how to make perlin noise

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Technical Problem Cluster First Answered On January 19, 2022 Popularity 9/10 Helpfulness 2/10

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perlin noise generator

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perlin noise generator

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class Vector2 {
	constructor(x, y){
		this.x = x;
		this.y = y;
	}
	dot(other){
		return this.x*other.x + this.y*other.y;
	}
}

function Shuffle(tab){
	for(let e = tab.length-1; e > 0; e--){
		let index = Math.round(Math.random()*(e-1)),
			temp  = tab[e];
		
		tab[e] = tab[index];
		tab[index] = temp;
	}
}

function MakePermutation(){
	let P = [];
	for(let i = 0; i < 256; i++){
		P.push(i);
	}
	Shuffle(P);
	for(let i = 0; i < 256; i++){
		P.push(P[i]);
	}
	
	return P;
}
let P = MakePermutation();

function GetConstantVector(v){
	//v is the value from the permutation table
	let h = v & 3;
	if(h == 0)
		return new Vector2(1.0, 1.0);
	else if(h == 1)
		return new Vector2(-1.0, 1.0);
	else if(h == 2)
		return new Vector2(-1.0, -1.0);
	else
		return new Vector2(1.0, -1.0);
}

function Fade(t){
	return ((6*t - 15)*t + 10)*t*t*t;
}

function Lerp(t, a1, a2){
	return a1 + t*(a2-a1);
}

function Noise2D(x, y){
	let X = Math.floor(x) & 255;
	let Y = Math.floor(y) & 255;

	let xf = x-Math.floor(x);
	let yf = y-Math.floor(y);

	let topRight = new Vector2(xf-1.0, yf-1.0);
	let topLeft = new Vector2(xf, yf-1.0);
	let bottomRight = new Vector2(xf-1.0, yf);
	let bottomLeft = new Vector2(xf, yf);
	
	//Select a value in the array for each of the 4 corners
	let valueTopRight = P[P[X+1]+Y+1];
	let valueTopLeft = P[P[X]+Y+1];
	let valueBottomRight = P[P[X+1]+Y];
	let valueBottomLeft = P[P[X]+Y];
	
	let dotTopRight = topRight.dot(GetConstantVector(valueTopRight));
	let dotTopLeft = topLeft.dot(GetConstantVector(valueTopLeft));
	let dotBottomRight = bottomRight.dot(GetConstantVector(valueBottomRight));
	let dotBottomLeft = bottomLeft.dot(GetConstantVector(valueBottomLeft));
	
	let u = Fade(xf);
	let v = Fade(yf);
	
	return Lerp(u,
		Lerp(v, dotBottomLeft, dotTopLeft),
		Lerp(v, dotBottomRight, dotTopRight)
	);

}

Popularity 9/10 Helpfulness 2/10 Language whatever

Source: rtouti.github.io

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Contributed on Jan 19 2022

Strange Stoat

2 Answers Avg Quality 1/10

how to make perlin noise

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