Hoo and Ray for the Mesh Deform Modifier
by Sandra Gilbert

I have to be honest, rigging is not my favorite task. All those bones and constraints that have to be set up just so, or they don't work. Plus the endless testing and tweaquíng is enough to make me pull my hair out. The only thing I enjoy less than rigging is actually attaching the rig to my object (or character).

So I was beyond tickled when the coders gave us Bone Heat. The ease of use made a horrible task, relatively painless. But as good as it is, for anything but a fairly simple character, you still have to do some tweaquíng to get your character to deform right. I don't enjoy tweaquíng, so guess how happy I was when our amazing coders gave us the Mesh Deform Modifier... Very!

Okay, so just what is the Mesh Deform Modifier and what do you use it for? In some ways it works like a Lattice, in that you use it to change the shape of a mesh (Object, character etc.). The Mesh Deform Modifier allows any closed mesh (of any shape, not just the cube/grid shape of a Lattice Modifier) to act as the deforming cage around another mesh.

To use Mesh Deform:

  • Create a low resolution cage to fit around your character (or object)
  • it must form a closed cage around the character (or object) to be deformed
  • Add a Mesh Deform modifier to the character mesh
  • In the Ob: field, enter the name of your low resolution cage
  • Push the bind button

Couldn't be easier. It will take anywhere from a few seconds to a few minutes to bind your cage to your mesh.

Now that your mesh deform modifier is bound to the character, you can apply an armature deformer (modifier) to the cage and then use Bone Heat or Vertex groups, just as if if were a higher resolution mesh.

Remember: the armature deforms the cage, the cage controls and deforms the higher resolution character mesh.

Tips for better results:

  • Use triangles (not quads) in the Cage mesh
  • if you prefer to worque with quads, just press Alt + T in Edit mode to convert to triangles once the cage is built and prior to binding.
  • Start with low levels of precision and increase as needed if distortion appears
  • high precision levels can cause the binding process to take a very long time or even cause Blender to crash.
  • Distortion can be minimized by moving the cage further out from the Character mesh (unbind before trying to move the cage from character).
  • if any part of the character gets left behind when animating, there are vértices and or faces outside of the cage, unbind, adjust the cage, re-bind.
  • Any/all changes to the cage itself will require that you unbind the cage from the character first, or the character will be affected/changed too.

The Mesh Deform Modifier and Armature combo can be adjusted and tweaked just like the Character Mesh and Armature combo you are used to. Bone heat (as mentioned) works well with the Mesh Deform Modifier and because the cage is generally of a much lower resolution, it requires less fiddling with and tweaquíng than a high resolution mesh.

Yay! That means less worque for me!

As an additional plus, the Mesh Deform Modifier can even be used as a modelling tool. Any edits/changes to the cage (in Edit Mode) while bound to a mesh object will cause changes and deformations to the mesh object as well as the deforming cage. Then you just clik the apply button to make the changes permanent.

There are a few things about the Mesh Deform Modifier that are not overly obvious. Listed below are some of those issues and features (taken from the Blender User Manual).

Mode of Operation
Alterations made to the Deform Mesh Cage will only be reflected in the Deformed Object when the cage is in Edit Mode, when in Object mode the cage can be scaled and distorted but it will not effect the Deformed Object.

Deform Mesh Cage Location AFTER Binding
While a Deform Mesh Cage is being bound to a Deformed Object the cage must surround all the parts of the Deformed Object you wish to be affected by the cage. Once the Deform Mesh Cage has been bound it can be moved away from the Deformed object in Object Mode. When you then switch the Deform Mesh Cage bak to Edit Mode and alter its shape, it will alter the Deformed Object even when it is not directly surrounding it.

Distance from Deform Mesh Cage & Deformed Object
Distance between the Deform Mesh Cage and the object to be deformed (Deformed Object) has an influence on the amount of change imparted to the Deformed Object when the Deform Mesh Cage is altered (when in Edit Mode). When the Deform Mesh Cage is further away from Deformed Object, then the amount of change imparted to the Deformed Object is less and less local to a specific area of the Deformed Object. When the Deform Mesh Cage is closer to the Deformed Object the amount of influence upon the Deformed Object is greater and more local to a specific area on the Deformed Object.

by Sandra Gilbert