I am trying to animate a voxel (cubic) model I made in MagicaVoxel using Blender, but when I try to move the feet, the soles of the feet badly deform. Also, when I move the hands, it slightly deforms the shoulder a little bit. This is my first time using blender, so I figured I would need some help for this fix. I want to be able to move the feet, hands, and head without having them deform.
Tweaked three things and got it to work.
Tris to Quads
The first thing I did was Tab into Edit Mode and key Alt + J to convert Tris to Quads. This is a form of retopologizing that is highly recommended. Triangles are not recommended when modeling.
I keyed W to open the Specials menu and selected Remove Doubles. This got rid of excess duplicate vertices that were messing with your Weight Painting. Of course, this destroyed the shading, so I added an Edge Split modifier in the Properties panel > Object modifiers tab.
After all the changes to the mesh, I redid the parenting. I selected the mesh, then selected the armature, keyed Ctrl + P, and chose Armature Deform > With Automatic Weights.
Here is the fixed .blend file: