Every vertex in a 3D mesh has an associated number. The order of the vertices is based on this number. When moving a 3D mesh from one software to another or even editing within the same software, vertex order can be altered. Imagine we have a cube with 8 vertices numbered 0, 1, 2, 3, 4, 5, 6, and 7. The top plane could consist of vertices 0, 2, 4, and 5. We could have another cube where the top plane consists of 0, 1, 2, and 3. Even though the number of vertices is the same and the shape is identical, from the computer’s standpoint, these are different meshes because the vertex order is different.
If one mesh represents a morph of the other, then we sill see an exploding mesh because the vertex order is different. This is easy to fix for a cube by manual reconstruction but imagine this happens on a mesh consisting of more than hundreds of thousands of vertices?
There is a tool in Maya that will help. Below are two videos showing Maya’s vertex reordering feature in action.
Another tool that can help is R3DS Wrap. From their website, “Wrap makes it possible to take an existing basemesh and non-rigidly fit it to each and every scan.” With this tool, you could take your original mesh and wrap it to another mesh with bad vertex order.