text: #include "util.h"
  #include <math.h>
  
  double uniform_random()
  {
  	return (double)std::rand() / (double)RAND_MAX;
  }
  
  vec2 uniform_random_vec2()
  {
  	float X1 = uniform_random();
  	float X2 = uniform_random();
  	return vec2(X1, X2);
  }
  
  vec2 sample_circle()
  {
  	float r = uniform_random();
  	float thetha = uniform_random() * 2 * M_PI;
  	return vec2(r * sin(thetha), r * cos(thetha));
  }
  