Please forgive this extremely basic question. I am new to 3d graphics and have been using Milkshape, but want to move on to Blender.
I want to import a wavefront obj file which I exported from Plantstudio into Blender 2.42a in such a way that I retain the group information. Once in Blender, I want to merge some of the small groups into larger groups because they can all use the same texture or material.
I have been able to import it so that the groups end up as separate datablocks. However, I am not sure how to assign the individual datablocks (there are many) to groups efficiently - it seems that I can only select one datablock at a time and this is done in a very roundabout way.
Is there a way of importing an obj file in such a way that the groups in the obj file end up as groups in Blender? I have been trying various options on the Obj import dialog, but I can’t get it to work. Which of the options should I choose?
I would so appreciate help with this - I have been struggling for days.
When you import your obj, deselect the Split by Objects, Split by Group, and Split by Material options in the Import dialogue. Your objects will be assigned individual materials and joined as a single mesh.
Blender only supports 16 materials per mesh so if your model has more than 16 materials they will be truncated.
If you import a model with seperated meshes, for instance a model that has more than 16 materials, you can select each individual mesh [shift-click and/or B-key border select] and combine them with Ctrl-J. This will give you a single mesh with individual materials (you can select by material in the edit tools).
Grouping is a different beast in blender, but is accomplished with Ctrl-G and is used for things like hair and other advanced features.
If you want to control several individual items simultaneously, but still want to retain seperate meshes you can parent meshes to an Empty. This allows to control position location etc. and coincidentally makes for a cleaner outliner display.
Going the other way, assinging a material to several meshes while keeping the meshes seperate, you’d want to select all the meshes that are to be assigned the new material and then lastly select the mesh with material that is to be used and type Ctrl-L, material. That’ll assign the material of the last selected mesh to all the selected meshes.
That help? 
Thank you so much. I did exactly as you advised, but my imported object has no assigned vertex groups. It does however, have almost 150 different datablocks when I open the data browser, and those correspond to the groups in my original obj file. In Blender they each seem to be a different mesh. Visually selecting the different mesh parts with border select is difficult due to the complex form of the plant - the leaves are easy to see but the stems and stalks are not. I can select each datablock from the data browser and assign its vertices to a group, but that involves going back and forth between edit and object mode and several keypresses each time - not an efficient process at all. When I import the same obj file into Milkshape, all the groups are there, as groups, very easily accessible - I just pick them off a list. From what I have been reading in the tutorials and manual, Blender does indeed seem to treat groups as a different concept from what I am used to. I am beginning to realise that each package has its strengths and limitations. I think for this particular task, using an imported plant, I am better off using Milkshape. For my next plant I am going to try and create it in Blender from scratch so that I can use the method you have described.
Seems like complexity is the nature of computer graphics, doesn’t it? I’m sorry to hear you haven’t found a solution.
I’ve been importing flowers into blender recently and have been able to manage a reasonably simple approach although the imported objects only had about a dozen material regions or so.
If I need to pick an object from an alphabetical list I use the Outliner. The Outliner is found by clicking on the header’s header type drop down, usually found at the bottom of the editing window as a default. The outliner will give you a complete list of all the meshes and various objects in your scene.
You can split the windows and have the Outliner open at the same time you’re working on the meshes as well.
I still think you may be able to achieve a blender solution by trying different obj import options, but it’s difficult to say without actually seeing the meshes you’re working with.