main.cpp

#include <iostream>
#include <chrono>
#include <thread>

using std::cout;

void f() {
    std::chrono::seconds sleep_time(1);
    while (1) {
        cout << "rendering...\n";
        std::this_thread::sleep_for(sleep_time);
    }
}

int main() {
    cout << "1\n";
    cout << "2\n";
    std::thread t(f);
    cout << "3\n";
    cout << "4\n";
    return 0;
}