graphics/fractal.cpp
/*******************************************************
* Copyright (c) 2014, ArrayFire
* All rights reserved.
*
* This file is distributed under 3-clause BSD license.
* The complete license agreement can be obtained at:
* https://arrayfire.com/licenses/BSD-3-Clause
********************************************************/
#include <arrayfire.h>
#include <stdio.h>
#include <cmath>
#include <cstdlib>
#include <iostream>
#define WIDTH 400 // Width of image
#define HEIGHT 400 // Width of image
using namespace af;
using std::abs;
array complex_grid(int width, int height, float zoom, float center[2]) {
// Generate sequences of length width, height
array X =
(iota(dim4(1, height), dim4(width, 1)) - (float)height / 2.0) / zoom +
center[0];
array Y =
(iota(dim4(width, 1), dim4(1, height)) - (float)width / 2.0) / zoom +
center[1];
// Return the locations as a complex grid
return complex(X, Y);
}
array mandelbrot(const array &in, int iter, float maxval) {
array C = in;
array Z = C;
array mag = constant(0, C.dims());
for (int ii = 1; ii < iter; ii++) {
// Do the calculation
Z = Z * Z + C;
// Get indices where abs(Z) crosses maxval
array cond = (abs(Z) > maxval).as(f32);
mag = af::max(mag, cond * ii);
// If abs(Z) cross maxval, turn off those locations
C = C * (1 - cond);
Z = Z * (1 - cond);
// Ensuring the JIT does not become too large
af::eval(C, Z);
mag.eval();
}
// Normalize
return mag / maxval;
}
array normalize(array a) {
float mx = af::max<float>(a);
float mn = af::min<float>(a);
return (a - mn) / (mx - mn);
}
int main(int argc, char **argv) {
int device = argc > 1 ? atoi(argv[1]) : 0;
int iter = argc > 2 ? atoi(argv[2]) : 100;
bool console = argc > 2 ? argv[2][0] == '-' : false;
try {
af::setDevice(device);
info();
printf("** ArrayFire Fractals Demo **\n");
af::Window wnd(WIDTH, HEIGHT, "Fractal Demo");
float center[] = {-0.75f, 0.1f};
// Keep zomming out for each frame
for (int i = 10; i < 400; i++) {
int zoom = i * i;
if (!(i % 10)) {
printf("iteration: %d zoom: %d\n", i, zoom);
fflush(stdout);
}
// Generate the grid at the current zoom factor
array c = complex_grid(WIDTH, HEIGHT, zoom, center);
iter = sqrt(abs(2 * sqrt(abs(1 - sqrt(5 * zoom))))) * 100;
// Generate the mandelbrot image
array mag = mandelbrot(c, iter, 1000);
if (!console) {
if (wnd.close()) break;
array mag_norm = normalize(mag);
wnd.image(mag_norm);
}
}
} catch (af::exception &e) {
fprintf(stderr, "%s\n", e.what());
throw;
}
return 0;
}