Method noiseXYZ

Source/Utils/SimplexNoise.cpp:303–397

* 3D Perlin simplex noise * * @param[in] x float coordinate * @param[in] y float coordinate * @param[in] z float coordinate * * @return Noise value in the range[-1; 1], value of 0 on all integer coordinates. */

 * @return Noise value in the range[-1; 1], value of 0 on all integer coordinates.
 */
float SimplexNoise::noiseXYZ(float x, float y, float z) {
    float n0, n1, n2, n3; // Noise contributions from the four corners

    // Skewing/Unskewing factors for 3D
    static const float F3 = 1.0f / 3.0f;
    static const float G3 = 1.0f / 6.0f;

    // Skew the input space to determine which simplex cell we're in
    float s = (x + y + z) * F3; // Very nice and simple skew factor for 3D
    int i = fastfloor(x + s);
    int j = fastfloor(y + s);
    int k = fastfloor(z + s);
    float t = (i + j + k) * G3;
    float X0 = i - t; // Unskew the cell origin back to (x,y,z) space
    float Y0 = j - t;
    float Z0 = k - t;
    float x0 = x - X0; // The x,y,z distances from the cell origin
    float y0 = y - Y0;
    float z0 = z - Z0;

    // For the 3D case, the simplex shape is a slightly irregular tetrahedron.
    // Determine which simplex we are in.
    int i1, j1, k1; // Offsets for second corner of simplex in (i,j,k) coords
    int i2, j2, k2; // Offsets for third corner of simplex in (i,j,k) coords
    if (x0 >= y0) {
        if (y0 >= z0) {
            i1 = 1; j1 = 0; k1 = 0; i2 = 1; j2 = 1; k2 = 0; // X Y Z order
        } else if (x0 >= z0) {
            i1 = 1; j1 = 0; k1 = 0; i2 = 1; j2 = 0; k2 = 1; // X Z Y order
        } else {
            i1 = 0; j1 = 0; k1 = 1; i2 = 1; j2 = 0; k2 = 1; // Z X Y order
        }
    } else { // x0<y0
        if (y0 < z0) {
            i1 = 0; j1 = 0; k1 = 1; i2 = 0; j2 = 1; k2 = 1; // Z Y X order
        } else if (x0 < z0) {
            i1 = 0; j1 = 1; k1 = 0; i2 = 0; j2 = 1; k2 = 1; // Y Z X order
        } else {
            i1 = 0; j1 = 1; k1 = 0; i2 = 1; j2 = 1; k2 = 0; // Y X Z order
        }
    }

    // A step of (1,0,0) in (i,j,k) means a step of (1-c,-c,-c) in (x,y,z),
    // a step of (0,1,0) in (i,j,k) means a step of (-c,1-c,-c) in (x,y,z), and
    // a step of (0,0,1) in (i,j,k) means a step of (-c,-c,1-c) in (x,y,z), where
    // c = 1/6.
    float x1 = x0 - i1 + G3; // Offsets for second corner in (x,y,z) coords
    float y1 = y0 - j1 + G3;
    float z1 = z0 - k1 + G3;
    float x2 = x0 - i2 + 2.0f * G3; // Offsets for third corner in (x,y,z) coords
    float y2 = y0 - j2 + 2.0f * G3;
    float z2 = z0 - k2 + 2.0f * G3;
    float x3 = x0 - 1.0f + 3.0f * G3; // Offsets for last corner in (x,y,z) coords
    float y3 = y0 - 1.0f + 3.0f * G3;
    float z3 = z0 - 1.0f + 3.0f * G3;

    // Work out the hashed gradient indices of the four simplex corners
    int gi0 = hash(i + hash(j + hash(k)));