openGL剪裁區

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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 ;
 }
}

 

/**
 * 剪裁區
 */
public class MyScissorRenderer extends AbstractMyRenderer{

private int width ;
 private int height ;
 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);
 }
 
 public void onSurfaceChanged(GL10 gl, int width, int height) {
  this.width = width ;
  this.height = height ;
  
  gl.glViewport(0, 0, width, height);
  ratio = (float)width / (float)height;
  gl.glMatrixMode(GL10.GL_PROJECTION);
  gl.glLoadIdentity();
  gl.glFrustumf(-ratio, ratio, -1, 1, 3f, 7f);
 }
 
 public void onDrawFrame(GL10 gl) {
  gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
  gl.glColor4f(1f, 0f, 0f, 1f);
  
  //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);
  
  //啟用剪裁
  gl.glEnable(GL10.GL_SCISSOR_TEST);
  
  //旋轉角度
  gl.glRotatef(xrotate, 1, 0, 0);
  gl.glRotatef(yrotate, 0, 1, 0);
  
  float[] coords = {
   -ratio,1f,2f ,
   -ratio,-1f,2f ,
   ratio,1f,2f ,
   ratio,-1f,2f
  };
  
  //顏色數組
  float[][] colors = {
    {1f,0f,0f,1f},
    {0f,1f,0f,1f},
    {0f,0f,1f,1f},
    {1f,1f,0f,1f},
    {0f,1f,1f,1f},
    {1f,0f,1f,1f},
  };
  
  int step = 20 ;
  for(int i = 0 ; i < 6 ; i ++){
   //設定剪裁區
   gl.glScissor(i * 20, i * 20, width - (i * 20 * 2), height - (i * 20 * 2));
   //設定顏色
   gl.glColor4f(colors[i][0],colors[i][1],colors[i][2],colors[i][3]);
   gl.glVertexPointer(3, GL10.GL_FLOAT, 0, BufferUtil.arr2ByteBuffer(coords));
   gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 0, 4);
  }
 }
}

 

//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 MyTriangleRenderer();        

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);    

}

}