Method noise

Source/Utils/SimplexIslands.hpp:76–127

2D simplex noise

	// 2D simplex noise
	double noise(double xin, double yin) {
		double n0, n1, n2; // Noise contributions from the three corners
		// Skew the input space to determine which simplex cell we're in
		double s = (xin + yin)*F2; // Hairy factor for 2D
		int i = fastfloor(xin + s);
		int j = fastfloor(yin + s);
		double t = (i + j)*G2;
		double X0 = i - t; // Unskew the cell origin back to (x,y) space
		double Y0 = j - t;
		double x0 = xin - X0; // The x,y distances from the cell origin
		double y0 = yin - Y0;
		// For the 2D case, the simplex shape is an equilateral triangle.
		// Determine which simplex we are in.
		int i1, j1; // Offsets for second (middle) corner of simplex in (i,j) coords
		if (x0 > y0) { i1 = 1; j1 = 0; } // lower triangle, XY order: (0,0)->(1,0)->(1,1)
		else { i1 = 0; j1 = 1; }      // upper triangle, YX order: (0,0)->(0,1)->(1,1)
		// A step of (1,0) in (i,j) means a step of (1-c,-c) in (x,y), and
		// a step of (0,1) in (i,j) means a step of (-c,1-c) in (x,y), where
		// c = (3-sqrt(3))/6
		double x1 = x0 - i1 + G2; // Offsets for middle corner in (x,y) unskewed coords
		double y1 = y0 - j1 + G2;
		double x2 = x0 - 1.0 + 2.0 * G2; // Offsets for last corner in (x,y) unskewed coords
		double y2 = y0 - 1.0 + 2.0 * G2;
		// Work out the hashed gradient indices of the three simplex corners
		int ii = i & 255;
		int jj = j & 255;
		int gi0 = permMod12[ii + perm[jj]];
		int gi1 = permMod12[ii + i1 + perm[jj + j1]];
		int gi2 = permMod12[ii + 1 + perm[jj + 1]];
		// Calculate the contribution from the three corners
		double t0 = 0.5 - x0 * x0 - y0 * y0;
		if (t0 < 0) n0 = 0.0;
		else {
			t0 *= t0;
			n0 = t0 * t0 * dot(grad3[gi0], x0, y0);  // (x,y) of grad3 used for 2D gradient
		}
		double t1 = 0.5 - x1 * x1 - y1 * y1;
		if (t1 < 0) n1 = 0.0;
		else {
			t1 *= t1;
			n1 = t1 * t1 * dot(grad3[gi1], x1, y1);
		}
		double t2 = 0.5 - x2 * x2 - y2 * y2;
		if (t2 < 0) n2 = 0.0;
		else {
			t2 *= t2;
			n2 = t2 * t2 * dot(grad3[gi2], x2, y2);
		}
		// Add contributions from each corner to get the final noise value.
		// The result is scaled to return values in the interval [-1,1].
		return 70.0 * (n0 + n1 + n2);
	}

	std::vector<std::vector<float>> generateOctavedSimplexNoise(int width, int height, int octaves, float roughness, float scale, short seed) {
		std::vector<std::vector<float>> totalNoise;