In this tutorial we will go through the process of creating realistic wet materials. Although the tutorial is written for max and vray users, the same workflow can be adapted to any software you may use.

1) Analyzing the reference
In order to re-create any type of material the first and most important thing is to look at real photos of what you are trying to replicate in your rendering, and really understand what is happening there.

For example, take a close look at the photo bellow.

Not only the asphalt is quite reflective because of the layer of water on it, but also the glossiness/specular varies a lot across the image. In areas where the layer of water is thicker the reflections are a lot sharper and the bump of the asphalt is less present. In other areas, where the asphalt is dryer, the reflections become glossy and they are also distorted by the bumps on the street.

2) Replicating the effect with 3ds max tools and vray.
To sum it up, in order to create a wet asphalt shader we need a diffuse map, a bump map, a reflection map and most importantly a map for the glossiness chanel.
Open the “wet materials scene” that you find in this zip file.

Although all the maps are already there, they are not activated yet; we will activate them one by one to better understand how each of them affects the overall look.

a)    The reflection map

For the reflection, I have used a falloff with 2 maps (basically a darker version and a lighter version), for more control. Besides the brightness both maps are identical.
The areas close to the edges (where I want the layer of water to be thicker) are whiter and more uniform, while other areas are darker and noisy.

Activate the reflection map by clicking the checkbox next to it in the maps rollout.
If you hit render, at this stage you will end up with something like this:

b)    The bump map
If you activate the map and hit render you will notice that the reflections are distorted in the areas where the map has noise applied. Again, in other areas where there is more water, you need to paint it with neutral gray, since there is no bumpiness.

c)    The reflection glossiness map
This one makes all the difference. Before activating it, the reflection, although distorted by the bump map in some place is still very sharp an unnatural. As we have noticed from the reference image at the beginning of the tutorial, this should vary across the image, depending again by the thickness of the layer of water. White causes the reflection to be sharp (equivalent to “1” from the glossiness parameter), while darker values make the reflection much more glossy.
If you hit a render after having activated it, you will end up with something like the following:

d)    The diffuse map.
Although not really important for the purpose of this tutorial, it has quite an impact on the realism of the image, so activate that as well and hit a final render.

If there is something you don’t understand or if you have any kind of questions, don’t hesitate to ask.