I just exported another and it did not save the groups. Is there a simple way to preserve groups from an OBJ file when exporting it out as XSI?
Yes, but you will have to do several things in XSI first. Its kinda hard for me to explain so bear with me, and it would be a good idea to go over the section in the documentation of the forge tools "Modding_XSItoSins_ModdingSupplement" and read over the advanced section at the bottom of the page. Also read the "Note;" on steps 1 and 3 first, before you go through each step.
If you are where I think your at and it looks like this in your scene root explorer pop up (8 on key board) but all your materials have the same name under each mesh cluster;
1.Then you must ensure that each group( you mean cluster in xsi, yes? ) has its own individually named material. Go to "Get" > materials > assign material" then pick a mesh within your explorer under Cluster, it should have its own name when it is assigned. Then delete the old 1 ( you will need to go to the materials section of the explorer; press "m" with your cursor is over the explorer and delete the old materials from there also). Then you will have to hook up all the relevant texture files to each material for each cluster within the render tree(7 on key board). You may only need to do this to the clusters you assigned new materials.
Note;If each cluster's material is already different forget this first step you are good to go on with the next step.
2. Then you will have to give your model tangents. Select the whole polymsh and follow the instructions in the documentation on assigning tangents
3. You will have to put in the rootpoint and all the nulls you want also as Obj.'s cannot transfer this information either.
Note; if you can, use .Fbx. Fbx can contain more info than Obj.
If on the other hand your groups are still individual polymsh1, polymsh2 etc. and are situated straight under the light, rootpoint etc., you have a bit more of a process to go through and you must merge them all to 1 polymsh first. De-select all then Go to "Create" > "Poly.Mesh"> "Merge" and pick the mesh's to be merged, then right click. In the pop up press merge button just under "Material, UV's, VertexColors, WieghtMaps". then press "Delete" button. You should now have the different Polymsh's as Clusters. Then follow steps 1,2 & 3.
PS. sorry if it is a little unclear, I am not so good at explaining things and I assume you Know your way around xsi somewhat and differences in terminology always makes things hard.
Also I don't know why, but the Quote I did from your post Siniperium has it as from Stant123 I don't know how this is possible. Perhaps the web guy needs to take a look at it.
Edit; I forgot to mention it is ok! and in fact ideal if the top cluster -New_Mesh in the picture shares the same material as the material in the (Scene_Root) as shown on the very bottom line in the picture. The little round purple icons for them have 2 ticks on them to confirm this.