Todor Nikolov writes:
The Voxel Heat Diffuse Skinning addon is a bone-weighting algorithm similar to Blender's "Automatic Weights". However, it solves many of the problems with the default feature.
For one thing, it never fails with "Bone heat weighting error...".
It is also great when weighting overlapping geometry such as body and clothing.
Of course, this add-on is not ideal for every situation. There are cases when you still may want to use Automatic Weights instead of Voxel Heat.
In this video tutorial, I show the strengths and weaknesses of Voxel Heat Diffuse Skinning, and how and when to use it. And when to rely on other techniques.