OpenGL繪製稜錐,剔除

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/**
 * 緩衝區工具類
 */
public class BufferUtil {
 /**
  * 將浮點數群組轉換成位元組緩衝區
  */
 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 ;
 }
 
 /**
  * 將list轉換成位元組緩衝區
  */
 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;//圍繞x軸旋轉角度

public float yrotate = 0f;//圍繞x軸旋轉角度  

 /**

  * 1.

  */  

public void onSurfaceCreated(GL10 gl, EGLConfig config)

{  

 //清平色  

 gl.glClearColor(0f, 0f, 0f, 1f);   

//啟用頂點緩衝區數組

  gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);  

}

/**  

* 2.

  */

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

//設定視口

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

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

//投影矩陣  

 gl.glMatrixMode(GL10.GL_PROJECTION);

  //載入單位矩陣  

 gl.glLoadIdentity();  

 //設定平截頭體   

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

/**

  * 3.

  */  

public abstract void onDrawFrame(GL10 gl);

}

 

**  

* 稜錐,正方形  

*/

public class MyTriangleConeRenderer extends AbstractMyRenderer{

 public void onSurfaceCreated(GL10 gl, EGLConfig config) {

gl.glClearColor(0f, 0f, 0f, 1f);
  //頂點緩衝區
  gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
  //啟用顏色緩衝區
  gl.glEnableClientState(GL10.GL_COLOR_ARRAY);
 }
 
 public void onDrawFrame(GL10 gl) {
  //清除顏色緩衝區和深度緩衝區
  gl.glClear(GL10.GL_COLOR_BUFFER_BIT|GL10.GL_DEPTH_BUFFER_BIT);
  //設定繪圖顏色
  gl.glColor4f(1f, 0f, 0f, 1f);
  
  //啟用深度測試
  gl.glEnable(GL10.GL_DEPTH_TEST);
  
  //啟用表面剔除
  gl.glEnable(GL10.GL_CULL_FACE);
  //指定前面()
  //ccw:counter clock wise-->逆時針
  //cw:clock wise--> 順時針
  gl.glFrontFace(GL10.GL_CCW);
  //剔除背面
  gl.glCullFace(GL10.GL_BACK);
  
  //GL10.GL_SMOOTH:平滑著色(預設)
  //GL10.GL_FLAT:單調模式
  gl.glShadeModel(GL10.GL_FLAT);
  
  //操作模型視圖矩陣
  gl.glMatrixMode(GL10.GL_MODELVIEW);
  gl.glLoadIdentity();
  //設定眼球的參數
  GLU.gluLookAt(gl,0f,0f,5f, 0f, 0f, 0f, 0f,1f,0f);
  
  //旋轉角度
  gl.glRotatef(xrotate, 1, 0, 0);
  gl.glRotatef(yrotate, 0, 1, 0);
  
  //計算點座標
  float r = 0.5f ;//半徑
  float x = 0f,y = 0f,z = -0.5f ;
  
  /******************** 錐面 ************************/
  //頂點座標集合
  List<Float> coordsList = new ArrayList<Float>();
  //添加錐頂點
  coordsList.add(0f);
  coordsList.add(0f);
  coordsList.add(0.5f);
  
  //頂點顏色集合
  List<Float> colorList = new ArrayList<Float>();
  colorList.add(1f);//r
  colorList.add(0f);//g
  colorList.add(0f);//b
  colorList.add(1f);//a
  
  /******************** 錐底 ************************/
  //錐底座標
  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)){
   //錐面
   x = (float) (r * Math.cos(alpha));
   y = (float) (r * Math.sin(alpha));
   coordsList.add(x);
   coordsList.add(y);
   coordsList.add(z);
   
   //錐底座標
   coordsConeBottomList.add(x);
   coordsConeBottomList.add(y);
   coordsConeBottomList.add(z);
   
   //點顏色值
   if(flag = !flag){
    //黃色
    colorList.add(1f);
    colorList.add(1f);
    colorList.add(0f);
    colorList.add(1f);
   }
   else{
    //紅色
    colorList.add(1f);
    colorList.add(0f);
    colorList.add(0f);
    colorList.add(1f);
   }
  }
  //點顏色值
  if(flag = !flag){
   //黃色
   colorList.add(1f);
   colorList.add(1f);
   colorList.add(0f);
   colorList.add(1f);
  }
  else{
   //紅色
   colorList.add(1f);
   colorList.add(0f);
   colorList.add(0f);
   colorList.add(1f);
  }
  
  //顏色緩衝區
  ByteBuffer colorBuffer = BufferUtil.list2ByteBuffer(colorList);
  gl.glColorPointer(4, GL10.GL_FLOAT, 0, colorBuffer);
  //繪製錐面
  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);
  //繪製錐底
  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);
 }
}

//主介面

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:持續渲染(預設)        

//GLSurfaceView.RENDERMODE_WHEN_DIRTY:髒渲染,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 ;    

 }      

//請求渲染,和髒渲染配合使用      

view.requestRender();    

 return super.onKeyDown(keyCode, event);    

}

}