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Weight painting for skirts / dresses


Sharie Criss
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Using latest Blender and Avastar, I've created a simple dress going through Gaia's awesome video series. When the dress is created, it's shrinkwrapped to the SL Avatar skirt mesh, and when rigged the weight copy gets taked my guess mainly from that SL skirt. Now as we all know, and the video shows, the SL skirt has TERRIBLE weights, resulting in the nasty sheering between the legs, and the hard crease that badly distorts at the top of the hip.


In the video, the weight painting tools make things a little better, but it never goes into deep detail about selecting different weight groups and the weighting tools. My result is that things get worse, not better! I "get it" that certain bones should have more influence over how a vertex moves than others, and I understand the color system blender uses during weight painting. What I don't get is how many dresses I buy the rigging is just totally awesome for moving those upper leg bones, the mesh remains smooth and stretches naturally. Question is, How do they do that?!! Are they not using blender? Not starting with the dress rigged to the SL skirt weights? Are there more controlled ways of editing the mesh weights than weight painting?

http://gyazo.com/1dd063a6ec0cbb3754dfd14dc6422a6e

 

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Point us to some of the skirts you see as handling the skirt stretch well.

The Linden system skirt has stretch problems. User made skirts that I've seen also have stretch problems. Whether one uses the LL skirt or lowerbody weighting it is a problem.

I have seen some try changing the UVMap to make the stretch distortion less noticable. But, that then introduces compression distortion when the avatar is in a stand pose.

The basic problem is a very small area of the skirt along the front view center line is stretched to cover a much larger area when the avatar walks. I doubt there is a way around that for pencil and simple A-line skirts. 

With full circle skirts and creative use of the UVMap and weighting one might be able to hide more of the distortion.

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I would just say to be patient, and keep working the weights. Weight painting is an art, just like any other part of the creation process. When you copy weights from the avastar defaults, they are very sharp and have very little blending between bones. Plus, those weights are guaranteed to be off. I'd blend between bones more, to make the transition more smooth. From your photo, it's pretty obvious to me where you need to do some work. You have very little light blue areas between the bones. I would not call myself a weigting pro, but I have weighted quite a few avatars and clothing items over my 3D career. I've only played around with skirt weight, as I'm not really a clothing designer. I'm an animator, but that also means that I've had to deal with weights more than most people.

That stretching between the legs can be lessened just like you would mitigate the stretching around a joint. You add a few more verts. It's not going to completely get rid of the stretching, but it will lessen it, and give you more control over the stretching. I personally would never put a pattern in that area, as this is where you are going to see the stretching the most.

Weighting is a long process of trial and error. If you aren't spending a couple hours on it, even for a skirt, then don't expect great results. Of course, the time also depends on how much experience you have. If you are new to weighting, expect to spend a full day or 2. The great part about weighting in Blender tho, is that once you have a set of PERFECT weights, you can use that skirt to transfer those weights to any other skirt you might make. So, it is worth it to spend as much time as needed.

Recently, I was helping some1 with their weighting and they asked if I would weight the dress for them, and they just pay me. If there is a decent market for this, I may start accepting more clients, but I'd like to see how this goes, tho with every1 using Blender and Avastar, it will be pretty easy to just trade blend files with all the correct weights. Then the creator can use those same weights for any similar skirt they make. Or send it to me to do any corrections really quickly.

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Sharie Criss wrote:

Are there more controlled ways of editing the mesh weights than weight painting?

There is a less controlled, more automatic way of creating mesh weights which produces very good results for skirts. It has been in Blender since version 2.4x. See http://www.sluniverse.com/php/vb/general-sl-discussion/49086-mesh-nda-lifted-15.html#post1026510

If you have to adjust the weights manually for some reason, there are weight gradient and blending tools available to smoothly interpolate bone influences across a mesh. They are documented here: http://wiki.blender.org/index.php/Doc:2.6/Manual/Modeling/Meshes/Vertex_Groups/Weight_Paint_Tools

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