Perlin noise | Hacker News Reader

Perlin noise

eev.ee

113 pointsbpierre18 comments

When I was in high school I used Perlin noise to create some 3D terrain. Being young and naive I emailed Ken Perlin and asked him some questions about it. To my surprise he responded and was super nice :-)

As a student at NYU working with him on one of his research projects, I can confirm that yes, he's a pretty nice guy.

See also Simplex Noise, Perlin's 2001 replacement --- it extends to an arbitrary number of dimensions, and it's cheaper:

http://webstaff.itn.liu.se/~stegu/simplexnoise/simplexnoise....

Time to post his website again http://mrl.nyu.edu/~perlin/

Needs to be ported to webgl some day

> Needs to be ported to webgl some day

There are many shader implementations of continuous noise. Most should be WebGL compatible.

EDIT: https://github.com/ashima/webgl-noise there you go :) Includes classic noise (Perlin I guess?) and Simplex.

There's another cool WebGL simplex demo here: http://alteredqualia.com/three/examples/webgl_terrain_dynami...

I posted it because he has dozens of demos like the noise generation, all written in Java unfortunately.

This is a really nice write up! The graphs really show how a noise signal is built up of its components. Additionally, while un intentional, it also shows how Perlin noise can exhibit "gridding" artifacts from the regular spacing at integer boundaries. This is especially true when used to create tangents based on the signal.

Yep; as described in the "Improving Noise" article, the gridding is greatly reduced if you use the "smootherstep" function which has a continuous second derivative in addition to first.

Fun fact: there is a C reference implementation of Perlin noise directly in the svg specification : https://www.w3.org/TR/SVG/filters.html#feTurbulenceElement

Ah, the classic!

There's tons of other lovely noises too. Interested in more? Check out some SIGGRAPH stuffs from Mr. Perlin.

I found the following libnoise (C++ Perlin noise lib) tutorial very helpful:

http://libnoise.sourceforge.net/tutorials/index.html

Hmm... Perlin noise is a lot more complex to generate than I was expecting.

You don't win an Academy Award for Technical Achievement for Math.random()!

Many folks looking for a Perlin-like effect end up using the diamond-square(or "midpoint displacement") algorithm, which has a similar look but a somewhat simpler implementation:

For each segment take the midpoint of the linear interpolation and add noise at a smaller magnitude. Recurse in until you are at the desired scale. In 2D, flip the sample points between a "square" pattern and a "diamond" pattern each time to avoid a boxy tiled look.

The biggest downside of this method is that it's much less flexible about scaling: to get more resolution you have to double each dimension.

I remember implementing simplex noise in verilog a few years ago. It took me a while to get my head around it, but eventually something just clicked, and the results were very impressive too.

Can't this be done more easily by solving a differential equation and setting some random boundary conditions?

No not at all. Think for a bit about what the closed form solution of the final generated function is for any of the examples given. Then think of the differential equation that it satisfies (with N boundary conditions for every segment of the partition). There's no way solving that is easier than what is done in the article. Even before doing that, there are plenty of other methods that still aren't as efficient, which was one of the main goals of the algorithm.

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