Need help with automatic weighting problem

In the attached blend file there is a yet-to-be-parented mesh and an armature consisting of two bones. When the mesh is parented to the armature using automatic weighting the bone weights are improperly distributed and the deformation is warped when posing with the top bone. This has happened once while trying to rig a fully-modelled character and it was a huge setback. Please can anyone find the solution to this? Thanks.


Problem–Improper_Bone_Automatic_Weighting.blend (460 KB)

that is unexpected! One thing that helped a little was I dissolved every other horizontal loop and thus simplified the mesh. I reparented it and it was still a little weird but the weights were better.

perhaps you just had an unnecessarily complex mesh

Unapplied and negative object scale. You are looking at an inverted and scaled version of what tools and modifiers see.

Ctrl+A -> scale to apply. Because the scale was negative, it flips the mesh normals. Edit mode, select all, ctrl+N to make normals consistent and pointing out.

Also apply the object scale for the armature object.

Take a look at this from the manual.

This is a common thing. You need to manually adjust the weights.

The bone heat on automatic weights looks to see what influence each vertex has to the bone based upon distance. If that is not what you want (like in your case), you need to manually adjust the weights. If you use the automatic weights you almost always need to adjust them.

Here is a good primer on that and if you have questions, you can post back.

If you have time take a look at the whole series. It is really done well. If you have trouble with weight painting, I’d also recommend a trip over to cgcookie. That will save you a lot of heartache.

After you adjust the mesh as recommended.

Thanks guys! I tried the suggestions and I found out that the problem was as JA12 pointed – Unapplied and negative object scale. Not only have I used it to fix this problem but I’ve also applied it on the problematic character model I abandoned years ago due to this very problem and it worked perfectly! Thanks!!!