irr::scene::SMesh *dmes = new irr::scene::SMesh;

irr::scene::SMeshBuffer *buffer = new irr::scene::SMeshBuffer;
buffer->recalculateBoundingBox();
dmes->addMeshBuffer(buffer);
buffer->drop();

SMeshBuffer* buf = (SMeshBuffer*)smgr->getMesh("data/grass.obj")->getMeshBuffer(0);
buf->recalculateBoundingBox();
dmes->addMeshBuffer(buf);
buf->drop();

cout << dmes->getMeshBufferCount() << " **********" << endl;

IMeshSceneNode* myNode = smgr->addMeshSceneNode(dmes);
myNode->setMaterialFlag(EMF_LIGHTING, false);
myNode->setScale(vector3df(10));
myNode->setMaterialType(EMT_TRANSPARENT_ALPHA_CHANNEL);