snoise16() [1/4]

uint16_t snoise16

(

uint32_t

x

)

32 bit, fixed point implementation of simplex noise functions.

The inputs are 20.12 fixed-point value. The result covers the full range of a uint16_t averaging around 32768.

Definition at line 102 of file simplex.cpp.

                              {
    uint32_t i0 = x >> 12;
    uint32_t i1 = i0 + 1;
    int32_t x0 = x & 0xfff;   // .12
    int32_t x1 = x0 - 0x1000; // .12
 
    int32_t t0 = 0x8000 - ((x0*x0)>>9);             // .15
    t0 = (t0 * t0) >> 15;                           // .15
    t0 = (t0 * t0) >> 15;                           // .15
    int32_t n0 = (t0 * grad(P(i0&0xff), x0)) >> 12; // .15 * .12 = .15
 
    int32_t t1 = 0x8000 - ((x1*x1)>>9);             // .15
    t1 = (t1 * t1) >> 15;                           // .15
    t1 = (t1 * t1) >> 15;                           // .15
    int32_t n1 = (t1 * grad(P(i1&0xff), x1)) >> 12; // .15 * .12 = .15
 
    int32_t n = n0 + n1;   // .15
    n += 2503;             // .15: fix offset, adjust to +0.03
    n = (n * 26694) >> 16; // .15: fix scale to fit in [-1,1]
    return uint16_t(n) + 0x8000;
}

References grad(), P, and x.

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