question: @ Override public void onDrawFrame ( GL10 gl10 ) { GLES20 . glClearColor ( 1.0f , 0.0f , 0.0f , 1.0f ) ; GLES20 . glClear ( GLES20 . GL_COLOR_BUFFER_BIT | GLES20 . GL_DEPTH_BUFFER_BIT ) ; GLES20 . glEnable ( GLES20 . GL_DEPTH_TEST ) ; GLES20 . glEnable ( GLES20 . GL_CULL_FACE ) ; long currentTimeMillis = System . currentTimeMillis ( ) ; updateWithDelta ( currentTimeMillis - lastTimeMillis ) ; lastTimeMillis = currentTimeMillis ; }
target:  GLSurfaceView has default 16bit depth buffer