bone heat weighting: failed to find solution for one or more bones error message

Question

Here it goes again, the rigging error. I have a model that has a mirror modifier already applied and a subsurface and displace modifier (not applied) in my model. So when I try to parent my model to my armature it gets the bone heat error message, but before I applied the mirror modifier it worked, although the bones only work on the left side and the right side didn't work at all.

Solutions I have tried:

• Remove doubles (doesn't work)
• Recalculate (doesn't work either)
• Remove all modifiers (no luck)
• Place the root bone at the center of the model (still get the error)
• Apply the subsurface modifier and parent them (no result)
• Apply the decimate planar modifier (this works, but the decimate modifier destroys my seam marked on my model, which causes my displace modifier to not function well because I baked my displace map with another model that has a multiresolution level of four).

blender file:

I have the unapplied mirror modifier model in layer 3 and applied mirror modifier model in layer 1.

Answer 1

Your trouble shooting is pretty good already. Other useful steps for the future are:

• Append the armature datablock and the mesh datablock into a new file. Then create new armature and mesh object and select (link) the appended datablocks. Try it with these clean objects again.
• Remove all vertices groups. (There was a group left called "group".)
• Remove the UV data.
• Remove the constraints on the armature.

None of these get us any further in your case.
I also tried to reproduce the problem in a controled environment and failed.

Since it works with the decimate modifier applied, we know it must be a topology error.

As batFINGER suggested you can find non manifold geometry with Select Non Manifold operation (Ctrl+AltShift+M). This will select the the non manifold geometry.

There is non manifold geometry in the tip of the tail.

Most of it doesn't cause any errors though except two vertices.

As you can see in the image, there are to vertices which are connected to overlapping faces. Delete the vertices and Parent > Armature Deform with automatic weights will work.

(Click to enlarge.)

Answer 2

From my experience, the following steps solved all my armature heat problems I had so far (considering one mesh, where all vertices and edges form exactly one connected graph):

1. Remove doubles
2. Recalculate normals
3. Remove all modifiers from the object
4. reset pose from the armature, if any
5. decimate mesh using planar
6. decimate mesh using un subdivision

The last 2 points are the best ways to overcome the problem. If none of it works, just increase degrees on the decimate up to point where armature deform will succeed. Then you can find optimal decimation to lose as less data as possible. However, if you sculpt it, later on, dealing with decimated topo from planar decimation is not such a big deal.