Official Granny 3D Viewer:
http://www.radgametools.com/granny/download.html

This is usefull to take a look at the .gr2 files that contain the 3D models. It only works for very few though, namely all resource tile models (eg. aluminium.gr2, superhorses.gr2, resource_*.gr2, etc.). I found it still useful, it gives some infos about what exactly is in the files, which is handy when trying around with the material editor.

The Importer/Exporter (with sourcecode!) can be found here:
http://gr2decode.altervista.org/download.html

sadly only for 3dsmax2008, which I don't own, but there is sourcecode also, which should make it possible to compile a Plugin for GMAX or even write a standalone converter from scratch.

Great to know about the importer/exporter, I'll try that later but almost certain it won't handle Civ5 original gr2's.. if you try there you'll see that neither Granny Viewer import them, since Firaxis modified the format their way - not a very mod-friendly move if you ask me, but I'm hopeful that they'll release some plugins for us.

Great to know about the importer/exporter, I'll try that later but almost certain it won't handle Civ5 original gr2's.. if you try there you'll see that neither Granny Viewer import them, since Firaxis modified the format their way - not a very mod-friendly move if you ask me, but I'm hopeful that they'll release some plugins for us.

That is not true for all models, a lot of the tile resources will show up in the granny viewer. So hopefully the importer/exporter will work for those too.