+#include "noise.hpp"
+
+#include <cmath>
+
+
+namespace blank {
+
+
+SimplexNoise::SimplexNoise(unsigned int seed)
+: grad({
+ { 1.0f, 1.0f, 0.0f },
+ { -1.0f, 1.0f, 0.0f },
+ { 1.0f, -1.0f, 0.0f },
+ { -1.0f, -1.0f, 0.0f },
+ { 1.0f, 0.0f, 1.0f },
+ { -1.0f, 0.0f, 1.0f },
+ { 1.0f, 0.0f, -1.0f },
+ { -1.0f, 0.0f, -1.0f },
+ { 0.0f, 1.0f, 1.0f },
+ { 0.0f, -1.0f, 1.0f },
+ { 0.0f, 1.0f, -1.0f },
+ { 0.0f, -1.0f, -1.0f },
+}) {
+ unsigned int val = seed;
+ for (size_t i = 0; i < 256; ++i) {
+ val = 2346765 * val + 6446345;
+ perm[i] = val % 256;
+ }
+}
+
+
+float SimplexNoise::operator ()(const glm::vec3 &in) const {
+ float skew = (in.x + in.y + in.z) / 3.0f;
+
+ glm::vec3 skewed(std::floor(in.x + skew), std::floor(in.y + skew), std::floor(in.z + skew));
+ float tr = (skewed.x + skewed.y + skewed.z) / 6.0f;
+
+ glm::vec3 unskewed(skewed.x - tr, skewed.y - tr, skewed.z - tr);
+ glm::vec3 offset[4];
+ offset[0] = in - unskewed;
+
+ glm::vec3 second, third;
+
+ if (offset[0].x >= offset[0].y) {
+ if (offset[0].y >= offset[0].z) {
+ second = { 1.0f, 0.0f, 0.0f };
+ third = { 1.0f, 1.0f, 0.0f };
+ } else if (offset[0].x >= offset[0].z) {
+ second = { 1.0f, 0.0f, 0.0f };
+ third = { 1.0f, 0.0f, 1.0f };
+ } else {
+ second = { 0.0f, 0.0f, 1.0f };
+ third = { 1.0f, 0.0f, 1.0f };
+ }
+ } else if (offset[0].y < offset[0].z) {
+ second = { 0.0f, 0.0f, 1.0f };
+ third = { 0.0f, 1.0f, 1.0f };
+ } else if (offset[0].x < offset[0].z) {
+ second = { 0.0f, 1.0f, 0.0f };
+ third = { 0.0f, 1.0f, 1.0f };
+ } else {
+ second = { 0.0f, 1.0f, 0.0f };
+ third = { 1.0f, 1.0f, 0.0f };
+ }
+
+ offset[1] = offset[0] - second + glm::vec3(1.0f/6.0f);
+ offset[2] = offset[0] - third + glm::vec3(1.0f/3.0f);
+ offset[3] = offset[0] - glm::vec3(0.5f);
+
+ size_t index[3] = {
+ unsigned(skewed.x) % 256,
+ unsigned(skewed.y) % 256,
+ unsigned(skewed.z) % 256,
+ };
+ size_t corner[4] = {
+ Perm(index[0] + Perm(index[1] + Perm(index[2]))),
+ Perm(index[0] + second.x + Perm(index[1] + second.y + Perm(index[2] + second.z))),
+ Perm(index[0] + third.x + Perm(index[1] + third.y + Perm(index[2] + third.z))),
+ Perm(index[0] + 1 + Perm(index[1] + 1 + Perm(index[2] + 1))),
+ };
+ float n[4];
+ float t[4];
+ for (size_t i = 0; i < 4; ++i) {
+ t[i] = 0.6f - dot(offset[i], offset[i]);
+ if (t[i] < 0.0f) {
+ n[i] = 0.0f;
+ } else {
+ t[i] *= t[i];
+ n[i] = t[i] * t[i] * dot(Grad(corner[i]), offset[i]);
+ }
+ }
+
+ return 32.0f * (n[0] + n[1] + n[2] + n[3]);
+}
+
+
+unsigned char SimplexNoise::Perm(size_t idx) const {
+ return perm[idx % 256];
+}
+
+const glm::vec3 &SimplexNoise::Grad(size_t idx) const {
+ return grad[idx % 12];
+}
+
+}