Join objects and materials problem?

Hi,

I have imported an object from .3ds file and the object composed by 5 different meshes and two materials. I would like to join them together to one object. After join them together, it can be rendered in blender correctly. However, when I exported it to .sio2 and loaded it in simulator, only the first one materials was shown (entire object was covered by first materials).

Is there a way that SIO2 can handle two materials in one object? Thanks for your help.

Check on my youtube channel there's a video that show you how to use multimaterial on objects.

Thank you for quickly reply. I got it. Thanks once again.