Vertex groups for a backpack

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Vertex groups for a backpack

Postby janexx » Wed Mar 31, 2021 11:51 pm

Hi there,

I created a schoolbag (http://www.makehumancommunity.org/clothes/schoolbag_for_boys.html) in Blender (my second cloth asset for makehuman) and was able to upload it here with the MakeClothes2 Plugin. I followed some older post where someone made something similar and created the vertex groups like here ( http://www.makehumancommunity.org/forum/viewtopic.php?f=6&t=13382#p34272 ) described:

For the "pack" itself create a special vertex group where the name begins with a ' * ' On the backpack side it contains all the vertices of the bag and on the human model side it contains only three (! this is important !) vertices, in form of an isosceles triangle on the human back. For the belt of the backpack use normal vertex groups.


What worked for me since now is to assign just one group called *bag to all bag vertices. It looks good in Makehuman, but then the bag is not really skinned to the human model. Now I wanted to skin it and find it really difficult to weightpaint the belts / assign vertex groups because every vertex must belong to only one vertex group. Using the automatic weight function in Blender doesn't help here very much. When I finally created the cloth (by hitting the "Make clothes" button in the addon) the mesh is totally exploded in Makehuman. Is there a trick how I can do that best?
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Re: Vertex groups for a backpack

Postby punkduck » Sun Apr 04, 2021 8:03 pm

janexx wrote:Hi there,


For the "pack" itself create a special vertex group where the name begins with a ' * ' On the backpack side it contains all the vertices of the bag and on the human model side it contains only three (! this is important !) vertices, in form of an isosceles triangle on the human back. For the belt of the backpack use normal vertex groups.



Well the asterisk never meant anything ... since each vertex is calculated by the nearest 3 "available" vertices, it didn't matter if a '*' was in front of the name when only 3 were given ;)

That's the reason I didn't continue the old way of MakeClothes and did not mention it explicitely in the new Version. However the documentation is describing the same:


http://www.makehumancommunity.org/wiki/Documentation:ClothesV2

From there I linked to create vertex groups:

http://www.makehumancommunity.org/wiki/Documentation:MakeClothes_Vertex-Groups

The crown is an element with 3 reference vertices and should also not bend. Of course it will adapt to the size of the head whereas your bag also grows with the character ... ( and might be higher for a tall character)


janexx wrote:What worked for me since now is to assign just one group called *bag to all bag vertices. It looks good in Makehuman, but then the bag is not really skinned to the human model. Now I wanted to skin it and find it really difficult to weightpaint the belts / assign vertex groups because every vertex must belong to only one vertex group. Using the automatic weight function in Blender doesn't help here very much. When I finally created the cloth (by hitting the "Make clothes" button in the addon) the mesh is totally exploded in Makehuman. Is there a trick how I can do that best?


Inside MakeHuman we use both, vertex groups which adapt to the body (the straps in your case) and some which don't do it (the bag itself). The problem is the boundary between both. So this problem is normally solved with two vertexgroups, straps are assigned to a non-rigid group, (I would use part of tight-helper normally) and bag would use 3 vertices on the back.

Best result is when the straps end near one of the 3 verts for the bag, I guess.

This method is partly used for e.g. the wonder-woman strap I did, but also for buttons and buckles. Also for the diver equipment Grinsegold did with me. The diving cylinder isn't that flexible in reality :mrgreen:

However, the method will never be perfect. If in Blender an exported mesh from MakeHuman sometimes must be corrected, worst results are typically for females with different breast sizes because formerly rigid buttons are squeezed to ovals etc. On other parts smoothing of the weights might help. The buttons must be usually created again.

The most perfect way: It is possible to export own weights from Blender to MakeHuman. If you want to take a look: The standard shoes come with a .mhw file. These are weights like for the standard body itself. But this means a weight transfer (+ weight painting) in Blender and then export the .mhw file.

First try with the "normal" method, so doing a group for straps and one for the bag.

I can of course add a tutorial how to create an .mhw file somewhen. It is blender work + exporting with a plugin.
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Re: Vertex groups for a backpack

Postby janexx » Tue Apr 20, 2021 9:16 pm

Thanks for your reply!

When I understand you right, I need two vertex groups: 1) for the bag which is fully assigned to this one vertex group and 2) for the straps which should be assigned to a non-rigid group

But I don't know how to assign the vertices of the straps. When I assign all vertices of the straps to the group "straps" and also have some weight painting to other vertex groups (like spine, clavicle) I get the error which says that I can not assign a vertex to multiple vertex groups. I also don't know how I would use the weights of the helper geometry like form the Tights. What could be a good approach? Or did I understand something wrong?
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Re: Vertex groups for a backpack

Postby Elvaerwyn » Tue Apr 20, 2021 9:44 pm

Maybe a silly question but did you make sure to delete all of the vertex associations on the straps prior to associating them with the new vertex group you made? Blender can be a tad tricky when associating and de associating, make sure all of the vertexes are selected before clicking remove vertexes button. And to be sure i often times click the assign button numerous times, as in old blender there was a bug I noticed where it missed the assign sometimes!
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Re: Vertex groups for a backpack

Postby janexx » Wed Apr 21, 2021 10:44 pm

Ehm no, I have vertices applied to multiple vertex groups. I thought it is possible to skin / weightpaint the straps of the backpack? Should the vertices of the straps only be applied to the "straps" group and no others? But then the straps would not be associated with e.g. the vertex groups of the shoulders and therefore not move with the bones / body parts. Honestly I don't understand the workflow.
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