How to merge 2, 3, ..., n mesh into one?

I have some mesh as:

now, if I want to merge 2 mesh into one, so viewer can understand that is only one node. I have to merge all infomation (float_array, material, texture, index vertex) or only need to merge instance like this?

<node id="VisualSceneNode2" type="NODE">
      <instance_geometry url="#geoid1"/>
<instance_geometry url="#geoid2"/>
<instance_geometry url="#geoid3"/>


I’m trying to merge 2 mesh by merging vertex. In the classe FCDGeometrySource, there is a function SetData, the input is a FloatList, but there is no Get function which return a FloatList at the FCDGeometrySource, that’s strange.