There appears to be a bug in the wrapping process with ManualObject, and likely elsewhere. According to http://www.ogre3d.org/docs/api/html/classOgre_1_1ManualObject.html#573c1c83b42950a7c040f833236c6531 the manualObject.Triangle() and manualObject.Index() (and maybe some more) should take uint32 not unint numbers as parameters. Effectively this reduces the number of vertices you can add to a manual object to 65 thousand rather than 4 Million. The comments in the Mogre version also suggest that it should be uint32. I'm using Mogre 1.6.5.