I think I read, when MW1.6 was released, that to make sure that instancing worked it was better if the geometry was collapsed into a editable mesh.
That's a handy trick if you're using File Link Mechanism or working with imported geometry from Revit/Autocad and friends.
Scatter modifier doesn't work with instancing as explained
here. You can use Crowd modifier instead.
Will any kind of object work (compound objects, parametric, groups...)?
Groups are working, compound object are not (at least Scatter), parametric I don't have a clue.
Now, I'm wondering if all instances should be editable meshes or poly as a base object and if can add over it any kind of modifier as, for example, taper, bend, FFD box, noise, optimize or multires. Will any of those cause some trouble?
No, not every object should be an editable mesh, and yes, you can use bend, optimize etc.
The easiest way to check if the scene/object you're working is exported using instancing, is to check the number of meshes reported by MXCL.
This picture was made of a Tube and a bend modifier, and the numbers when using instancing:
Geometry:
- Num Meshes: 1
- Num Triangles: 432
- Num Vertexes: 216
- Num Normals: 288
and the number with normal geometry:
Geometry:
- Num Meshes: 404
- Num Triangles: 174528
- Num Vertexes: 87264
- Num Normals: 116352