I'm happy to tell you that I just uploaded a fitted mesh body from MH to SL Betagrid. I hope I can remember all steps to get there eventually...
I used a female generic body with generic topology, exported as collada, disabled feet on ground, Z Up Face X, Meters. Disable smooth! It will mess up the weights later.
Imported it into a preloaded SL Basic Female blender file for fitted mesh ( SL wiki - Skeleton Female.blend - see below for link) using Blender 2.73.
I re-sized, relocated and rotated (2 degrees backwards) my body to be as close as the original BaseFemale on layer 1. Apply all transformations.
(We may have to edit the SL skeleton first now, have to move the tail of the eyes and prolly more to proper locations.)
I cleared the parent from the MH body totally and parented it to the SL skeleton using automatic weights, will be overridden below.
I selected all faces of the MH body, triangulated it.
Selecting the SL female body in object mode first, THEN then MH body as well, so transfer weights from SL Female to your MH body.
Test in Pose Mode. Rotate/grab some bones to see effects. Clear pose transformations after.
Export body and armature as collada with rigged preset for SL/opensim. I remember I didn't disable nor enabled options, use the preset and export at once.
Upload in SL without joint positions. I only uploaded as Highest LOD to test. Make all others 1.
Relog if needed, undeform avatar if needed. And use a new SL shape to test.
- This is only possible with Fitted Mesh. ;-)
I think that was my workflow. If not, sorry in advance. I need to reproduce all steps a few times first to get this done again. And for those who want to start at once: You NEED Blender experience and the
SL Base Skeletons for fitted mesh first.
Now, there is a lot to be done. Weighting can be better too but for a first experiment, the weights from the female base is ok. Just triangulate the MH body first. And make sure the skeleton fits to your own MH body precisely. At least the eyes have to move if you want to use your own SL system eyes. Also lowerlegs need a bit of work. Oh, and errr... bouncy boobs.
My 2 cents.