title: Is it possible to in-place resize VBOs?
body: <p>The title says everything, but just to be clear I'll add some extra words.</p>
  
  <p>In this case, <em>resize</em> means: </p>
  
  <ul>
  <li>getting more storage space at the end of the old vbo</li>
  <li>saving the old data at the front</li>
  <li>(hopefully not copying, but at least not on CPU side, meaning the driver should handle this)</li>
  </ul>
  
  <p><strong>EDIT</strong></p>
  
  <p>As to explain some more details and justify my question:<br/>
  I will store data of (in forehand) unknown size to the VBO but I only know an upper limit that is a very rough estimation (10 - 100x as much or even more in unusual conditions).</p>
  
  <p>Of course I know how much data I stored, when I am done with it, so it would be nice to store data until I find my VBO too small and resize it and then go on storing.</p>
  
  <p>Here is why I don't want to copy(especially not on CPU side):<br/>
  I am doing all this on the GPU to get interactive frame rates. When I have to copy it is very slow or even not possible, because there is not enough space. Worst of all is to copy the data over the CPU, hence passing everything over the bus, into a new memory region that has sufficient size, then <code>glBufferData</code>ing the VBO with new size and the new memory region as source. That would be the performance killer.</p>
  
  <p><strong>circumvented</strong></p>
  
  <p>I circumvented the problem with an exact estimation of the needed space. But I will let this question be unanswered for a week to see if someone has another hint on this as I am not very happy with the solution.</p>