title: how to assign one texture to another efficiently in OpenGL ES for Android
body: <p>I want to copy texture1 to texture2. The background is that I generate 15 empty texture id and bind them to <code>GLES11Ext.GL_TEXTURE_EXTERNAL_OES</code>, the following is my code:</p>
  
  <pre><code>int[] textures = new int[15];
  GLES20.glGenTextures(15, textures, 0);
  GlUtil.checkGlError("glGenTextures");
  
  for(int i=0;i&lt;15;i++)
      GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, textures[i]);
  </code></pre>
  
  <p>then I always transfer camera preview to <code>textures[0]</code>, I want copy the texture from <code>textures[0]</code> to <code>textures[1]</code> in order to keep the frame content of timestamp 1, and copy the texture from <code>textures[0]</code> to <code>textures[2]</code> in order to keep the frame content of timestamp 2... it looks like buffer some texture data in GPU and render some of that in the future.  So I want to know is there anyway to do this? And can I just use <code>textures[2]=textures[0]</code> to copy texture data?</p>