snoise16() [1/4]

fl::u16 snoise16

(

fl::u32

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 106 of file simplex.cpp.hpp.

                        {
    fl::u32 i0 = x >> 12;
    fl::u32 i1 = i0 + 1;
    fl::i32 x0 = x & 0xfff;   // .12
    fl::i32 x1 = x0 - 0x1000; // .12
 
    fl::i32 t0 = 0x8000 - ((x0*x0)>>9);             // .15
    t0 = (t0 * t0) >> 15;                           // .15
    t0 = (t0 * t0) >> 15;                           // .15
    fl::i32 n0 = (t0 * grad(SIMPLEX_P(i0&0xff), x0)) >> 12; // .15 * .12 = .15
 
    fl::i32 t1 = 0x8000 - ((x1*x1)>>9);             // .15
    t1 = (t1 * t1) >> 15;                           // .15
    t1 = (t1 * t1) >> 15;                           // .15
    fl::i32 n1 = (t1 * grad(SIMPLEX_P(i1&0xff), x1)) >> 12; // .15 * .12 = .15
 
    fl::i32 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 fl::u16(n) + 0x8000;
}

References grad(), SIMPLEX_P, and x.

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