8 constexpr float one_third = 1.0f/3.0f;
9 constexpr float one_sixth = 1.0f/6.0f;
15 SimplexNoise::SimplexNoise(unsigned int seed)
18 { -1.0f, 1.0f, 0.0f },
19 { 1.0f, -1.0f, 0.0f },
20 { -1.0f, -1.0f, 0.0f },
22 { -1.0f, 0.0f, 1.0f },
23 { 1.0f, 0.0f, -1.0f },
24 { -1.0f, 0.0f, -1.0f },
26 { 0.0f, -1.0f, 1.0f },
27 { 0.0f, 1.0f, -1.0f },
28 { 0.0f, -1.0f, -1.0f },
30 unsigned int val = seed;
31 for (size_t i = 0; i < 256; ++i) {
32 val = 2346765 * val + 6446345;
34 perm[i + 256] = perm[i];
39 float SimplexNoise::operator ()(const glm::vec3 &in) const {
40 float skew = (in.x + in.y + in.z) * one_third;
42 glm::vec3 skewed(glm::floor(in + skew));
43 float tr = (skewed.x + skewed.y + skewed.z) * one_sixth;
45 glm::vec3 unskewed(skewed - tr);
47 offset[0] = in - unskewed;
49 glm::vec3 second, third;
51 if (offset[0].x >= offset[0].y) {
52 if (offset[0].y >= offset[0].z) {
53 second = { 1.0f, 0.0f, 0.0f };
54 third = { 1.0f, 1.0f, 0.0f };
55 } else if (offset[0].x >= offset[0].z) {
56 second = { 1.0f, 0.0f, 0.0f };
57 third = { 1.0f, 0.0f, 1.0f };
59 second = { 0.0f, 0.0f, 1.0f };
60 third = { 1.0f, 0.0f, 1.0f };
62 } else if (offset[0].y < offset[0].z) {
63 second = { 0.0f, 0.0f, 1.0f };
64 third = { 0.0f, 1.0f, 1.0f };
65 } else if (offset[0].x < offset[0].z) {
66 second = { 0.0f, 1.0f, 0.0f };
67 third = { 0.0f, 1.0f, 1.0f };
69 second = { 0.0f, 1.0f, 0.0f };
70 third = { 1.0f, 1.0f, 0.0f };
73 offset[1] = offset[0] - second + one_sixth;
74 offset[2] = offset[0] - third + one_third;
75 offset[3] = offset[0] - 0.5f;
77 unsigned char index[3] = {
78 (unsigned char)(skewed.x),
79 (unsigned char)(skewed.y),
80 (unsigned char)(skewed.z),
83 Perm(index[0] + Perm(index[1] + Perm(index[2]))),
84 Perm(index[0] + second.x + Perm(index[1] + second.y + Perm(index[2] + second.z))),
85 Perm(index[0] + third.x + Perm(index[1] + third.y + Perm(index[2] + third.z))),
86 Perm(index[0] + 1 + Perm(index[1] + 1 + Perm(index[2] + 1))),
90 for (size_t i = 0; i < 4; ++i) {
91 t[i] = 0.6f - dot(offset[i], offset[i]);
96 n[i] = t[i] * t[i] * dot(Grad(corner[i]), offset[i]);
100 return 32.0f * (n[0] + n[1] + n[2] + n[3]);
104 unsigned char SimplexNoise::Perm(size_t idx) const {
108 const glm::vec3 &SimplexNoise::Grad(size_t idx) const {
109 return grad[idx % 12];