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  • Writer's pictureJayden Zhang

Procedurally Generated Water Shader in UE4

Updated: Dec 17, 2019

Based on Research From

GPU Gems, Chapter 1. Effective Water Simulation from Physical Models, NVIDIA: https://developer.nvidia.com/gpugems/GPUGems/gpugems_ch01.html


Github Link


Result


Brief Introduction

This project is mainly trying to research and implement water shader based on GPU Gems Chapter 1 , the goal for the project is to create a believable, variant water shader that can provide dynamic visual looks, with large seamless scale water volume yet still have decent performance that can run on a modern GPU at realtime.

Materials and Material Functions Structure


Core Material

----MODULE BREAKDOWN----

Basic Mathematics / Algorithms / Terms

The biggest challenge is to implement the shader in Unreal, by manipulating the water surface vertex in real-time.

According to the book, the key to simulate realistic water waves is to blend multiple sine waves together, then manipulate them to give them a more natural look. (Gerstner Wave function for example)

Base Color

Firstly, base color is simply just a tint of distorted scene color (which creates a refraction effect, see "Refraction" below), then it is interpolated by a depth test, to mimic the feeling of depth.


Mathematically Generated Height

Since the wave function is using gerstner:

This function can be translated to unreal hlsl by:

Where float3 WavePos; float CigmaX; float CigmaY and float CigmaZ are all inputs from outside





Procedurally Generated Normal

The normal will be:


Which is the cross product of a vertex's Binormal and Tangent, in Unreal hlsl:

Here, DDX H(X,Y,T) is used to calculate the mix of all four curves:

Distance-Based Tessellation

Refraction

Refraction is using a distort of the sample uv of background scene color buffer:





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