Rain Shader Part 3 - Ripples

To complete all the neccessary Material Functions for the rain, I made some fully procedural ripples, which I planned to use for the puddles on the street. Since this one is very similar to the Drop Material Function I have described in Part 1, I will only go into changes, not the entire setup. I potentially could have combined those two functions, but decided that being able to control them independently was something I definitely wanted.

Exactly as with the drops I set up the UVs and use a SphereMask to draw the drops. However this time I change the radius over time, again using the hash function to generate a random offset. I also got rid of the Distortion and position offset, since I wanted to utilize the entire UV square for the ripples instead of only a part, like with the drops.

Base Setup

Having this setup, I could move on to actually making the ripples. To get the rings for the ripples I feed the result of the spheremask into a sine node and make them fade out over time.



To get multiple ripples I multiply the sine node input by a number, the higher it is, the higher the number of ripples. I again use the random value to vary this number slightly.


To make the ripple fade, whilst moving away from the center, I use the UVs to create a mask, which looks like this.

Mask

For the ripples I only really need some good normals. Initially I was a bit worried about getting normals for a ring, but then I remembered, that the sine function returns a value range from -1 to 1. When using linear interpolate with an input A = 0, B = x and Alpha = -1 you receive -B as the result. For normals, when lerping between (0, 0, 1) and some Normals (x, y, 1) with Alpha = -1, the result is (-x, -y, 1).
To make things a bit clearer here is the formula for Linear Interpolate:

L = A * (1 - Alpha) + B * Alpha

That way I get these normals. I want to point out though, that they don't align with the mask anymore. You'd have to do some further maths to fix that, but since I don't need the mask I skipped that step.


This concludes the Rain Material Functions. I will still have to include them in the Master Materials. They where a fun learning experience in the realm of procedural shaders. Here is the complete Function setup plus a close up of the new parts.

MF_Rain_Ripples

NOTE: These ended up not being visible in our level, since we decided to have relatively shallow puddles.