Primitive objects in Carrara are not always as solid as they look. The mesh returned to Octane for a cube, for instance, is actually made up of six separate surfaces instead of a solid cube. In most situations this make little difference to the render. However, for rounded edges this makes all the difference in the world. Rounded edges only works when the edges are shared between surfaces.
To resolve this issue the plugin allows you to optimize the mesh of an object by sharing all vertices that are in the same location. By default all primitive objects are optimized, all other mesh objects are not.
Mesh optimization may not be appropriate in all cases. Sometimes you want hard edges and sometimes you don't. It is recommended that you only optimize mesh where you want to use edge rounding and the rounding is not working.
To enable mesh optimization on an object, select the object in the Assembly Room, select the Effects tab, and locate the Octane Object section. From there you can enable or disable mesh optimization.
Note: Optimizing very large meshes can significantly affect the load time of the mesh into Octane. This may be of particular concern when animating the mesh in question.