2D raw Simplex noise
| 82 | |
| 83 | // 2D raw Simplex noise |
| 84 | float SimplexRawNoise(const float x, const float y) { |
| 85 | // Noise contributions from the three corners |
| 86 | float n0, n1, n2; |
| 87 | // Skew the input space to determine which simplex cell we're in |
| 88 | float F2 = 0.5f * (sqrtf(3.0f) - 1.0f); |
| 89 | // Hairy factor for 2D |
| 90 | float s = (x + y) * F2; |
| 91 | int i = fastfloor( x + s ); |
| 92 | int j = fastfloor( y + s ); |
| 93 | float G2 = (3.0f - sqrtf(3.0f)) / 6.0f; |
| 94 | float t = (i + j) * G2; |
| 95 | // Unskew the cell origin back to (x,y) space |
| 96 | float X0 = i-t; |
| 97 | float Y0 = j-t; |
| 98 | // The x,y distances from the cell origin |
| 99 | float x0 = x-X0; |
| 100 | float y0 = y-Y0; |
| 101 | // For the 2D case, the simplex shape is an equilateral triangle. |
| 102 | // Determine which simplex we are in. |
| 103 | int i1, j1; // Offsets for second (middle) corner of simplex in (i,j) coords |
| 104 | if(x0>y0) {i1=1; j1=0;} // lower triangle, XY order: (0,0)->(1,0)->(1,1) |
| 105 | else {i1=0; j1=1;} // upper triangle, YX order: (0,0)->(0,1)->(1,1) |
| 106 | // A step of (1,0) in (i,j) means a step of (1-c,-c) in (x,y), and |
| 107 | // a step of (0,1) in (i,j) means a step of (-c,1-c) in (x,y), where |
| 108 | // c = (3-sqrt(3))/6 |
| 109 | float x1 = x0 - i1 + G2; // Offsets for middle corner in (x,y) unskewed coords |
| 110 | float y1 = y0 - j1 + G2; |
| 111 | float x2 = x0 - 1.0f + 2.0f * G2; // Offsets for last corner in (x,y) unskewed coords |
| 112 | float y2 = y0 - 1.0f + 2.0f * G2; |
| 113 | // Work out the hashed gradient indices of the three simplex corners |
| 114 | int ii = i & 255; |
| 115 | int jj = j & 255; |
| 116 | int gi0 = perm[ii+perm[jj]] % 12; |
| 117 | int gi1 = perm[ii+i1+perm[jj+j1]] % 12; |
| 118 | int gi2 = perm[ii+1+perm[jj+1]] % 12; |
| 119 | // Calculate the contribution from the three corners |
| 120 | float t0 = 0.5f - x0*x0-y0*y0; |
| 121 | if(t0<0) n0 = 0.0f; |
| 122 | else { |
| 123 | t0 *= t0; |
| 124 | n0 = t0 * t0 * dot(grad3[gi0], x0, y0); // (x,y) of grad3 used for 2D gradient |
| 125 | } |
| 126 | float t1 = 0.5f - x1*x1-y1*y1; |
| 127 | if(t1<0) n1 = 0.0f; |
| 128 | else { |
| 129 | t1 *= t1; |
| 130 | n1 = t1 * t1 * dot(grad3[gi1], x1, y1); |
| 131 | } |
| 132 | float t2 = 0.5f - x2*x2-y2*y2; |
| 133 | if(t2<0) n2 = 0.0f; |
| 134 | else { |
| 135 | t2 *= t2; |
| 136 | n2 = t2 * t2 * dot(grad3[gi2], x2, y2); |
| 137 | } |
| 138 | // Add contributions from each corner to get the final noise value. |
| 139 | // The result is scaled to return values in the interval [-1,1]. |
| 140 | return 70.0f * (n0 + n1 + n2); |
| 141 | } |
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