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I've been lurking on the forum for a long time. I'm not exactly new to blender, but I haven't started so long ago. And I happened to run into a problem that I couldn't find the solution for on the internet or by myself.

When setting up my rig for my humanoïd character (semi-realistic woman), I notice than when I bend her back, her stomach deforms in a weird way and becomes smaller when it should be sticking out a little bit. I've tried to craete more bones with stretch to constraints but it results in just making "ripples" on the stomach and looks even worse.

Here are the screenshots:

Side View

Problems Occuring

I think that my topology, although not perfect, is pretty good. And i've had the same problem and all of my other humanoïd models.

Do you have an example of a rig I could set up or of a deformer I could apply or is it normal?

Thank you in advance.

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  • $\begingroup$ Hi, for some reason, your screenshots are not in the post... $\endgroup$ – m.ardito Jul 13 '17 at 11:31
  • $\begingroup$ I can't help you more on this, since your model/rig is quite complex, but are you using the "preserve volume" in the armature modfier? could it help somehow? $\endgroup$ – m.ardito Jul 13 '17 at 11:53
  • $\begingroup$ I do forget to turn it on from time to time, but yes I am using it and the problem happens regardless. :/ $\endgroup$ – Dalieday Jul 13 '17 at 11:55
  • $\begingroup$ Not much into rigging myself so take this with a grain of salt, but this may very well be the limits of what a rigging system can achieve alone in Blender. It doesn't really take into account self collisions nor mass or volume like in the real world, and is not physics based. If you want a stomach to protrude while bending you may have to do that manually with shapekeys or other manual adjustments. $\endgroup$ – Duarte Farrajota Ramos Jul 13 '17 at 19:33
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I've managed to improve, but not solve, the deformation problem that I had by doing the following:

1: I slightly changed the mesh, making the stomach portrude more and making a nicer back bend. That enables me to bend the back less to achieve the illusion of a bend.

2: I divided the lower spine in 3 bones instead of 4 and shifted the whole spine and chest more to the centre of the mesh.

I think it looks significantly better and the side bends (wich I will not show) look pleasant.

Changes

Deformation

I will still work on it and try to add strech bones. Maybe it will help. Or maybe, as someone has suggested, this is the limit of the blender rigging system and I will have to rely on shape keys.

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