noise() is not Perlin noise

noise() is not Perlin noise

Hi,

I've been browsing the documentation of the noise function

[...] Ken Perlin invented noise() while animating the original Tron film in the 1980s

and continued to study its implementation. From a first sight, I believe that the implementation found in p5.js deviates from Perlin noise in two characteristics:

Perlin noise defines gradients at integer grid locations

The noise value associated with a grid locations is given by the dot-product between the stored gradient and the offset vector. If I read your implementation correctly, you are directly assigning a random value to each integer location that is later interpolated.

Perlin noise is zero at all integer grid locations

if the dot-product becomes zero, either because of orthogonality between the gradient direction and the offset vector or because the offset vector is zero (at integer locations), the resulting noise value becomes zero. Hence, at integer locations the resulting noise should be zero. See https://en.wikipedia.org/wiki/Perlin_noise. In p5.js noise(x=0,0,0) will not return a zero noise value in general.

Hence, noise() provides smooth noise, but not Perlin noise. I don't believe that's an issue for the intended audience, but in case one relies on the above Perlin characteristics to hold true, you should mentioned the deviations in the docs.

Start by reading the noise() documentation and the p5.js noise() implementation referenced in the issue. Compare the documented Perlin-noise claims with the implementation's grid values and integer-coordinate behavior, then update the documentation so its description accurately states any deviations.