Rain Shader
SCroll down for process and more
This environmental rain uses some clever shader work to let environment artists further along in the pipeline paint puddles onto a mesh in realtime. You can see below that after the material has been applied to your mesh or landscape, you can paint into the red channel of each vertex in the editor in real time. This is a high quality shader utilizing tesselation and vertex displacement, so it is a high poly setup. This would work fine in a small alley environment for instance, but in a larger context this would just need to be applied to the landscape materials with different blending layers. Same result just different method, this one being more expensive and a little bit prettier.
Please give this HD gif some time to load. :)
In the puddle shader, I used math and science to pan lines across the UV space and changed the UV coordinates to a seamless map of radial gradients. Tiling and overlaying this map in different ways gives off a seemingly random ripple texture.
When the puddles are overlaid, all the relevant changes are made in the roughness, normals, etc. But the fun part was adding a bump offset to the bricks so that they have the illusion that they are sunken beneath the puddle. The puddles will only accumulate where the ground is lower, after all.
Oh, and the white cube is there just to show off the reflections.