For reference, this information might be too specific, but I couldn't find a better place for it, so I'm posting it here.
The appearance of a "grayed-out" stack depends on the coordinates
Whether a "grayed-out" stack appears or not depends on the following condition:
([ax + by + cz + d] mod 32768) mod 100 < 50, where
a = 2992.911117
b = 14174.264968
c = 5325.181015
d = 32788.727920
0 <= x <= 143
0 <= y <= 143
z = 0 for the surface
z = 1 for the underground
[x] = floor(x)
A "grayed-out" stack will appear if the condition is met.
Location of neutral creatures with a "grayed-out" stack for a 144 x 144 map with an underground and without
0 - no "grayed-out" stack, 1 - "grayed-out" stack exists.
You can check a cell (x, y, z) for a "grayed-out" stack using the Bitmap Generator program.
I integrated a "grayed-out" stack viewer into the WT addon, but unfortunately, the formula is incorrect.
That's what I initially thought....
But now I've decided to add more information: if your troops are strong enough and the neutral creatures merge into a single stack, there will be no "grayed-out" stack.