Detail this asset from Unity Asset Store: https://assetstore.unity.com/packages/2d/textures-materials/advanced-road-material-33414
But now you can download Advanced Road Material FREE.
Advanced Road Material v1.0
This is a dynamic road material that can create almost unlimited amount variations.
Use with the awesome EasyRoads3D or Easyroads3D Free
It has variables to add water for if its raining, snow, moss. The moss can be colored to simulate dirt.
Add variants of pot holes, cracks, damage and more.
Then, there are many options to add road markings, assign its colors. All this gives an almost unlimited amount of possibilities.
Can use diffuse, specular and parallax shaders.
If that wasn’t enough there’s even a script that makes it easy to change the snow, wetness, moss and ice levels at runtime from your code.
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