OpenGL绘制棱锥,剔除

/**
 * 缓冲区工具类
 */
public class BufferUtil {
 /**
  * 将浮点数组转换成字节缓冲区
  */
 public static ByteBuffer arr2ByteBuffer(float[] arr){
  ByteBuffer ibb = ByteBuffer.allocateDirect(arr.length * 4);
  ibb.order(ByteOrder.nativeOrder());
  FloatBuffer fbb = ibb.asFloatBuffer();
  fbb.put(arr);
  ibb.position(0);
  return ibb ;
 }
 
 /**
  * 将list转换成字节缓冲区
  */
 public static ByteBuffer list2ByteBuffer(List<Float> list){
  ByteBuffer ibb = ByteBuffer.allocateDirect(list.size() * 4);
  ibb.order(ByteOrder.nativeOrder());
  FloatBuffer fbb = ibb.asFloatBuffer();
  for(Float f : list){
   fbb.put(f);
  }
  ibb.position(0);
  return ibb ;
 }
}

/**

* 渲染器

*/

public abstract class AbstractMyRenderer implements android.opengl.GLSurfaceView.Renderer

{

private float ratio;

public float xrotate = 0f;//围绕x轴旋转角度

public float yrotate = 0f;//围绕x轴旋转角度

/**

* 1.

*/

public void onSurfaceCreated(GL10 gl, EGLConfig config)

{

//清平色

gl.glClearColor(0f, 0f, 0f, 1f);

//启用顶点缓冲区数组

gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);

}

/**

* 2.

*/

public void onSurfaceChanged(GL10 gl, int width, int height) {

//设置视口

gl.glViewport(0, 0, width, height);

ratio = (float)width / (float)height;

//投影矩阵

gl.glMatrixMode(GL10.GL_PROJECTION);

//加载单位矩阵

gl.glLoadIdentity();

//设置平截头体

gl.glFrustumf(-ratio, ratio, -1, 1, 3f, 7f);  }

/**

* 3.

*/

public abstract void onDrawFrame(GL10 gl);

}

**

* 棱锥,正方形

*/

public class MyTriangleConeRenderer extends AbstractMyRenderer{

public void onSurfaceCreated(GL10 gl, EGLConfig config) {

gl.glClearColor(0f, 0f, 0f, 1f);
  //顶点缓冲区
  gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
  //启用颜色缓冲区
  gl.glEnableClientState(GL10.GL_COLOR_ARRAY);
 }
 
 public void onDrawFrame(GL10 gl) {
  //清除颜色缓冲区和深度缓冲区
  gl.glClear(GL10.GL_COLOR_BUFFER_BIT|GL10.GL_DEPTH_BUFFER_BIT);
  //设置绘图颜色
  gl.glColor4f(1f, 0f, 0f, 1f);
  
  //启用深度测试
  gl.glEnable(GL10.GL_DEPTH_TEST);
  
  //启用表面剔除
  gl.glEnable(GL10.GL_CULL_FACE);
  //指定前面()
  //ccw:counter clock wise-->逆时针
  //cw:clock wise--> 顺时针
  gl.glFrontFace(GL10.GL_CCW);
  //剔除背面
  gl.glCullFace(GL10.GL_BACK);
  
  //GL10.GL_SMOOTH:平滑着色(默认)
  //GL10.GL_FLAT:单调模式
  gl.glShadeModel(GL10.GL_FLAT);
  
  //操作模型视图矩阵
  gl.glMatrixMode(GL10.GL_MODELVIEW);
  gl.glLoadIdentity();
  //设置眼球的参数
  GLU.gluLookAt(gl,0f,0f,5f, 0f, 0f, 0f, 0f,1f,0f);
  
  //旋转角度
  gl.glRotatef(xrotate, 1, 0, 0);
  gl.glRotatef(yrotate, 0, 1, 0);
  
  //计算点坐标
  float r = 0.5f ;//半径
  float x = 0f,y = 0f,z = -0.5f ;
  
  /******************** 锥面 ************************/
  //顶点坐标集合
  List<Float> coordsList = new ArrayList<Float>();
  //添加锥顶点
  coordsList.add(0f);
  coordsList.add(0f);
  coordsList.add(0.5f);
  
  //顶点颜色集合
  List<Float> colorList = new ArrayList<Float>();
  colorList.add(1f);//r
  colorList.add(0f);//g
  colorList.add(0f);//b
  colorList.add(1f);//a
  
  /******************** 锥底 ************************/
  //锥底坐标
  List<Float> coordsConeBottomList = new ArrayList<Float>();
  coordsConeBottomList.add(0f);
  coordsConeBottomList.add(0f);
  coordsConeBottomList.add(-0.5f);
  
  boolean flag = false ;
  //底面
  for(float alpha = 0f ; alpha < Math.PI * 6 ; alpha = (float) (alpha + Math.PI / 8)){
   //锥面
   x = (float) (r * Math.cos(alpha));
   y = (float) (r * Math.sin(alpha));
   coordsList.add(x);
   coordsList.add(y);
   coordsList.add(z);
   
   //锥底坐标
   coordsConeBottomList.add(x);
   coordsConeBottomList.add(y);
   coordsConeBottomList.add(z);
   
   //点颜色值
   if(flag = !flag){
    //黄色
    colorList.add(1f);
    colorList.add(1f);
    colorList.add(0f);
    colorList.add(1f);
   }
   else{
    //红色
    colorList.add(1f);
    colorList.add(0f);
    colorList.add(0f);
    colorList.add(1f);
   }
  }
  //点颜色值
  if(flag = !flag){
   //黄色
   colorList.add(1f);
   colorList.add(1f);
   colorList.add(0f);
   colorList.add(1f);
  }
  else{
   //红色
   colorList.add(1f);
   colorList.add(0f);
   colorList.add(0f);
   colorList.add(1f);
  }
  
  //颜色缓冲区
  ByteBuffer colorBuffer = BufferUtil.list2ByteBuffer(colorList);
  gl.glColorPointer(4, GL10.GL_FLOAT, 0, colorBuffer);
  //绘制锥面
  gl.glVertexPointer(3, GL10.GL_FLOAT, 0, BufferUtil.list2ByteBuffer(coordsList));
  gl.glDrawArrays(GL10.GL_TRIANGLE_FAN, 0, coordsList.size() / 3);
  
  //剔除正面
  gl.glCullFace(GL10.GL_FRONT);
  //绘制锥底
  colorBuffer.position(4);
  gl.glColorPointer(4, GL10.GL_FLOAT, 0, colorBuffer);
  gl.glVertexPointer(3, GL10.GL_FLOAT, 0, BufferUtil.list2ByteBuffer(coordsConeBottomList));
  gl.glDrawArrays(GL10.GL_TRIANGLE_FAN, 0, coordsConeBottomList.size() / 3);
 }
}

//主界面

public class MainActivity extends Activity {

private AbstractMyRenderer render;

private MyGLSurfaceView view;

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

view = new GLSurfaceView(this);

render = new MyTriangleConeRenderer();

view.setRenderer(render);

//GLSurfaceView.RENDERMODE_CONTINUOUSLY:持续渲染(默认)

//GLSurfaceView.RENDERMODE_WHEN_DIRTY:脏渲染,命令渲染

view.setRenderMode(GLSurfaceView.RENDERMODE_WHEN_DIRTY);

setContentView(view);

}

public boolean onKeyDown(int keyCode, KeyEvent event) {

float step = 5f ;

//up

if(keyCode == KeyEvent.KEYCODE_DPAD_UP){

render.xrotate = render.xrotate - step ;

}      else if(keyCode == KeyEvent.KEYCODE_DPAD_DOWN){

render.xrotate = render.xrotate + step ;

}      else if(keyCode == KeyEvent.KEYCODE_DPAD_LEFT){

render.yrotate = render.yrotate + step ;

}      else if(keyCode == KeyEvent.KEYCODE_DPAD_RIGHT){

render.yrotate = render.yrotate - step ;

}

//请求渲染,和脏渲染配合使用

view.requestRender();

return super.onKeyDown(keyCode, event);

}

}