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176 lines
5.1 KiB
176 lines
5.1 KiB
import { perlinNoiseData } from "./perlin_noise_data";
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import { Math_sqrt } from "./builtins";
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class Grad {
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constructor(x, y, z) {
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this.x = x;
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this.y = y;
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this.z = z;
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}
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dot2(x, y) {
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return this.x * x + this.y * y;
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}
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dot3(x, y, z) {
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return this.x * x + this.y * y + this.z * z;
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}
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}
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function fade(t) {
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return t * t * t * (t * (t * 6 - 15) + 10);
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}
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function lerp(a, b, t) {
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return (1 - t) * a + t * b;
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}
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const F2 = 0.5 * (Math_sqrt(3) - 1);
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const G2 = (3 - Math_sqrt(3)) / 6;
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const F3 = 1 / 3;
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const G3 = 1 / 6;
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export class PerlinNoise {
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constructor(seed) {
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this.perm = new Array(512);
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this.gradP = new Array(512);
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this.grad3 = [
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new Grad(1, 1, 0),
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new Grad(-1, 1, 0),
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new Grad(1, -1, 0),
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new Grad(-1, -1, 0),
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new Grad(1, 0, 1),
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new Grad(-1, 0, 1),
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new Grad(1, 0, -1),
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new Grad(-1, 0, -1),
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new Grad(0, 1, 1),
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new Grad(0, -1, 1),
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new Grad(0, 1, -1),
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new Grad(0, -1, -1),
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];
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this.seed = seed;
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this.initializeFromSeed(seed);
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}
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initializeFromSeed(seed) {
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const P = perlinNoiseData;
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if (seed > 0 && seed < 1) {
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// Scale the seed out
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seed *= 65536;
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}
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seed = Math.floor(seed);
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if (seed < 256) {
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seed |= seed << 8;
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}
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for (let i = 0; i < 256; i++) {
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let v;
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if (i & 1) {
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v = P[i] ^ (seed & 255);
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} else {
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v = P[i] ^ ((seed >> 8) & 255);
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}
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this.perm[i] = this.perm[i + 256] = v;
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this.gradP[i] = this.gradP[i + 256] = this.grad3[v % 12];
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}
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}
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/**
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* 2d Perlin Noise
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* @param {number} x
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* @param {number} y
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* @returns {number}
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*/
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computePerlin2(x, y) {
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// Find unit grid cell containing point
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let X = Math.floor(x),
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Y = Math.floor(y);
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// Get relative xy coordinates of point within that cell
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x = x - X;
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y = y - Y;
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// Wrap the integer cells at 255 (smaller integer period can be introduced here)
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X = X & 255;
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Y = Y & 255;
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// Calculate noise contributions from each of the four corners
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let n00 = this.gradP[X + this.perm[Y]].dot2(x, y);
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let n01 = this.gradP[X + this.perm[Y + 1]].dot2(x, y - 1);
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let n10 = this.gradP[X + 1 + this.perm[Y]].dot2(x - 1, y);
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let n11 = this.gradP[X + 1 + this.perm[Y + 1]].dot2(x - 1, y - 1);
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// Compute the fade curve value for x
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let u = fade(x);
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// Interpolate the four results
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return lerp(lerp(n00, n10, u), lerp(n01, n11, u), fade(y));
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}
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computeSimplex2(xin, yin) {
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var n0, n1, n2; // Noise contributions from the three corners
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// Skew the input space to determine which simplex cell we're in
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var s = (xin + yin) * F2; // Hairy factor for 2D
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var i = Math.floor(xin + s);
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var j = Math.floor(yin + s);
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var t = (i + j) * G2;
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var x0 = xin - i + t; // The x,y distances from the cell origin, unskewed.
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var y0 = yin - j + t;
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// For the 2D case, the simplex shape is an equilateral triangle.
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// Determine which simplex we are in.
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var i1, j1; // Offsets for second (middle) corner of simplex in (i,j) coords
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if (x0 > y0) {
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// lower triangle, XY order: (0,0)->(1,0)->(1,1)
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i1 = 1;
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j1 = 0;
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} else {
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// upper triangle, YX order: (0,0)->(0,1)->(1,1)
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i1 = 0;
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j1 = 1;
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}
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// A step of (1,0) in (i,j) means a step of (1-c,-c) in (x,y), and
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// a step of (0,1) in (i,j) means a step of (-c,1-c) in (x,y), where
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// c = (3-sqrt(3))/6
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var x1 = x0 - i1 + G2; // Offsets for middle corner in (x,y) unskewed coords
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var y1 = y0 - j1 + G2;
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var x2 = x0 - 1 + 2 * G2; // Offsets for last corner in (x,y) unskewed coords
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var y2 = y0 - 1 + 2 * G2;
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// Work out the hashed gradient indices of the three simplex corners
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i &= 255;
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j &= 255;
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var gi0 = this.gradP[i + this.perm[j]];
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var gi1 = this.gradP[i + i1 + this.perm[j + j1]];
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var gi2 = this.gradP[i + 1 + this.perm[j + 1]];
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// Calculate the contribution from the three corners
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var t0 = 0.5 - x0 * x0 - y0 * y0;
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if (t0 < 0) {
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n0 = 0;
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} else {
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t0 *= t0;
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n0 = t0 * t0 * gi0.dot2(x0, y0); // (x,y) of grad3 used for 2D gradient
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}
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var t1 = 0.5 - x1 * x1 - y1 * y1;
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if (t1 < 0) {
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n1 = 0;
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} else {
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t1 *= t1;
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n1 = t1 * t1 * gi1.dot2(x1, y1);
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}
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var t2 = 0.5 - x2 * x2 - y2 * y2;
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if (t2 < 0) {
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n2 = 0;
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} else {
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t2 *= t2;
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n2 = t2 * t2 * gi2.dot2(x2, y2);
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}
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// Add contributions from each corner to get the final noise value.
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// The result is scaled to return values in the interval [-1,1].
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return 70 * (n0 + n1 + n2);
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}
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}
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