepthFunc(GL10.GL_LEQUAL); // 告诉系统对透视进行修正 gl.glHint(GL10.GL_PERSPECTIVE_CORRECTION_HINT, GL10.GL_FASTEST); init(); } @Override public void onSurfaceChanged(GL10 gl, int width, int height) { float ratio = (float) width / height; //设置OpenGL场景的大小 gl.glViewport(0, 0, width, height); //设置投影矩阵 gl.glMatrixMode(GL10.GL_PROJECTION); //重置投影矩阵 gl.glLoadIdentity(); // 设置视口的大小 gl.glFrustumf(-ratio, ratio, -1, 1, 1, 10); // 选择模型观察矩阵 gl.glMatrixMode(GL10.GL_MODELVIEW); // 重置模型观察矩阵 gl.glLoadIdentity(); } @Override public void onDrawFrame(GL10 gl) { // 清除屏幕和深度缓存 gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT); gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); for(int i = 0 ; i < numberStarts ; i++) { drawStart(gl, starts[i]); } gl.glDisableClientState(GL10.GL_VERTEX_ARRAY); } // float rotateSpeed = 0.3f ; float rotateY = 0; public void drawStart(GL10 gl , Start start) { gl.glLoadIdentity(); gl.glTranslatef(0f, 0.0f, -deep); gl.glRotatef(start.angle, 0f , 0f, 1f);//rotateZ gl.glTranslatef(start.dist*(float)Math.cos(start.angle),start.dist*(float)Math.sin(start.angle), 0); gl.glRotatef(rotateY , 1f , 0f, 0f); float r = (float)(start.r)/255f; float g = (float)start.g/255f; float b = (float)start.b/255f; gl.glColor4f(r,g,b,1f); gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertices); for(int i = 0 ; i <5 ; i ++) { gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP,i*2,3); } gl.glFinish(); gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertices2); for(int i = 0 ; i <3 ; i ++) { gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP,i*3,3); } gl.glFinish(); if(start.dist>=maxDist) start.IsBigging = false; if(start.dist<=0) start.IsBigging = true; //此处的0.01f代表的是星星公转时候离心和向心运动的速度，即dist的变化速率
if(start.IsBigging) start.dist=start.dist + 0.01f; else start.dist=start.dist - 0.01f; rotateY = rotateY + start.rotateSelf; start.angle = start.angle +start.rotateElse; } }
