I finally wrote an exporter for blender to directly export a selected object to my engines custom file format. "Only" thing missing for the exporter are animations, which aren´t exported yet.
I btw put the engine on Indie DB:
http://www.indiedb.com/engines/isdgeI have no idea what I did there, but so far all models exported with it worked fine
. It also supports several textures per object.