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I also had some other issues because of other modifers I had (the mesh was deforming weirdly) but I managed to fix it by simply applying the data transfer modifier. Open up Blender, go to File>User Preferences and press 'Install Add-On from File.' in the bottom bar.
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Right-click the folder called 'exportmdl' and go to Send To>Compressed Folder. Lastly, enter object mode > select your piece of clothing and then shift select your rig > CNTRL+P > with empty groups. Next, unzip it, and enter the folder so that you see the three files shown above. Now if you switch back to the object-data tab, there should be a listing of the bones of your armature under vertex groups. Finally press the generate data layers button at the bottom. Then, to make the tight clothing, select all of the surfaces you want to cover, and copy/paste them right on top of the model. Choose vertex data from the options and then select vertex groups. Easiest way Ive found to do that is simply load it up, put it in the T position, then export as a. Select the source from which you wish to copy the weights over (the main body). Now go to the modifers tab > add modifier > data transfer. So click on the object data tab and if there are any groups under vertex groups, delete them with the minus button on the side. Before you start, make sure you clear any vertex groups created when you parented the rig and unparent the item of clothing from the rig.
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Does anyone knows a source of avatar meshes with SL-compatible UVW- layout in the known formats like obj. But in several cases it would be much better to use a 3d paint program to create textures like deep paint or body paint. What you can do instead is use the data transfer modifier. I have already tried to make clothing with the templates in. For some reason, the weights do not transfer automatically in Blender 2.76 however it works perfectly in previous versions.
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