Fake(ish) wet footprints

I'm probably going to catch some flak for spending an entire day building wet footprints, but the way they looked in my last test render was kinda driving me nuts, so...

Long story short, the way I'm generating floor tiles is kinda weird (technically every tile is different and none of them repeat the same detail twice), which makes it exceptionally difficult to map a secondary texture onto them without killing render performance or having to deal with 16k or 32k texture maps. Furthermore, any texture based solutions would mean that the location and pattern of the footprints would be "set in stone" so to speak, and if those ever needed to be changed then all the textures driving those would also need to be redone.

So I needed a better way of creating wet footprints that was relatively clean and easy to apply to the scene, preferably without having to modify anything underneath the actual footprints.

This is the result of a slightly unorthodox system I came up with for handling exactly that.

The top half of this image is the Substance Designer graph that reads in a rough vector representation of a "clean" human footprint, distorts the hell out of it, then applies some image processing voodoo in order to generate a normal map that simulates the surface tension of water while sitting on a rough surface (in this case, black slate). The graph is designed so that the results can be randomized as many times as I need to generate unique results that all share the same rough features (this is important since no two wet footprints should ever be the same).

The second part of this workaround involves a set of 2D planes hovering just above the surface of the tiles. The planes are procedurally generated within the scene and follow a guide spline, so that the path and location of the footprints can be altered in seconds without having to change anything else.

The shaders for the "wet footprints" (and associated water droplets) were then configured to create the illusion of two different things: 

1) A darkening effect of both the tile surface and grout color, simulating the appearance of a wet surface

2) Clamping of the secondary diffuse/specular ray bounces, simulating the IOR shift in reflectivity that occurs when a surface is in direct contact with water (IOR = 1.333) rather than air (IOR = 1.0)

This is probably a hilariously minor detail in the grand scheme of things that likely didn't deserve as much time and effort as I threw at it, but I wanted to see if I could create a more convincing effect that didn't look like perfectly shaped footprints stamped out across the surface of the tiles.