In my C4D days I wrote a shader to sit on top of others to simulate wetness. Finally decided to try the same again here. This is more advanced than the C4D one, and is driven by the Z position of the empty. The empty is restricted to movement only in the Z axis, between 0cm and 100cm, and so the Z value is effectively a percentage driver.
The standing water is a separate plane, and the maths that drives it doesn’t produce a linear effect. In particular, between 22% and 25% the difference is extremely noticable. Unfortunately, it can’t just use the same value as the wetness on the brick shader, since it gets overblown far too quickly.
Anything more than 50% is probably overdoing it, too. Both the plane standing water and the wetness are driven by the empty, and designed to work together.
A short video at https://youtu.be/Ril_QlhC15g
And the blend is attached The HDRI is available at https://polyhaven.com/a/furry_clouds. The brick textures are available at https://polyhaven.com/a/castle_brick_02_red (too big to upload when packed).
Note that the displacement is via a displacement modifier rather than a displacement node. The displacement node doesn’t react properly, and provides a too flat result.
.blend file if anyone wants to play with it is attached.
wetness.blend (140.8 KB)