To those having some problems with volume rendering - there is an issue in OR3 alpha 1 that causes it to use 3x as much memory during volume import. In some cases the Dragon VDB would work, but it would use an enormous amount of memory (effectively duplicating the volume 3 times). On my dev machine with 16GB mem I couldn't load it. This has been fixed and will be released with alpha 2. Thank you for your patience
Edit: I've been informed this is likely not the issue, we are investigating.