GoKawiilFast and Gorgeous Erosion Filter
This blog post and the companion video both explain an erosion technique I’ve worked on over the past eight months. The video has lots of elaborate animated visuals, and is more focused on my process of discovering, refining, and evolving the technique, while this post has a bit more implementation details on the final iteration. I suggest watching the video first, but it’s not required. You can also skip right to the links at the end.
In the real world, rainfall on mountains tends to converge into water streams and rivers, which carve gullies in the mountain sides. These gullies may form branching patterns, as smaller water streams merge into larger ones. And the gullies often butt up against each other, leaving sharp ridges dividing them.
But when generating virtual landscapes, the simulation of countless water drops is slow. It’s not very suitable for generation in chunks either, which means it’s not practical to use when generating landscapes that are too large to generate all at once.
This means techniques are sought after, which can produce the appearance of erosion without having to deal with simulating the process of it. This post is about such a technique.
Screenshot of Advanced Terrain Erosion Filter Shadertoy by me.
It’s essentially a special kind of noise which produces gorgeous branching gullies and ridges, while still allowing every point to be evaluated in isolation, which means it’s fast, GPU-friendly, and trivial to generate in chunks.
Furthermore, rather than defining the landscape entirely, it can be applied on top of any height function, essentially applying erosion on top as a filter.
Background
There’s a website called Shadertoy where people create and share standalone shaders. A shader is a program that runs on the GPU, which can be used to determine what a virtual surface should look like, or for various other effects, or even entire scenes.
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