Add multithreaded ray tracer implementation

include/rtweekend.h

@@ -0,0 +1,45 @@
+#ifndef RTWEEKEND_H
+#define RTWEEKEND_H
+
+#include <cmath>
+#include <random>
+#include <iostream>
+#include <limits>
+#include <memory>
+
+
+// C++ Std Usings
+
+using std::make_shared;
+using std::shared_ptr;
+
+// Constants
+
+const double infinity = std::numeric_limits<double>::infinity();
+const double pi = 3.1415926535897932385;
+
+// Utility Functions
+
+inline double degrees_to_radians(double degrees) {
+    return degrees * pi / 180.0;
+}
+inline double random_double() {
+    thread_local static std::mt19937 generator(std::random_device{}());
+    thread_local static std::uniform_real_distribution<double> distribution(0.0, 1.0);
+    return distribution(generator);
+}
+
+
+inline double random_double(double min, double max) {
+    // Returns a random real in [min,max).
+    return min + (max-min)*random_double();
+}
+
+// Common Headers
+
+#include "color.h"
+#include "interval.h"
+#include "ray.h"
+#include "vec3.h"
+
+#endif