Version: 2.77 (linux 64bit)
How to reproduce:
- Open attached file and inspect the grid object's modifers, weights and shape keys
- Note how the vertex weight modifier has no effect on the resulting shape, when it should
- Note how no feature that dynamically affects the vertex weight (dynamic paint or vertex weight modifiers) has an effect on the resulting mesh shape key
Procedural changes to a vertex group should affect the shape keys influenced by that group. Not being able to dynamically effect the vertex weight of a shape key is a pretty serious limitation. One can imagine a lot of uses which are currently closed to the user.