Introduction

Those who have tried adapting armor or clothing from one body type to another are very familiar with the phenomenon of clipping, in which parts of clothing or body parts stick through each other on movement in a way alien to both flesh and fabric. This can help you eliminate that. It can also be used to get instant vertex weights for your own custom projects from scratch, rather than having to set each vertex group's weight by hand (a tedious, time-consuming process).

Important Preliminaries:Your Modding Toolbox

To do this tutorial you will need:
The latest version of Blender, and a workingknowledge of the program. It's complicated.

3. NifSkope, a powerful mesh editor.

4. The Blender NIF scripts, which allow export of meshes from Blender in the right format for Oblivion. As of this writing I've achieved full functionality with Blender 2.45 plus the 2.21 NIF scripts and PyFFI 0.6.

Total Weight Paint Conversion

Open the file with your mesh in it in Blender 2.43 or later. Your mesh should already be at the origin in the middle of the view, but if not, make sure it is. If you've already done some weighting, I recommend deleting all rigging from your mesh first. This is best done in edit mode. Look for a little box that says "Bip01 Head" or another vert group name. Under it are buttons saying select, delete, deselect, et cetera. Click delete until all the vertex groups are gone. If you do that, save a new copy of your file in case of need. Import the .nif from which you want to copy the weights. Usually this will be a body file if you're making a mesh that shows skin, especially if you're doing it for a modded body. File - import - Netimmerse/Gamebryo. The two meshes should overlap. Don't move them.

Delete any skeletons from the scene now. You'll import another one to use for export later.

Go to edit mode. Select all vertices in your new mesh. Go back to object mode. Right Click on your new mesh. Now hold down shift and right click on the source mesh (the one you want to copy from).

Go to mesh - scripts - copy bone weights. A dialog pops up. Click the button that says "update selected." I use quality setting 3. You can use 4, but it takes longer and I haven't seen much of a difference in results.

Click the okay button.

Wait. This may be a long time depending on how good your CPU and memory are, especially with a higher-poly body mesh like Fantasy Figures (the one I usually work with). You can decrease this time by cutting unneeded polys from the body mesh - i.e. if you just want the lower legs, delete the thighs and pelvis in edit mode or separate them using the p key.
Your screen may show bizarre-looking spots or other artifacts during this process. Don't panic, it's normal.
When you can move anything on the screen again, SAVE your file right away. Then click on your mesh and go to weight paint mode in the dropdown that contains object mode and edit mode. You should see colors where everything was blue before. This means the script worked. You should also see the new vert groups in the edit mode dialogue where you originally deleted the old ones.

Delete the old mesh you copied from. Make sure you get its skeleton, too, in case you missed that earlier.

Delete the skeleton from your mesh and make sure your new mesh is highlighted. Now import a skeleton. I use the settings "realign bone tail roll" and "skeleton only, parent to selected." Reparent by right clicking your mesh and then the skeleton, then ctrl+p and choose "make parent to armature." Trust me, if you don't do this it's likely you'll get errors after export; Blender doesn't like it when you change weight paints on a mesh that's already parented and then exported as .nif. This was true with the old NIF scripts and it's so far apparentlytrue with the new ones, too.

Make sure you press ctrl-A before you export. ALWAYS ALWAYS ALWAYS PRESS CTRL A. DO NOT SKIP THIS. I am constantly getting questions from people who don't do this and thus get weird-looking meshes ingame.

Export and playtest. You're done!

Partial Weight Paint Converstion

This is somewhat more useful when you only want to change one vertex group or group of vertices to eliminate clipping. Do not delete any vertex groups from your mesh if you want to do this one. First, import the mesh you want to copy from. Leave it centered over your mesh. Select your mesh and go to edit mode. Select JUST the vertices you want to change weights on. I find the pelvic/thigh region interaction generally causes the most trouble for me with cuirass skirts and so on, so that's what I've selected in this picture. Go to object mode. Click first on your mesh, then click on the mesh from which you want to copy. Choose mesh -- scripts -- Bone weight copy. I use quality setting 3, but that's up to you. Press the "update selected" button BEFORE you click okay. This one may run very fast if you're only doing a few vertices. It's harder to tell if it worked, but you can usually see something like "vertex weights copied in .5504 seconds" if you bring up the little black Python window that's always running in the background when Blender is on. Export and playtest. The nice thing about this method is that it's much faster if you need to do repeated and more specialized tweaking.