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A port of Evan Wallace's "Water Demo" for WebGL to Unity.

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Water Demo

Water demo GIF showing caustics.

This is a port of Evan Wallace's Water Demo from WebGL to Unity.


I ported this as an exercise to investigate different real-time caustics implementations. I've only surveyed a handful of research papers on real-time caustics, but it seems like Evan's work would be suitable for publication for both its simplicity and performance.


  • Unity 2018.2.17f1


Create a new project using Unity 2018.2.17f1. Clone this repo into the "Assets" directory. Open the "cube-of-water" scene and hit play.

Click on water to cause a wave.

You can click on the water to cause a wave. You can drag to move the camera around. Hit "space" key to pause water simulation. Hit "n" key to update the simulation one time step.

Implementation Notes

This is a pretty faithful reproduction of Evan's demo. As such there are a number of cases where it deviates from Unity's conventions.

For instance, the shader that renders the sphere has variable

, so the sphere rendering object is expected to located at the origin and if you change that, it probably will not look right.

The light direction is provided to shaders as a direction vector. It doesn't use Unity's lighting at all.

The shaders do not use the models' UV coordinates. For instance the cube's minimum and maximum model position are (-1, -1, -1) and (1, 1, 1), so any point on its surface is often just mapped directly to a UV coordinate [0, 1]^2 by transforming the point p by

p * 0.5 + 0.5
. This works fine for the purposes of the demo, but one would probably want to switch to UV coordinates in the future.

A lot of this is smoke and mirrors. The cube knows where the sphere is, so it renders its shadow. Great for a tech demo, but if you want to allow for multiple spheres or other objects, this will need to be reformulated significantly.


  • WebGL build not working (major regression from original project).

  • Not all UI elements from original are preserved.

  • Underside of water does not reflect like it should. Seems like a HLSL lerp problem.

See the
file for more details.


This project is released under the MIT license.

The tiles texture appears to be Patrick Hoesly's and was released under the Creative Commons Attribution (CC-BY) license.


I won't be providing any support for this, but if you want to follow me and the strange things I make you can find me on twitter @shanecelis.

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