title: GPU Manual Mipmap Generation [OpenGL 2.x]
body: <p>i want use a specific customized algorithm to generate mipmaps for some renderable textures (R16F &amp; RGBA16F).</p>
  
  <p>All needed textures' mipmaps are pre-enabled by using glGenerateMipmapEXT().</p>
  
  <p>The biggest problem so far is to render into 1+ mipmap levels.
  <strong>More precisely,
  this works like a charm:</strong></p>
  
  <pre><code>...
  glDrawBuffer(GL_COLOR_ATTACHMENT0_EXT);
  glFramebufferTexture2DEXT( GL_FRAMEBUFFER_EXT, target, texType, texId, 0 );
  checkFBOStatus();
  ...
  render();
  </code></pre>
  
  <p><strong>But this gives me a GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT_EXT when checking fbo status</strong></p>
  
  <pre><code>...
  glDrawBuffer(GL_COLOR_ATTACHMENT0_EXT);
  glFramebufferTexture2DEXT( GL_FRAMEBUFFER_EXT, target, texType, texId, 1 );
  checkFBOStatus();
  ...
  render();
  </code></pre>
  
  <p><strong><em>All the difference in code is the lod level parameter for attaching a texture onto the FBO.</em></strong></p>
  
  <p>after lots of feverish head-scratching, i still cant get it work.
  So, any answer is greatly appreciated.</p>
  
  <p>[NOTE: target platform is OpenGL 2.x with FBO extension]</p>