Per-pixel blend between two unrelated dynamic materials

In my current project, every object can be manipulated by the user, allowing them to switch between arbitrary combinations of meshes and materials.

When one of these changes occurs, I want to make the switch less jarring by playing a ‘flash’ animation, as seen in this image:

42473-switch.gif

I’m currently doing this by having a ScalarParameter on my master material’s Emissive channel. The impact of this is that every single material in the game must be an instance of the master material, or have a matching parameter.

What I’d really like to do instead is to make my ‘flash’ its own material, then simply interpolate a blend with whatever material the selected object has. The advantage of this is that I don’t have to do any special setup with each and every material I use.

I’m targeting mobile devices as well, so I can’t really use any post-processing features.