mandelbrot.cpp

#include <ecs/ecs.h>
#include <complex>
#include <iostream>

// Based on https://solarianprogrammer.com/2013/02/28/mandelbrot-set-cpp-11/

constexpr int dimension = 500;

struct pos {
	int x, y;
};

void mandelbrot_system(size_t& color, pos const& p) {
	int constexpr max_iterations = 500;
	double constexpr fr_w = 1.5;
	double constexpr fr_h = 1.5;
	double constexpr fr_x = -2.2;
	double constexpr fr_y = 1.2;

	std::complex<double> c(static_cast<double>(p.x), static_cast<double>(p.y));

	// Convert a pixel coordinate to the complex domain
	c = {c.real() / (double)dimension * fr_w + fr_x, c.imag() / (double)dimension * fr_h + fr_y};

	// Check if a point is in the set or escapes to infinity
	std::complex<double> z(0);
	size_t iter = 0;
	while (abs(z) < 3.0 && iter < max_iterations) {
		z = z * z + c;
		iter++;
	}

	color += iter;
}

int main() {
	ecs::runtime rt;
	// Add the system
	rt.make_system(mandelbrot_system);

	// Add the size_t component to the pixels/entities
	ecs::entity_range const ents{0, dimension * dimension - 1};
	rt.add_component(ents, size_t{0});
	rt.add_component_generator(ents, [](ecs::entity_id ent) -> pos {
		int const x = ent % dimension;
		int const y = ent / dimension;
		return {x, y};
	});

	// Commit all component changes and run the system
	rt.update();

	// Count the pixels equal to one
	size_t counter = 0;
	for (size_t const& color : rt.get_components<size_t>(ents))
		if (color == 1)
			counter++;

	std::cout << counter << " pixels with a value of 1\n";
}