Hi.
You do not need to export your reference mesh in obj. Combine the body with the mesh at the very end. Make sure to rename uv map to uv_0 before combining it with the body.
If you're using MD8+, make sure to fix uvs before exporting the mesh
Do not close holes by extruding and scaling them down, extrude + scale + collapse ( Alt M - Collapse )
Why is your mesh vertex painted with blue
- ideally you should retopologize your garments after MD. If not, at least do not create them in tris. You also do not want it to be too dense, the final polycount of your whole garment+body should not go past 10-15k unless it is absolutely necessary which is not the case here;
- clone the dress, export its blend and name it Reference, open it;
- File - Save as the scene under whatever name you want, join all meshgroups, rename it to reference;
- File - Import - obj your MD mesh;
- unfold rig, make top visible and selectable, select it, in 3d view press Shift D, without moving cursor LMB-click to confirm, select top.001, Object - Parent - Clear Parent.
Remove unused vertex groups;
- switch to Edit mode (TAB), disable Limit selection to visible, select everything covered by your garment, press Delete and choose Faces;
- set
this as a background image for a uv_0 map, select everything with A, Shift-select your dress, rename UVMap to uv_0, switch to Edit mode, select everything in UV editor, set the same image, View - Draw other objects. In UV editor type in S Y 0.5 to shrink uvs back to they original size. Put everything in vacant places;
- close holes and add thickness with Mesh - Faces - Solidify if needed, unwrap added geometry right after you create it while it is still selected;
- transfer weights from the reference
- When transferring uv_1 map, use Nearest face interpolated option instead of the default one.
- vertex paint with 00FF00 and 3FFF00;
Vertex paint dictates what variation (skin-tight and robe-like) of deformation maps the painted area will deform according to in CAS during body customization and animation.
00FF00 is for skint-tight areas, 3FFF00 is for any skirt-like area ( skirts, bottom parts of dresses, coats, aprons, etc).
Start by choosing 00FF00 and Paint - Set vertex color
1). Disable Limit selection to visible;
2). Holding Ctrl, lasso-select the bottom part of the mesh starting somewhere in the middle of the pelvic bone;
3). Enable sync;
4). Press B and deselect legs;
5). Switch to Vertex paint and enable Face selection masking for painting;
6). Type in 3FFF00;
7). Paint - Set vertex colors;
8). Press A twice to deselect and select everything again, Paint - Smooth vertex colors
- only when you're done with weights, uv maps and vertex paint should you join the body and the dress;
- delete the reference, append it again. Rename meshgroups to ref + their cut numbers;
- split your mesh the same way the reference is by selecting the area and separating it with P - selection;
- after you split everything, remove unused vertex groups and add missing extra ones that the original have and yours does not;
- give them type and corresponding cut numbers, delete reference, save
I strongly advice you to postpone finishing this dress and instead watch more start-to-finish tutorials without following them. Once you have more or less decent understanding of what is going on, make the simplest skintight swimsuit or a top and try to make it perfect. Only after you succeed should you come back to this dress