inoise16_raw() [2/4]

int16_t inoise16_raw ( uint32_t x, uint32_t y )

extern

16-bit, fixed point implementation of Perlin's noise without scaling.

Coordinates are 16.16 fixed point values, 32 bit integers with integral coordinates in the high 16-bits and fractional in the low 16-bits.

Returns

unscaled noise value as a signed integer, roughly -18k to 18k

Parameters

x	x-axis coordinate on noise map (1D)
y	y-axis coordinate on noise map (2D)

Definition at line 472 of file noise.cpp.

{
    // Find the unit cube containing the point
    uint8_t X = x>>16;
    uint8_t Y = y>>16;
 
    // Hash cube corner coordinates
    uint8_t A = P(X)+Y;
    uint8_t AA = P(A);
    uint8_t AB = P(A+1);
    uint8_t B = P(X+1)+Y;
    uint8_t BA = P(B);
    uint8_t BB = P(B+1);
 
    // Get the relative position of the point in the cube
    uint16_t u = x & 0xFFFF;
    uint16_t v = y & 0xFFFF;
 
    // Get a signed version of the above for the grad function
    int16_t xx = (u >> 1) & 0x7FFF;
    int16_t yy = (v >> 1) & 0x7FFF;
    uint16_t N = 0x8000L;
 
    u = EASE16(u); v = EASE16(v);
 
    int16_t X1 = LERP(grad16(P(AA), xx, yy), grad16(P(BA), xx - N, yy), u);
    int16_t X2 = LERP(grad16(P(AB), xx, yy-N), grad16(P(BB), xx - N, yy - N), u);
 
    int16_t ans = LERP(X1,X2,v);
 
    return ans;
}

References grad16(), P, x, and y.

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