C++ Program using ArrayFire that show cases Perlin Noise Generation using GPU.

perlin_noise.cpp

/*******************************************************
 * Copyright (c) 2017, ArrayFire
 * All rights reserved.
 *
 * This file is distributed under 3-clause BSD license.
 * The complete license agreement can be obtained at:
 * http://arrayfire.com/licenses/BSD-3-Clause
 ********************************************************/

#include <arrayfire.h>
#include <cstdio>
#include <cstdlib>

using namespace af;

array perlin(int w, int h)
{
    const float PERSISTENCE = 0.5f;

    array base   = randu(w, h);
    array perlin = constant(0.0f, w, h);
    float amp    = 1.0f;
    float samp   = 0.0f;

    for (int octave=6; octave>=0; --octave) {
        float period = float(1 << octave);
        float freq = 1.0f/period;

        array x = iota(dim4(w, 1)); // Coloumn Vector
        array y = iota(dim4(1, h)); // Row Vector

        // Generate horizontal indices to sample data
        // for interpolation w.r.t current period
        array si0 = (x / period).as(s32) * period; 
        array si1 = (si0 + period).as(s32) % w;
        array hblend = (x - si0) * freq;
        hblend = tile(hblend, dim4(1, h)); // tile data along second dimension to enable use in equations that expect matrices

        // Generate horizontal indices to sample data
        // for interpolation w.r.t current period
        array sj0 = (y / period).as(s32) * period;
        array sj1 = (sj0 + period).as(s32) % h;
        array vblend = (y - sj0) * freq;
        vblend = tile(vblend, dim4(w, 1)); // tile data along first dimension to enable use in equations that expect matrices

        array top = base(si0, sj0)*(1.0f-hblend) + hblend*base(si1, sj0); // base(array, array)
        array bot = base(si0, sj1)*(1.0f-hblend) + hblend*base(si1, sj1); // use indices generated to sample base noise
        array blend = top*(1.0f-vblend) + vblend*bot; //interpolate all values

        perlin += (amp*blend); //scale by amplitude and add to perlin noise accumulator

        samp += amp;
        amp *= PERSISTENCE;
    }

    return perlin/samp;
}

int main(int argc, char *argv[])
{
    try {

        int device = argc > 1 ? atoi(argv[1]) : 0;
        af::setDevice(device);
        af::info();

        af::Window w(640, 640);

        while(!w.close())
            w.image(perlin(256, 256));

    } catch (af::exception& e) {

        fprintf(stderr, "%s\n", e.what());
        throw;
    }

    return 0;
}

@9prady9

• x,y can go outside the for loop
• generate x,y as s32
• period can be int (if x and y are s32)
• remove .as(s32) for si0, si1, sj0, sj1